Design and prototype of a capillary blood sampler at Radiometer … · Radiometer is a global provider of high technological solutions for acute care diagnostics in blood gas testing,

Design and prototype of a capillary blood

sampler at Radiometer Medical ApS

BSc Thesis, June 2013

Fehmi Yetik, s083668

CONFIDENTIAL

Academic Supervisor Company Supervisor Associate Professor Guido Tosello Mechanic manager Lars Friis Professor Leonardo De Chiffre

https://www.campusnet.dtu.dk/cnnet/participants/showperson.aspx?id=996&elementid=401807




BSc thesis Confidential June 2013 Fehmi Yetik s083668

2 1: Arteries are blood vessels that carry blood rich in oxygen throughout your body

2: The queue functionality module automatically identifies mixes and measures up to the samples in succession. Samples are automatically conveyed to the inlet and aspirated into the analyzer.

Abstract This BCs thesis project is based on design and prototype of a micro arterial1 capillary sampler

(micro sampler) for blood gas analyzers at Radiometer Medical ApS (Radiometer).

Radiometer is a global provider of high technological solutions for acute care diagnostics in

blood gas testing, immunoassay testing, and transcutaneous. This project is based on the

development of a micro sampler solution to the queue function2 of the new blood gas

analyzer (ABL 900) which is planned launching in 2014, and for the current blood gas

analyzed at Radiometer (ABL90).

An important motivation for Radiometer is that the new micro sampler is based on a

previous generation of samplers. So it is possible to carry-over core modules from the

previous generation to the new one. In this way the time-to-market decreases and the

quality increases.

Therefore it is tried to reuse lots of the components and interfaces from the old samplers, in

the new sampler, e.g. the needle, the magnet, the 1D barcode and the interfaces from old

products/samplers.

The best concept is found during the concept generation and it is further improved with

design calculation. Accordingly, it is shown by injection molding simulation that the parts of

the micro sampler with the chosen polymer materials can be molded. To ensure that the

parts of the micro sampler can be measured same way every time, the technician drawing of

the parts are specified by Geometrical Product Specification (GPS). In this way the quality of

the parts increases. In addition the risk of potential failures for the micro sampler is reduced

before reaching the customer by using the Failure Mode and Effects Analysis (FMEA).

Furthermore this project has completed a research and diagnosis phase where four essential

tests have been clarified:

Functionality test of the micro sampler which consists of filter test and draw test

into the blood gas analyzer (ABL90).

Mixing test.

Usability test on hospital.

The conclusion of these tests shows that the micro sampler is able to be used with benefit by

Radiometer in the future.


3

Preface This report makes up the thesis of graduate diplom Eng. degree project performed at the

Technical University of Denmark (DTU), Mechanical Engineering – Department of

Manufacturing Engineering.

The project has been carried out in close cooperation with Radiometer Medical ApS

(Radiometer) and DTU. The project was initiated the first week of February 2013 and finished

the last week of May 2013. The extent of the project corresponds to 20 ECTS point.

I want to give special thanks to all who supported me by realization of the project. Special

thanks go to my company supervisor Lars Friis for putting many valuable hours into providing

guidance throughout the project. Also special thanks to my DTU supervisor Guido Tosello for

his valuable guidance and encouragement throughout the project. Furthermore I would like

to give thanks to Professor Leonardo De Chiffre, Jakob Rasmussen and all the Radiometer

employees who have supported me in this project.

Fehmi Yetik

Copenhagen, June 2013


4

Contents

Abstract ............................................................................................................................................................. 2

Preface ............................................................................................................................................................... 3

1. Introduction ............................................................................................................................................... 9

1.2 Company Introduction: Radiometer Medical ApS ............................................................................. 9

1.3 Project Background ........................................................................................................................... 9

1.4 Project challenges .............................................................................................................................. 9

1.5 Problem Statement ......................................................................................................................... 10

1.6 Requirements to the micro sampler ............................................................................................... 11

1.7 Interfaces specification of the sampler ........................................................................................... 12

1.7.1 Interfaces between the sampler and the probe of the blood analyze ......................................... 12

1.7.2 Interfaces between the micro sampler and the slot .................................................................... 13

1.8 Interfaces description of user .......................................................................................................... 14

1.9 Interfaces description of production ............................................................................................... 15

2. Concept phase ......................................................................................................................................... 16

2.2 Pre-design concept .......................................................................................................................... 16

2.2.1 Concept 1 simple manual sampler with plug solution ............................................................ 17

2.2.2 Concept 2 semi-automatic sampler with filter solution ............................................................... 18

2.2.3 Concept 3 semi-automatic sampler with button solution ............................................................ 19

2.2.4 Concept 4 manual sampler with screw solution........................................................................... 20

2.2.5 Concept 5 semi-automatic sampler with ejected needle system................................................. 21

2.2.6 Concept 6 semi-automatic sampler with two side solution ......................................................... 22

2.2.7 Concept 7 semi-automatic sampler with luer in the middle ........................................................ 23

2.3 Morphological analysis .................................................................................................................... 24

2.3.1 Systematically comparing the pairs of objectives ................................................................... 24

2.3.2 One side solution ..................................................................................................................... 25

2.3.3 The two side solution .............................................................................................................. 26

2.3.4 Middle side solution ................................................................................................................ 27

2.4 Evaluate by design criteria............................................................................................................... 28

2.5 The final concept ............................................................................................................................. 28

2.5.1 Chosen concept semi-automatic micro sampler with slider solution ..................................... 28

2.6 Prototype of the chosen design concept ......................................................................................... 30


5

2.6.1 Simulation the using procedure of the prototype ................................................................... 31

2.6.2 User requirements ................................................................................................................... 32

2.6.3 User team ................................................................................................................................ 33

2.6.4 Feedback from the users ......................................................................................................... 34

2.7 Version 2 of the concept ................................................................................................................. 35

2.8 Prototype of design concept version 2 ............................................................................................ 36

2.8.1 Simulate the producer of the prototype ................................................................................. 36

2.8.2 Feedback from the user team to version 2 ............................................................................. 37

2.8.3 Mixing test ............................................................................................................................... 38

2.9 Comparison of the samplers............................................................................................................ 39

2.10 Conclusion ....................................................................................................................................... 39

3. Material selection .................................................................................................................................... 40

3.1 Loadings analyzing to the sampler .................................................................................................. 40

3.2 Material selection bottom cover ..................................................................................................... 40

3.3 Material selection for top cover ...................................................................................................... 43

3.4 Further work for PETG ..................................................................................................................... 47

3.5 Material selection for the filter, rubber caps and mixer pin ........................................................... 48

3.6 Summary and conclusion................................................................................................................. 48

4. Calculations and dimensioning ................................................................................................................ 49

4.1 Design improvement and calculation .............................................................................................. 49

4.1.1 Press fit calculation for the luer cap ........................................................................................ 51

4.1.2 Snap fits calculation ................................................................................................................. 52

4.1.3 Integral hinge calculation ........................................................................................................ 52

4.1.4 Length calculation of capillary wire ......................................................................................... 53

4.1.5 Diffusion calculation of the capillary sampler ......................................................................... 53

4.1.6 Surface tension calculation...................................................................................................... 54

4.2 Injection molding Process calculation ............................................................................................. 55

4.2.1 Ram position calculation ......................................................................................................... 55

4.2.2 Cooling time calculation .......................................................................................................... 56

4.2.3 The packing time calculation ................................................................................................... 56

4.2.4 Pressure drop calculation ........................................................................................................ 58

4.2.5 Clamp force, fill time and packing pressure calculation .......................................................... 60

4.2.6 Cycle time calculation .............................................................................................................. 60


6

4.3 Cost calculation and mold design specification............................................................................... 61

4.3.1 Cavity number calculation ....................................................................................................... 61

4.3.2 Productions cost ...................................................................................................................... 64

4.4 Mold design specification ................................................................................................................ 65

4.4.1 Mold cavities design ................................................................................................................ 65

4.4.2 Mold gate design ..................................................................................................................... 66

4.4.3 Mold specification ................................................................................................................... 67

4.4.4 Maintenance of the molds ...................................................................................................... 68

4.5 Mechanical calculation of the micro sampler structure .................................................................. 69

4.5.1 The loading situation during assembly .................................................................................... 69

4.5.2 The reaction force during unavoidable mishaps as fall from hand ......................................... 69

4.5.3 Stress during transports the sampler ...................................................................................... 71

4.6 Mechanical simulation..................................................................................................................... 73

4.6.1 The maximum pull force before twisting the bottom cover. .................................................. 73

4.6.2 Maximum twist angles of the top cover .................................................................................. 74

4.6.3 Maximum deflection on the capillary wire.............................................................................. 76

4.6.4 Maximum press on the capillary wire ..................................................................................... 77

4.6.5 Maximum press on the head of top cover .............................................................................. 78

4.7 Conclusion and summary ................................................................................................................ 79

5. Injection molding simulation ................................................................................................................... 80

5.1 Simulation top cover ....................................................................................................................... 80

5.1.1 Fill shot series for top cover .................................................................................................... 80

5.1.2 Packing pressure series for top cover ...................................................................................... 83

5.1.3 Packing time series for top cover ............................................................................................ 87

5.1.4 Cooling time series for top cover ............................................................................................ 89

5.1.5 Optimization series for top cover ............................................................................................ 90

5.2 Simulation bottom cover ................................................................................................................. 90

5.2.1 Fill shot series bottom cover ................................................................................................... 90

5.2.2 Packing pressure series for bottom cover ............................................................................... 93

5.2.3 Packing time series .................................................................................................................. 97

5.2.4 Cooling time series .................................................................................................................. 99

5.2.5 Optimization series ................................................................................................................ 100

5.3 Theoretical Process set up table .................................................................................................... 100


7

5.3.1 Theoretical process set up table for top cover ...................................................................... 100

5.3.2 Theoretical process set up table for bottom cover ............................................................... 101

5.4 Quality control demands ............................................................................................................... 102

5.4.1 Process control requirement of top cover .................................................................................. 102

5.4.2 Process control requirement of bottom cover ........................................................................... 102

5.5 Comparison of materials ............................................................................................................... 103

5.5.1 Comparison viscosity .................................................................................................................. 103

5.5.2 Comparison specific volume ....................................................................................................... 104

5.6 The 6 Process parameters which have influenced on the molded part ........................................ 105

5.7 Conclusion and summary .............................................................................................................. 105

6. Geometrical product specification (GPS) .................................................................................................. 107

6.1 Introduction to GPS ....................................................................................................................... 107

6.1.1. ISO 14638 – Masterplan ........................................................................................................ 108

6.1.2. Functionality approach .......................................................................................................... 109

6.2 The skin model of GPS ................................................................................................................... 110

6.1.3. 14253-1 –Rules on conformity .............................................................................................. 111

6.3 The critical interfaces of the sampler ............................................................................................ 112

6.4 Tolerance chain calculation ........................................................................................................... 113

6.5 Demands for the sampler .............................................................................................................. 114

6.5.1 Design specification ............................................................................................................... 114

6.5.2 Requirement to Dimensision of the sampler parts .............................................................. 114

6.5.3 Requirement to surface of the parts .................................................................................... 115

6.6 Convert the demands of the sampler to GPS tolerance symbols.................................................. 115

6.7 Process window ............................................................................................................................. 116

6.8 Tolerancing indication on drawing ................................................................................................ 116

6.9 2D technical drawing of Top cover ................................................................................................ 117

6.10. 2D technical drawing of bottom cover ...................................................................................... 118

7. Test of sampler .......................................................................................................................................... 119

7.2 Functionality test of the micro sampler ........................................................................................ 119

7.2.1 Filter test ................................................................................................................................ 119

7.2.2 The draw test ......................................................................................................................... 122

7.2 Usability test on the hospital ......................................................................................................... 126

7.2.1 Questionnaire A –Needle shield from Radiometer ............................................................... 127


8

7.2.2 Questionnaire A –Radiometer sampler with VTC on ............................................................. 128

7.2.3 Questionnaire C –concept of design sampler ........................................................................ 129

7.3 Conclusion ..................................................................................................................................... 130

8 Failure Mode and Effect Analysis (FMEA) ................................................................................................. 131

8.1 The pre-work ..................................................................................................................................... 132

8.1.1 Identify the FMEA approach and scope ................................................................................ 132

8.1.2 Utilize boundary diagrams as needed ................................................................................... 133

8.1.3 Identify relevant prior history on product/process .................................................................... 134

8.1.4 Translate customer requirement into product design specifications or requirements ............. 134

8.1.5 Modify ranking criteria to be relevant to your business .............................................................. 134

8.2 FMEA of the micro sampler ........................................................................................................... 137

9. Discussion .............................................................................................................................................. 139

10. Conclusion ......................................................................................................................................... 140

11. Outlook .............................................................................................................................................. 141

12. References ......................................................................................................................................... 142


9

1. Introduction

1.2 Company Introduction: Radiometer Medical ApS

Radiometer Medical ApS (Radiometer) is a global provider of high technological solutions for acute care diagnostics in blood gas testing, immunoassay testing, and transcutaneous testing. The products are designed, developed, and assembled by Radiometer. In addition to the analyzers Radiometer provides IT solutions that integrate the analyzers into the hospital systems. The Radiometer headquarters is located in Copenhagen, Denmark. On the development, manufacturing and sales side the company is represented globally. In 2004 the American conglomerate Danaher Corporation acquired Radiometer. Up until 2004 Radiometer was a Danish family-owned company. Radiometer has established a leading position in the market with more than 50 years of experience. The core business lies within blood gas analysis, while sale of analyzer consumables constitutes the greater part of their turnover. The Radiometer brand relies on high-class quality. In order to remain in a market leading position and to gain market share in emerging markets it is of outmost importance that Radiometer continues to provide high quality products with the right performance in the targeted markets.

1.3 Project Background The focus in this thesis is to design a micro arterial capillary sampler (micro sampler) without a plunger to draw smaller volumes of blood samples from the arterial blood vessels due to the target group of the sampler which is listed in the following:

Neonatal Intensive Care Unit (NICU) and Pediatric Intensive Care Unit (PICU)

Geriatrics patients

Cancer therapy patients

Cancer patients

The blood samples from NICU and PICU are always wanted in minimum blood volumes because these groups don’t have so much blood compared to adults. Moreover the cancer patients have lower red/white cell counts and low hemoglobin therefore it is difficult to draw blood samples with high volume. In addition the blood vessel of the cancer therapy patients are thin therefore it has a risk for collapse during drawing high blood samples.

1.4 Project challenges

The big challenges of the thesis are to design a new micro sampler with easy usability, better quality and good functionality and to realize that following experimental tests and theoretical study are planned: The theoretical work consists of:

Concept generation –The best concept will be found in systematic way during this study.

Material study- The best suitable thermoplastic material will be found in systematic way to the parts of the micro sampler.


10

Concept generation

Material selection

Calculations Mold flow

GPS -drawing

Test of the sampler

FMEA

Calculation & dimensions study – The final concept will be further optimized in relation to plastic design and it will be analysis for stress linked to improper use.

Injection molding simulation (mold flow)–The parts of the final concept will be simulated to make it clearly for the reader that the chosen concept and thermoplastics can be molded by injection molding.

Geometrical Production Specification (GPS) study –The technical drawing of the final concept parts will be indicated by GPS –drawing for lock the measurement technician to only measure the parts in one specific way.

Failure Mode and Effects Analysis (FMEA) –The risk of failure of the final concept will be reduced in systematic way.

The experimental works are listed in the following:

Usability test – The final concept is will be present for the users and based on their feedback the final concept will be further improved.

Mixing test – A simple model of final concept will be tested for it can mix the blood/fluid by magnet both manually and automatically.

Filter test – Two kinds of filters will be tested and based on their performance the best filter solution for blood will be choose.

Draw test- A simple model of final concept will be tested for how its draw the blood sample into blood gas analyzers (ABL 90). Further test results will be compared with the current capillary wire from Radiometer.

Usability test on hospital – The final concept will be present for nurses in the hospital and based on their feedback the final concept to micro sampler will be evaluated.

1.5 Problem Statement

Based on the project background and current situation at Radiometer the problem statement in the thesis has been to:

Design a micro sampler without a plunger to draw smaller volumes of blood samples from the

arterial blood vessels which is based on the previous generation sampler.

Figure 1 Project states


11

1.6 Requirements to the micro sampler

The requirements of the micro sampler are listed in the following:

Must be able to draw a blood sample from the arteries.

Must be possible to use both for A-puncture and A-line (needle attached for A-puncture and fit into A-line which is a medico device with opening and closing function, mounted on the hand of the patient )

Must fit in the mixer slot of the queue layer from ABL900.

The inner interfaces of the capillary blood sampler must guide the probe of the blood gas analyzers.

The micro sampler must be more user-friendly than a 1 mL sampler.

The inner interface of the sampler must be adapted with ABL90.

Must support the influx of the air while the sample is drawn into the blood gas analyzers.

Target volume of the capillary blood sampler must be 65µL.

Must be for single user.

Must be sterile i.e. including a process to kill bacteria.

The sampler must be adapted for transportation by pneumatic tube in the hospital.

Must be marked with 1D barcode.

The diffusion of the blood must change the pO2 of the sample less than 2% during

storage duration of 30 min.

Must have mixing ability without hemolysis i.e. loosing red blood cells in the blood

samples.

Sampler must contain heparin balanced for electrolytes (used to prevent a negative

bias in electrolyte concentrations in the syringes).

Must abide by the same test performance, storage and stability requirements as

valid for Pico50 or Pico70 (current syringes at Radiometer).

The syringe of the sampler should be delivered with a pre-attached holder (needle

plus needle shield).


12

Devise must ensure an air bubble free condition.

Must be packed on peel pack (packing machine) similar to other Radiometer Medical

ApS’ syringes.

Average selling price (ASP)at the same level as the PICO 70 (80 cent -1 dollar, based

on the US pricing)

1.7 Interfaces specification of the sampler

The description of the interfaces is very important when developing new modules of products

to make it possible to swap out one solution (e.g. one module) for another without affecting

the functionality (mechanical, optical, electronical and/or fluid) in the rest of the system.

Therefore Radiometer wishes interfaces descriptions for the micro sampler regarding to

design, user and production. The interfaces specification description for the micro sampler is

divided into two cases. The first case is the interface between the micro sampler and the

probe of the blood gas analyzer, and the second case is the interfaces between the mixer slot

of the queue layer and the micro sampler.

1.7.1 Interfaces between the sampler and the probe of the blood analyze

It is important to specify the interface between the probe and the micro sampler to ensure.

The probe can be guided into the micro sampler, and it has a support to the influx of the air

while the micro sampler is inserted into the blood analyzers ABL 90, ABL900 and the next

generation. Regardless the design of the micro sampler changes during the sampler life time

or not. Furthermore, the fluid properties have a big influence on the pre-analytical phase

(test analysis). Hence, there must be clearance between the magnet interface and inner

interface of the sampler for ensure that can it fulfill the mixing requirement.

The probe of the blood gas analyzer Micro Sampler

Interface specification

Geometrical condition

Probe guide interface to

ensure that the probe can find the hole of luer

Smooth surfaces to ensuresthat the probe can slide on the

surface

Avoid hole and airgap bigger than

0.9 mm on the guide surfaces to

avoid that the probe can fall in

Have an airgap between the

inner interfaces of the sampler

and the probe to ensure airflux

during sampling is drawn

Fluid flow condition

Analyzing 65 µl blood sample

during 35 without error in

the result

Figure 2 Interface illustration of micro sampler and probe of the blood gas analyzer


13

1.7.2 Interfaces between the micro sampler and the slot

The external diameter of the micro sampler must have same shape as the syringe to fit into

the slot. Furthermore the external diameter must dim the light from the slot of the queue

layer. In addition the micro sampler must be transparent, so the user can see when the

sampler is filled.

The slot of the queue

Micro sampler

Interface specification

Geometrical condition

Same interface as syringes Pico

70

Optical condition

Dim the light from sampler layer 50 %

The micro sampler must be

transparent

Diffusion

Chaning of PO2

and CO2 less than 2 % during

storage of the 30 min

Magnetism

The mixer pin must be

magnetic

Figure 3 Interface illustration of micro sampler and probe of the slot of the queue


14

1.8 Interfaces description of user

The user interface for the micro sampler should be specified to ensure that the user can

perform the operation easily. Luer and needle of the sampler must use as Pico 70 to make it

possible to draw a sample from the arteries and fit it into A-line. Furthermore the grip

handling of the micro sampler must be easy.

Needle accessory

Micro Sampler

User interface specification

Luer condition

The luer must have international standard

interface

Must be use with both for A-puncture

and A-line

Needle condition

Same needle version as Pico 70

Grip of sampler condition

Easy grip handling interface like Pico 70

Figure 4 Interface illustration of micro sampler and needle accessory


15

1.9 Interfaces description of production

The interface description of the production for the micro sampler should be specified to

ensure it can be packed on peel pack (packaging machine) similar to other Radiometer

syringes (Pico70 and Pico 50). The labeling with Radiometer logo and colors and 1 D barcode

must be as Pico70.

Production

Micro sampler

Production interface specification

Packaging

Packing on peel pack as the other syringes

Radiometer logo and color

Labeling with Radiometer logo and color as Pico 70

1 D barcode

1 D barcode similar to Pico 70

Figure 5 Interface illustration of the micro sampler and production


16

2. Concept phase In this chapter all concepts ideas to the micro sampler are developed, described and discussed. The design objectives which included technical and economic factors, user requirements,

and safety requirements are systematically comparing pairs one against the other. The

objective which has highest total scores is indicated as the highest priority objective. Based

on that, all the different solution ideas to the micro sampler are listed in a table and weighed

from a scale of 1-5. Subsequent, the best solution ideas which have gone further are

weighed in a table regarding to design criteria usability, price, mixing ability, manufacturing

and waste of blood. Finally, a final solution and a backup solution are chosen for the micro

sampler. The evaluation is performed by a team which consists of Radiometer employees.

2.2 Pre-design concept

All solution ideas are realized in CAD, described and discussed for advantages and

disadvantages before the morphological analysis, to obtain a better understanding and

picturing of the functionality, usability and difficulties of manufacturing.

Figure 6 Brainstorming to the luer solution performed by Radiometer team

Figure 7 Brainstorming to bottom solution performed by Radiometer team


17

2.2.1 Concept 1 simple manual sampler with plug solution

The first concept idea is designed very simple to give a good understanding of the

functionality. Concept 1 consists of two caps (top and bottom), fixed plastic part with probe

guide interface, magnet, capillary wire, external grip cover and needle include needle shield.

A short manual operation of the concept 1 is listed in the following:

After taking a sample the needled removed by the needle shield;

The bottom cap press on capillary wire;

The magnet insert into the capillary wire;

The upper cap press on capillary wire.

Advantages

Easy to use

Low cost prices

Less assembly parts

Disadvantages

Risk for blood waste during the mix

process

Risk for blood waste during sampling

Completely manual system

Figure 8 Left: Concept 1 before sampling. Right: Concept 1 after sampling

Figure 9 Concept 1 is put into the slot of the queue layer


18

2.2.2 Concept 2 semi-automatic sampler with filter solution

This concept idea is semi- automatic solution to the micro sampler and it is more user-

friendly than concept 1. Concept 2 consists of a filter, O-ring, bottom plastic part, top cap

with probe-guide surface, magnet, capillary wire, external grip cover and needle include

needle shield. The manual operation of this concept requires only two operations: after

taking a sample the needled removed by needle shield and the cap presses on the luer.


Figure 11 Left: The filter and cap of the concept 2. Right: Concept 2 is put into the slot of the queue layer


19

Advantages

Exact volume

Less manual operations

Low cost

More user-friendly than concept 1

Good mixing ability

2.2.3 Concept 3 semi-automatic sampler with button solution

This concept idea is semi-automatic solution to the micro sampler without filter. The idea is

that capillary wire has a circle shape and the end of the wire is closed with a button. The

button is open during blood sampling and closed when the head part move upward.

This concept consists of button system, capillary wire, cap, two magnets, external grip cover

and needle. The manual operation of the concept 3 is listed in the following:

The head of the concept moved forward when the blood sampling is done ;

The needled removed;

The cap pressed into the head.

Disadvantages

Risk for blood waste during sampling


Figure 13 Left: The top head of the concept 3. Right: The Button system of the concept 3


20

Advantages

Exact volume


Easy to use

2.2.4 Concept 4 manual sampler with screw solution

This concept is similar to concept 2. The end of the capillary wire can be opening and closing

with using a screw component. The concept 4 consists of screwed bottom head, top cap with

probe-guide surface, O-ring, guide pin, rubber disc, top plug, magnet, capillary wire, external

grip cover and needle include needle shield. A short manual operation of the concept 4 is

listed in the following:

After taking a sample the needled is removed;

Screw the bottom head of the sampler;

The cap pressed into the luer.

Disadvantages

Risk for blood waste during the

transportation process

Bad mixing ability

Figure 14 Concept 4 before sampling. Right: Concept 4 after sampling

Figure 15 The top cap and screwed bottom of the concept 4


21

Advantages

Exact volume

Less assembly part

2.2.5 Concept 5 semi-automatic sampler with ejected needle system

This concept idea is semi-automatic solution with ejected needle system. When the capillary

wire is filling, the bottom head pressed and thereby the needle and the luer part will be

ejected. The concept 5 consists of O-ring, head part with VTC (Vented Tip Cap) interface,

luer part, magnet, capillary wire, external grip cover and needle include needle shield. The

manual operation of the concept 5 is after sampling the bottom head pressed.

Disadvantages

Requires lot of manual operation

Risk for blood waste during the sampling process


Figure 17 The top cap with ejector pin system and bottom cap with snap fit system of the concept 5


22

Advantages

Exact volume


No physical touching of the needle

2.2.6 Concept 6 semi-automatic sampler with two side solution

This concept is two side solutions which the one side has a Vented Tip Cap (VTC) interface

and the other side luer interface. The concept 6 consists of plastic VTC interfaces head, cap,

rubber disc, filter, magnet, capillary wire, external grip cover and needle include needle

shield. A short manual operation of the concept 6 is listed in the following:

Remove the cap of the needle;

Remove the needle by the needle shield;

Twist the luer cap on luer.

Disadvantages

High cost

High blood waste


Figure 19 The top cap with filter system and luer cap of the concept 6


23

Advantages

Exact volume


2.2.7 Concept 7 semi-automatic sampler with luer in the middle

This concept is similar to concept 6, the differences is instill for the luer is placed in the

middle. The concept 7 consists of plastic Vented Tip Cap (VTC) interfaces head, cap, rubber

disc, filter, magnet, capillary wire, external grip cover and needle include needle shield. The

manual operation of the concept 7 is listed in the following:

After taking a sample the needled removed

The cap press on the luer

Advantages

Exact volume

Disadvantages

Bad usability

Bad mixing ability


Figure 21 The filter system and luer cap of the concept 7

Disadvantages

High cost


24

2.3 Morphological analysis

The micro sampler is divided in three cases, one side solution micro sampler, two side

solution micro sampler and middle solution micro sampler. For each case a list of different

design objectives with combination of the solution idea is presented.

2.3.1 Systematically comparing the pairs of objectives

All the design objectives which include technical and economic factors, user requirements,

and safety requirements are systematically compared in pairs, one against the other,

depending on whether the first objective is considered more or less important than the

second, and so on. For example, starting with objective “Risk for blood waste” (RBW) and

work along the table row, asking “Is RBW more important than Price?”... “Than

Manufacturing?”... “Than Usability?”, etc. If RBW is more important than Price, RBW will be

entered into the relevant matrix cell in the table. If RBW and Price are equally important

RBW/Price are entered into the matrix cell and the highest row total indicates the highest

priority objective.

The next step is to assign a numerical value to each objective, representing its weight

compared to the other objectives. A simple way of doing this is to consider the rank-ordered

list as though the objectives are placed in positions of relative importance, or value, on a

scale of 1 to 10

Scale Design Objectives

10 RBW

9

8

7 Mix ability

6

5 Price

4 Usability

3

2 Manufacturing

1 Table 2Assigning relative weightings to the objectives

Risk for blood waste (RBW)

Price Manufacturing Usability Mixing ability Row totals

Risk for blood waste (RBW

RBW RBW RBW RBW 4

Price Price Price Mix ability 2

Manufacturing Usability Mix ability 0

Usability Mix ability 1

Mixing ability 3

Table 1 Rank-order the list of objectives


25

The most important objective, RBW, has been given the value 10 and the others are then

given values relative to this. Thus, objective mix ability is valued as about 70% of the value of

objective RBW; objective usability is valued twice as high as objective manufacturing.

2.3.2 One side solution

The idea with one side solution means that the solution with probe guided interface can only

exist in the luer side. All the solution ideas, to bottom side and luer, are listed in the table

below. They will be weighed from a scale of 1-5 regarding to the most important objective,

Risk of Blood Waste (RBW).

The design solutions which have highest row results (5 and 4) go further to the next pool

“evaluate by design criteria” and the combinations are listed in the following:

A. Filter system Movable silicone rubber with probe guide interface.

B. Button system Movable silicone rubber with probe guide interface.

Filter system

Button system

Screw system

Twist system

Cap Snap fit

Bottom

Row result

5 4 3 3 2 3

Movable silicone rubber with probe guide interface

Fixed plastic part with probe guide interface

and top cap

Eject luer system

Luer

Row result

5 3 2

Table 3 Weighting solution ideas to one side solution


26

2.3.3 The two side solution

The two side solution means that the solution with probe guide interface can only exists in

on the opposite of the luer. All the solution ideas to bottom side and luer are listed in the

table below and weighed from a scale of 1-5 regarding to the most important objective, Risk

of Blood Waste (RBW).

The best combination of the design solutions are listed in the following:

C. Screw luer cap fixed plastic part with probe guide interface, filter and rubber disc.

D. Movable luer system fixed plastic part with probe guide interface, filter and rubber disc.

Cap Movable luer system

Screw cap system to luer

Twist cap system to

luer

Snap fit cap system to

luer Luer

Row result

2 5 4 3 2

Fixed plastic part with probe guide interface, filter and rubber disc

Movable silicone rubber with probe guide

interface

Fixed plastic part with

probe guide interface and

top cap

Bottom

Row result

5 3 2

Table 4 Weightings solution ideas to two side solution


27

2.3.4 Middle side solution

The idea with middle side solution consist in the fact that the luer is fixed in the middle of

the micro sampler and the solution with probe guide interface can be freely placed on the

both side of the micro sampler. All the solution ideas are listed in the table below and

weighed from a scale of 1-5 regarding to the most important objective, Risk of Blood Waste

(RBW).

The design solutions for middle side solution are listed in the following:

E. Fixed plastic part with probe guide interface, filter and rubber disc screw cap system to luer filter system.

F. Fixed plastic part with probe guide interface, filter and rubber disc twist cap system to luer filter system.

Fixed plastic part with probe guide

interface, filter and rubber disc

Movable silicone rubber with probe guide

interface

Fixed plastic part with probe guide interface and top

cap

Top

Row result

5 3 2

Cap Screw cap system to luer

Twist cap system to luer

Snap fit cap system to luer

Luer

Row result

2 5 4 2

Filter system

Screw system

Twist system

Cap Snap fit

Bottom

Row result

5 3 3 2 3

Table 5 Weightings solution ideas to Middle side solution


28

2.4 Evaluate by design criteria

The best chosen design combinations are evaluated from a scale of 1-5 (inadequate, weak, satisfactory, good and excellent) with regard to design criteria as shown in the table below.

2.5 The final concept

The final solution/concept to the micro sampler is concept D which has a slider solution. The idea is that after sampling the luer can slide from one side to the other side which has a probe guide interface. As backup concept, concept A is chosen which has one side solution and consists of filter system and movable plastic part with probe guide interface.

2.5.1 Chosen concept semi-automatic micro sampler with slider solution

The chosen concept idea is semi- automatic solution with easy usability, good mixing ability

and minimum risk for blood waste. The chosen concept has two external parts. One is a top

cover which has a probe guide interface. The second one is a bottom cover which can be used

as grip cover and needle shield. In addition the concept has four inner parts which are bottom

cap with air tunnel interface, filter, mixer wire and a slider which contains of capillary wire,

luer interface and luer cap.

Price Usability Mixing ability

Manufacturing and assembly

Waste of blood

Row totals

Weight scale of design criteria

5 4 7 2 10

Concept A 4 4 5 5 4 121

Concept B 3 4 5 5 4 116

Concept C 2 4 5 4 4 109

Concept D 3 5 5 4 5 128

Concept E 2 2 2 3 4 78

Concept F 3 2 2 5 4 87 Table 6 Evaluate the concept ideas regarding to design criteria.

The slider

Bottom cap

The filter Capillary

wire

Luer

cap

Top

cover

Barcode

Bottom cover

Figure 22 The components of the final concept


29

Furthermore an outline of the using procedure is as following:

a) Remove the cap of the needle;

b) Find the artery and puncture it;

c) Slide the luer back to the other side and lock it by snap fits;

d) Twist the multi-function cover and remove it;

e) Press the luer cap on the luer;

f) Put the micro sampler into the slot of the queue layer.

Luer Needle Mixer wire Needle cover

Figure 23 The inner components and needle system of the final concept

Figure 24 The using produce of the final concept


30

2.6 Prototype of the chosen design concept

A prototype of the chosen concept was present for the users, to obtain feedback from them

in relation to the usability and functionality. Before presentation of the concept, a user

requirement list was prepared in three situations: before sampling, during sampling and

after sampling. Further a simulation of using procedure was performed by the users who

have different educational background. The feedbacks from the users are used to optimize

the chosen concept idea.

A solo evaluation of the chosen concept is performed before it was presented for the users.

The advantages and disadvantages for the chosen concept are listed in the following:

Advantages

Exact volume


Easy to use

Multi-function

Good mixing ability

External grip cover for easy handling

Figure 25 Left: 3D printed bottom over. Right: 3D printed top cover

Figure 26 Left: 3D printed slider. Right: 3D printed sampler with needle and needle cap

Disadvantages

Risk for blood waste during removing the

luer cap


31

2.6.1 Simulation the using procedure of the prototype

The first step of the simulation shows that the prototype holding with all fingers. Afterward it

shown that the user tried to slide the luer of the chosen concept in back position at the same

time, used the right hand to press on the wound.

Then the user slides the luer in back position and was done with press on the wound. The

top cover twisted and the needle was removed. Afterward the luer caps pressed on the luer.

Lastly, the prototype can be put into the slot of the blood gas analyzer.

Figure 27 Left: Simulated blood sampling with all fingers holding. Right: Simulated slide back with one hand

Figure 28 Left: Simulated twist the bottom cover. Right: Simulated press the luer cap on the luer

Figure 29 Left: The bottom cover top put to the slot of the queue layer. Right: The bottom cover top put to single mixer


32

Before sampling

During sampling

After sampling

Before sampling

During sampling

After sampling

2.6.2 User requirements

The requirement lists to the users are divided in two cases which are requirements for the

arterial blood sampling and A-line blood sampling as shown in fig.30 and 31. The goal is that

the user easily can perform the using procedure. Some procedure steps which are difficult to

perform will be notated as a feedback to improve the design.

The user must open

the packaging

The user must

remove the needle

cover

The user must

find the artery and

puncture it

The user must easily

slide the luer back

The user must understand

the twist system

The user must press the luer

cap on the luer

The user must set the micro

correct into the mixer slot of

the queue layer

Dispose the parts

Figure 30 User requirements to arterial blood sampling

The user must open

the packaging

The user must

remove the needle

cover

The user should slide

back

The user must

understand the twist

system

Dispose the parts

The user must

put the luer into

the A-line

The user must press

the luer cap on the

luer.

The user must set

the micro sampler

correct into the

mixer slot of the

queue layer

Figure 31 User requirements to A-line


33

2.6.3 User team

The user team was consisting of Radiometer employees who have different background such

as engineer and technician (see fig 32.). The team´s members have tried to slide the slider

back and forward, twisted the middle cover and simulated to take a blood sample with

holding on the prototype in different angles. Jesper and Rikke have many years’ experiences

using syringes and blood sampling, so their feedback was only based on usability. Torben and

Teit have good experience designing samplers. Their feedback was very wide and coved both

usability and functionality. Furthermore many mechanical and design students from

Radiometer were also involved in giving feedback.

Name: Jesper Kristiansen

Title: Medical laboratory technician

Company: Radiometer A/S

Name:Torben Haugaard Jensen

Title: R&D Engineer


Name:Rikke Rune Petersen

Title: Biomedical laboratory technician


Name:Teit Anton Nielsen

Title:: R&D Engineer

Company: Radiometer A/S Figure 32 List of participants


34

2.6.4 Feedback from the users

Lot of feedback to the prototype linked to usability and functionality was received. The

feedback is listed in the following:

Improve feedbacks:

Avoid slider/slide system or minimize the slide way – It is difficult to slide back with

one hand. Radiometer has a lot of problems with current needle shields which are

based on a slide system solution.

Press and slide – It is difficult for the user to press and slide at the same time while

they wear rubber gloves.

Better grip area on the slide – It is difficult for the user to grip the slider.

External diameter of the slider – It is difficult to slide back with all fingers holding

because the external diameters of the slider touch the fingers.

The shape of the slider- It is difficult for the user to understand twist system, there is

a risk for twists the opposite way and destroyed the micro sampler.

Mixing ability – Ensure that the mixer wire can be moved in manual and automatic

situation.

Positive feedback:

Easy to dispose.

All parts are on the micro sampler - Not use time to find any subparts.

Easy to handle.

Same sampling technique - Don’t need to change your sampling technique.

Needle is completely visible.

Possible to see the blood inside.


35

2.7 Version 2 of the concept

Based on these feedbacks from the user team, the design to the chosen concept is improved.

The slider has lots of improve feedbacks therefore it is handled as first step. Since it was

almost impossible to use the chosen concept with one hand and it was difficult to slide back

and forward during a stressed situation, the slide system is changed. So instead of sliding the

luer back and forward, the needle shield (bottom cover) can be slides to one side and back

again. In this way the needle cover is not necessary to use (see figure below.)

Furthermore, the capillary wire with luer interface and luer cap is set in to the top cover and

thereby the slider part is removed. In addition, the dimension of the rubber cap is increased,

so it can be pressed into the end of the top cover, and it has more surface area to the probe

of the blood gas analysis to pass.

Figure 34 Top: Top cover. Bottom: Cross section of top cover

Figure 33 Left: Bottom cover closed. Right: Bottom cover slide to open position


36

2.8 Prototype of design concept version 2

The final concept was been updated and a new 3D printed prototype was realized to obtain

feedback again from the user team with regard to usability and functionality.

2.8.1 Simulate the producer of the prototype

The simulation shows that the prototype can be hold with all fingers and pen-like holding.

Afterward the twist system and removing the needle are simulated (fig. 38 left and middle).

Lastly the prototype is put into the mixer slot of the queue layer (fig. 38 right).

Figure 35 Left: 3D printed Top cover. Right: 3D printed bottom cover

Figure 36 Left: Top cover with insert needle. Right: 3D printed version 2 of final concept

Figure 37 Left: Version 2 final concept holding with all fingers. Right: Simulated sampling holding as pen


37

2.8.2 Feedback from the user team to version 2

Again the new version of the prototype is presented for the user team to obtain feedback

with regard to usability and functionally. All the feedbacks are listed in the following:

Improve feedbacks:

Less grip area during sampling.

Positive feedback:

Much simple to use compared with the first version.

Less parts to depose.

Easy to understand the operation steps.

Cheaper than the first version.

Better to assembly compared to the first version.

More friendly to one hand handling.

Figure 38 Left: Simulated the twist system. Middle: Top cover after twisted. Right: Top cover put into the slot of queue layer


38

2.8.3 Mixing test

A simple experiment test is performed to prove that the mixer pin can be moved by the

Radiometer magnet and the automatic mixer slot. A capillary wire is cut through to a length

of 49.6 mm which is the same length as the prototype. Furthermore the mixer wire is put in

to the cut capillary wire. The ends of the capillary wire are closed with two caps. Lastly the

capillary wire is pressed into a syringe which has same external diameter as the prototype.

The test is performed for manual and automatic mixing, first without any liquid afterward

with a liquid which has same viscosity as adult blood.

Figure 39 Left: Capillary wire with insert mixing wire. Right: The syringe with insert capillary wire and Radiometer magnet

Figure 40 Left: The syringe insert to the single mixer slot. Right: The syringe insert to the single mixer slot with liquid


39

2.9 Comparison of the samplers

Based on the requirements to micro sampler (see chapter 1) the chosen concept must be

more user-friendly than a 1 ml sampler. Therefore first version and second version of the 3D

printed prototype are compared with the using procedure of 1 ml sampler from Radiometer.

Version 1 Version 2 1 mL sampler

Remove the cap of the needle

Slide the bottom cover to side

Remove the cap of the needle

Find the artery and puncture it



Slide the luer back to the other side and lock it by snap fits

Slide the bottom cover back

Slide needle shield forward and lock it by snap fits

Twist the multi-function cover and remove

Twist the bottom cover and remove

Pull the needle shield off

Press the luer cap on the luer

Press the luer cap on the luer

Find the Vented Tipcap (VTC) and press on the Luer

Put the sampler into the mixer slot of the queue layer


Vent the sampler

Dispose the needle shield and the cap of the needle

Dispose the bottom cover needle shield


- - Dispose the needle shield and the cap of the needle

Table 7 Comparison table of chosen concept and 1mL sampler from Radiometer.

2.10 Conclusion

The concept is very well optimized and the problems and worries the user team had

concerning usability and mixing ability were solved. Furthermore the chosen concept has

been simplified. It’s not necessary to use two components (the slider and the needle cover).

In addition the user team feels that the concept product is very easy to use and they can

easily understand the operation steps. The experiment mixing test proved that the mixer pin

can be moved by the Radiometer magnet and the automatic mixer slot. Lastly, the concept

has less operation steps than the existing 1 ml Radiometer sampler.


40

3. Material selection In this chapter the thermoplastic materials for the micro sampler are selected systematically in a 5 step method, which are listed in the following:

First step - Establishment of demands of planned use. Second step - Translation of demands for the parts into demands for the materials.

Third step – Divide the demands to material in three categories.

Four step – Elimination of materials.

Few step – Select the final material, in the most convenient and cost effective way.

3.1 Loadings analyzing to the sampler

To achieve the best material selection, the micro sampler is analyzed for loading. Three situations of loading are listed in the following:

The loading situation during sampling – The only load the micro sampler is exposed of at normal use is during the sampling but since the load is very small during the sampling, the resulting stress is negligible. It must also be considered that even though load from sampling is small, the material is exposed to bigger stresses due to inappropriate use and stresses applied assembly of the parts.

During unavoidable mishaps as fall from hand –The sampler is expected to be exposed to falls when handling the micro sampler. The sampler might also experience crashes, but this is an extreme situation, and therefore it will not be considered in the choice of materials.

During transports the sampler – The sampler is expected to be exposed compression by app 3 kg (compression under boxes in the container )

Calculations of the three situations of loading will be performed in next chapter “design and calculations”

3.2 Material selection bottom cover

The first step is to list all the product demands for the bottom cover in table 8.

Product demands

Manufacturing Process Must be injection molding because of the complex geometry.

Color Transparent

Surface Outside: Glossy. Inside: Mat. The outside of the bottom cover has to appear of good quality, but inside the surface needs more friction to improve the assembly.

Features

Core out to avoid sink marks.

Snap fit – two snap fits to assembly the


41

parts with bottom multi cover and the slider.

Text – embossed text to show the cavity and tool number.

Environment

UV resistant, the micro sampler must not change appearance, though it is left on the window frame in sunlight during the day

Temperature resistent from -5 to 40

Chemically resistant Must be able to sterilize therefore it must be resistant for Ethylene Oxide.

Labeling with Radiometer Medical ApS’ logo and colors, therefore it must be resistant to glue.

Table 8 Product demands bottom cover.

The next step is translation of demands for the parts into demands for the materials and further divided them in three categories.

Category Demands for part Demands for material

Category 1 (qualitative material properties , who cannot be given a value)

Injection molding Injection molding

Color Bright colors

Features Snap connection

Surface Ability to achieve mat surface

Environment UV resistant Low temperature resistant

Chemically resistant Ethylene Oxide resistant Glue resistant

Category 2 (quantitative material properties, that are not directly dependent of material thickness)

During unavoidable mishaps as fall from hand

High impact strength

During transports the sampler

High Young’s modulus

Low cost of final product Price compared to stiffness must be as low as possible

Category 3 (quantitative material properties )

- -

Table 9 Material demands divided in three categories to bottom cover.


42

Amorphous thermoplastic materials Semi crystallite thermoplastic materials

Demand PS ABS SB/SAN PVC PMMA PPO/PS PC PE PP POM PA PBTP PTFE

Injection molding

Transparent Bright colors Snap connection

Impact strength

UV resistant Glossy surface

Temperature 5 to 40

Ethanol at 20

Passed all demands

Many possibilities for suitable materials are achieved. For a good snap-fits connection it is

suitable with a material which has a low difference in relaxation modulus over time. Here PP

(polypropylene) is a very good choice since it’s able to maintain, it modulus for long time and

it has good ethanol resistant to fulfill the sterile treatment. Furthermore the elasticity allows

micro sampler to be flexible (not extreme brittle), so it can be compressed by app. 3 kg

during transportation. I addition to this PP is quite cheap and has a good impact strength to

protect the micro sampler. The disadvantage is that PP has a high shrinkage but since the

parts have not tight tolerances, it is acceptable.

Creep modulus 23°C (Short upper 10000h lower)

3400 2300

2300 930

3600 1300

3400 1400

3300 1900

8700 6800

2200 1300

1000 200

1250 350

3000 950

1300 380

2600 770

-

Young’s Modulus [GPa]

1.2-2.6 1.1-2.9 3.5-3.8 2.14-4.14

2.24-3.8

2.2-2.6 2-2.44 0.62-0.896

1.5-2 2.5-5

2.6-3.2 1.6-2 1.46

Price due to stiffness

1.15 2.62 1.48 1.51 2.25 3.74 4.97 1.29 1 3.80 4.49 3.91 -

Materiel PS ABS SB/ SAN

PVC PMMA PPO/ PS

PC PE PP POM

PA PBTP PTFE

Table 10 Evaluated thermoplastic materials regarding to material demands to bottom cover

Explanation Very good

Good Bad Not good


43

As backup materials transparent ABS (Acrylonitrile butadiene styrene) and SAN (Styrene-

acrylonitrile) have been chosen, because they fulfill the material demands very well and they

have a good property to snap fit connections. Furthermore these materials have a cheap

price compered to stiffness.

3.3 Material selection for top cover

In this section the materials for top cover which included capillary wire and luer cap are selected. As first step the product demands are listed in table 11.

Product demands for the slider

Manufacturing Process Must be injection molding because of the complex geometry. The top cover must be molded from virgin material.

Color Transparent but must the coloring to dim the light from the blood gas analyzer 50 %

Surface Outside: Glossy. Inside: Matt. The outside of the top cover has to appear of good quality, but inside surface needs more friction to improve the assembly. Moreover, surface tension of the capillary wire must be higher than surface tension of blood, for the capillary wire can be able to draw blood samples from patients.

Features

Core out for unless sink marks

Snap fit – two snap fit to assembly the parts with bottom cover and top cover.

Press fit- luer cap press on the luer.

Ribs – avoid sink marks, less material and provide bending.

Text – embossed text to show cavity and tool number.

Environment

UV resistant, the micro sampler must not change appearance, if it is left on the window frame in sunlight during the day.

Temperature resistent from -5 to 40

Chemically resistant Should be able to sterile therefore it must be resistant for Ethylene Oxide.

Should contain heparin therefore it must be resistant for heparin.

Permeability Oxygen permeability coefficient must be low, so the blood must change the pO2 of the sample less than 2% during storage duration of 30 min.

Table 11 Product demands to the top cover


44

The next are translation of demands for the top cover into demands for the materials and further divide them in categories.

Category Demands for part Demands for material

Category 1 (qualitative material properties , who cannot be given a value)

Injection molding Injection molding

Color Bright colors

Features Snap connection Press fit Ribs

Surface Ability to achieve mat surface. Surface treatment (corona or plasma treatment) for get higher contact angle and thereby high surface tension than blood.

Environment UV resistant Low temperature resistant

Chemically resistant Ethylene Oxide resistant Heparin resistant

Permeability Low oxygen permeability coefficient

Category 2 (quantitative material properties, that are not directly dependent of material thickness)

During unavoidable mishaps as fall from hand

High impact strength

During transports the sampler

High Young’s modulus

Low cost of final product Price compered to stiffness must be as low as possible

Category 3 (quantitative material properties )

- -

Table 12 Material demands divided in three categories to the top cover.


45

Amorphous thermoplastic materials Semi crystallite thermoplastic materials

Demands PS ABS SB /SAN

PVC PMMA PPO/PS PC COC PEN PETG PE PP POM PA PBTP PETP

PTFE

Injection molding

Transparent Bright colors Snap connection

Impact strength

UV resistant Glossy surface

Temperature 5 to 40

Ethanol at 20

Permeability

Surface tension

Corona or plasma treatment

Passed all demands

The permeability of oxygen and surface tension are weighed very high. Because permeability

has big influence on the test analysis and the surface tension has influence on functionally of

Creep modulus 23°C (Short upper 10000h lower)

3400 2300

2300 930

3600 1300

3400 1400

3300 1900

8700 6800

2200 1300

3000 2400

- 3100 1900

1000 200

1250 350

3000 950

1300 380

2600 770

-

Young’s Modulus [GPa]

1.2-2.6

1.1-2.9

3.5-3.8 2.14-4.14

2.24-3.8 2.2-2.6

2-2.44

2.2-2.6

2-2.5 2-2.4 0,62-0,896

1.5-2 2.5-5 2.6-3.2

1.6-2 1.46

Price due to stiffness

1.15 2.62 1.48 1.51 2.25 3,74 4,97 - - - 1.29 1 3.80 4.49 3.91 -

Materiel PS ABS SB/SAN PVC PMMA PPO/ PS

PC COC PEN PETG PE PP POM PA PBTP PTFE

Table 13 Evaluated thermoplastic materials regarding to material demands to the top cover

Explanation Very good

Good Bad Not good


46

600

400

120

40 12

40 41 39 38 35

0

100

200

300

400

500

600

700

COC PETG PVC (rigid) PA 6 PEN

Pe

rme

abili

ty [

cm3 /

m2*d

*bar

] su

rfac

e t

en

sio

n [

mN

/m]

Polymer Materials

Permeability of oxygen

Surface tension

capillary wire. Therefore all the materials which are suitable for the slider are further

compared regarding these material criteria (see fig.41).

Since rigid PVC has additives which are harmful to health and PA 6 has very high water

uptake which can change the dimensions stability in stiffness, these are neglected.

PEN is thermoplastic polyester as PET (Polyethylene terephthalate) but PEN has even better

barrier properties than PET. Since the material provides a very good oxygen barrier, it is

particularly well-suited for bottling beverages that are susceptible to oxidation, such as beer

e.g. green Carlsberg bottles. In addition, PEN has a better thermal, mechanical and

chemically properties than PET. Because the material is four times more expensive than PET,

the material cannot be chosen as final material, but only as backup material.

The second chosen backup material is COC especially Topas 8007 which has a very low water

vapour permeability, high transparency, extremely low water absorption, high rigidity,

strength and hardness. Furthermore the material has excellent biocompatibility and blood

compatibility (Hemolysis), which is carried out according to guidelines given in the FDA (U S

Food and Drug Administration), Blue Book memorandum, and by the International

Organization for Standardization (ISO -10993). Lastly the material has a very good melt flow

ability which is an extra benefit, since the capillary wire as included in luer cap has a long

flow length. The disadvantages are that the material is expensive and it´s has a highest

permeability coefficient of the compared materials.

Finally, the best suitable material to the top cover can be chose as PETG (Glycol modified

Polyethylene terephthalate) because it has a low permeability coefficient of oxygen and it’s

fulfill all the other material demands. PETG is a copolymer of cyclohexane dimethanol with

ethylene glycol and tereohthalic acid. PETG is characterized by a high stiffness and hardness

Chart 1. Figure 41 Permeability of oxygen and surface tension to the suitable materials

http://en.wikipedia.org/wiki/Polyethylene_terephthalate

http://en.wikipedia.org/wiki/Beer


47

and good toughness which could be benefits to carry load. Furthermore the PETG can be

sterilizable by both ethylene oxide and gamma radiation.

The advantage is that current Radiometer capillary wire is made of PETG and the material

can already fulfill all the user requirement test and stability test. The disadvantage could be

the high hardness of PETG, since it could be a problem for press fit (luer cap press on the luer

interface of the capillary wire).

In addition since the thermoplastic materials have a low surface tension as compared with

glass, it must have a corona or plasma treatment to be able to draw blood sample from

patients.

3.4 Further work for PETG

Since PETG is not often used in mechanical application e.g. for snap fit and press fit, the yield

strain of the PETG is compared with other thermoplastic materials (see fig. 42). The chosen

manufacture for PETG is Easter GN002 which is one of the most common types used for

injection molding.

Figure 42 Yield strain of PETG compared with other thermoplastic materials

PETG has a bad performance to snap and press fit but since the micro sampler is disposable,

it is considered acceptable.

4,2

9,3

5,6

2,2 1,4

12

5

7

0

2

4

6

8

10

12

14

PETG POM PC ABS PS PP PMMA PTFE

Yie

ld s

trai

n

Thermoplastic


48

3.5 Material selection for the filter, rubber caps and mixer pin

Filter, rubber cap and mixer pin buyers from Radiometer Medical ApS suppliers. The

demands to the parts are listed in the following:

Filter:

The filter must be hybrid.

The filter must vent an air bubbles.

When the filter is filled with blood, it must be closed.

Rubber cap:

The rubber cap must be silicone rubber.

Although the cap is cut through, it must seal during sampling.

Rubber cap must have natural coloring.

Mixer wire:

The mixer wire must be magnetic.

The mixer wire must have good dimension stability during sampling.

The diameter and lengths of the mixer wire must have very tight tolerances.

3.6 Summary and conclusion

The chosen material to the bottom cover is PP, because it’s quite cheap material, with low

creep modulus which is good to snap fit connection. Moreover the PP is flexible which can

allow compression during translation. Lastly PP has good impact strength to protect the

micro sampler.

The next chosen material to the top cover which included the luer cap and the capillary wire

is PETG. PETG fulfills all material demands and it’s has a good oxygen barrier property which

is very important material criteria for the micro sampler. But since the thermoplastic

materials have a low surface tension compare with glass, it must have a corona or plasma

treatment to be able to draw blood samples from the patients.


49

4. Calculations and dimensioning This chapter describes design, process, mechanical and cost calculation for the micro

sampler. As first step the design is improved by using ribs, draft angles and minimized the

undercuts. Moreover, the dimension of snap fits, capillary wire, integral hinges and press fits

are found by design calculations. Accordingly, the process data of cooling time, packing time,

pressure drop etc. are calculated for the molded parts of the micro sampler. In addition, the

production cost for the micro sampler is analyzed and calculated. Lastly, the maximum

values of reaction force, torque and angles are found for inappropriate use by mechanical

simulation and calculation.

4.1 Design improvement and calculation

The wall thickness of the molded parts is kept to a minimum and the stiffness of that is

improved with ribs. The wall thickness is tried be kept equal to prevent warpage and the

undercuts is kept to minimum, to reduce high tool costs. Furthermore molded parts are

designed with a draft angle of 1.5⁰. In addition, it is ensure that molded parts follow the

moving part when the mold opens. Lastly sharp corners, notches and edges are avoided (see

the improved parts picture in fig. 43 and fig. 44).

Figure 43 Top: The cross section of top cover. Bottom: Cross section of improved top cover


50

The Integral hinges of the bottom cover is improved by a spring functions shown in fig 44

(bottom). For the head of the bottom cover can easily slide to side and back again. It is

especially necessary during a stress situation where the nurse prefers single hand use of the

micro sampler.

Figure 44 Top: The cross section of bottom cover. Bottom: Cross section of improved bottom cover


51

4.1.1 Press fit calculation for the luer cap

The luer geometry is assumed as truncated cone geometry. The surface area is calculated

from the formula below where s is the slant height of the truncated cone, r is the top radius

and R is the bottom radius of truncated cone.

Furthermore, the desired maximum force in axial direction is calculated a maximum load

assuming press on the luer (PL) of 3 kg.

The specific pressure between the luer interface of the capillary wire and luer cap is

calculated from the formula below, where the friction coefficient µPETG is found to 0.2 from

the datasheet of PETG.

Moreover, the stresses in x and y are calculated for end of the luer cap (bottom side).The

luer cap is as assumed as a thin walled tube.

Lastly, the safety factor against break is calculated from the formula below where is the

stress at break and is the reference stress.

√

Figure 46 Sketch of luer cap

Figure 45 Sketch of truncated core


52

4.1.2 Snap fits calculation

As a first step, the strain level in the straight and deflection force of beam are calculated.

From the ratio between start high and end high of the snap fit, the factor for the cantilever

beam are found to K=1.863. Accordingly, the strain level in the straight beam is calculated,

where Y is deflection of a straight beam end, L is the length of the straight beam.

Finally, the deflection force of beam calculated, where B is the width of the straight beam, E

is tensile modules for PP.

4.1.3 Integral hinge calculation

The length and radius of the integral hinge for top and bottom cover are calculated by the

formula below. Where s is the thickness of the integral hinge, is the bent angle, is the

strain amplitude in % and is the safety factor as assumed to 2.

The calculated length and radius of the integral hinge for top and bottom cover are collected

in table 14. The top cover is assumed to withstand at least 104 load cycles in which it is bent

by an angle of 180⁰.

Top cover Bottom cover

Length [mm] 2 1.57

Radius [mm] 0.63 0.5

Thickness [mm] 0.25 0.3

Table 14 Dimension of integral hinge

Figure 47 Sketch of integral hinge


53

4.1.4 Length calculation of capillary wire

The length of capillary wire had calculated from the formula below which total volume is the

sum of target volume, production tolerance volume, the mixer wire volume and filter

volume, and r is the inner radius of capillary wire.

4.1.5 Diffusion calculation of the capillary sampler

Since the amount of oxygen (pO2) and carbon dioxide (Co2) are important to obtain a correct

test analysis. The diffusion amount of pO2 and Co2 are calculated during storage duration of

30 min. The steady state formula is used (se formula below) where Pc is the permeability

coefficient of the plastic material, A is the surface area, Pout is the outer pressure which is 21

% of the atmosphere pressure for oxygen and zero for Carbon dioxide and Pin is the inner

pressure which is the partial pressure of adult blood. The partial pressure is set to 14.4 kPa

for oxygen and 6 kPa for Carbon dioxide according to Danish chemical compendium (Henrik

Olesen , Kemisk kompendium).

Figure 48 Left: Integral hinge of bottom cover in open position. Right: Integral hinge of bottom cover in closed position

Figure 49 Left: Integral hinge of top cover in open position. Right: Integral hinge of the top cover in closed position


54

The calculated volume change of pO2 and Co2 are collected in table 15. The volume change of

CO2 is negative because the outer pressure is zero and the diffusion occurs inside.

The requirement of the pO2and CO2 only allows max 2% volume change. The volume change

of CO2 is accepted but the volume change of O2 is critical because it is next to 2 %. The

highest volume change is for capillary wire because the capillary has a highest surface area.

The surface area cannot be lower because lower surface area will give higher diameter and

higher diameter may cause a risk for air bubbles.

4.1.6 Surface tension calculation

A simple model of the capillary pressure in a gas/blood is shown in fig. 50. The model is used

to calculate the necessary surface tension for the capillary to be fulfilled with blood during

sampling. The surface tension is calculated from the formula below where R is the inner

surface of the capillary wire, g is the acceleration due to gravity, and densities

of blood and air, h is height of blood level and cos( is the contact angles of blood.

Volume Change of pO2 [%] Volume Change of Co2 [%]

Capillary wire 1.34 -0.58

Rubber caps PVDF coating 0.0028 -1.3E-5

Filter free air gab 0.23 -0.098

Filter, rubber and PETG 0.028 -0.011

Sum 1.60 -0.69

Table 15 The calculated volume change of pO2 and CO2

Figure 50 Capillary pressure in a gas/blood system


55

However, it’s only necessary to surface treat the capillary wire, so it’s half the calculated

value 96.64 mN/m. Because the blood pressure from the model is less than the blood

pressure in the arterial blood veins.

4.2 Injection molding Process calculation

In this section the calculations relation to injection molding process are performed.

4.2.1 Ram position calculation

The ram position of the top and bottom cover is calculated. The specific volume of the top cover is calculated from formula below. Where r is radius of the rotation screw, is coefficient of linear thermal expansion, is the density and is the difference temperature. Furthermore the volume position ( ) was calculated to 3.34 mm for

screw a diameter ( ) of Ø30 mm. But the screw diameter which has Ø18 mm has been chosen because it gives a shorter retention time in the cylinder.

Moreover, part weight is calculated where W is the part weight and V is the volume of the

part.

Ram position of volume is calculated by divided the part weight with the specific volume.

The sum of the suck back position (SB), residues cushion (Rsp) and Ram position of volume

( ) give the ram position. SB is set to 6 mm and Rsp is set 10 mm to ensure that there is

enough cushion melt during the packing pressure and packing time series.

Furthermore, the specific volume, part weight and ram position of volume are also

calculated for bottom cover. The suck back position and residues cushion are set as top

cover.


56

4.2.2 Cooling time calculation

The cooling time calculations for top and bottom cover are performed. The cooling time for

top cover is calculated for the thickest thickness. First the criterion for using the cooling time

formula is calculated. Where is the heat deflection temperature for the materials, is

the initial melt temperature and is the initial mold temperature.

When the criterion for the cooling time formula is fulfill. The cooling time for the thickest thickness is calculated where B is half of the chosen thickness, is the effective thermal

diffusivity, k is the coefficient of thermal conductivity, CP is the Specific Heat Capacity and is the density.

(

)

Furthermore, the cooling time for the bottom cover is calculated. Again the criterion is

calculated.

Then the criterion is fulfilled, and the cooling time for the most critical area is calculated

from the formula below.

(

)

4.2.3 The packing time calculation

As first step the gate diameter of the parts are chosen. To choose the cavity gate diameter for the top cover, the fig.51 is used as guideline. The cavity gate diameter is found to Ø 1.15 mm.


57

Figure 51 Graph to find cavity gate diameter (Synventive hot runner guide)

After the cavity gate diameter is found, the packing time is calculated from the formula

below. Where is radius of cavity gate diameter and is the glass transition temperature.

(

)

Because the shot weight of the bottom cover is lower than 1 g, the guide line graph cannot

be used. Therefore the cavity gate diameter is chose according to “Runner and Gating Design

Handbook by Jonh P. Beaumont”, which describes that the gate diameter can be estimated

to 70 % of the well thickness.

Accordingly, the packing time for the bottom cover is calculated.

(

)


58

4.2.4 Pressure drop calculation

The pressure drop for the bottom and top cover are calculated. To calculate the top cover

that is divided into two sections one is the external layer of the top cover and the second

one is the capillary wire. Sum of the two sections gives the total pressure drop of top cover.

The head and cap of the top cover is neglected. The pressure of the external layer is

assumed as pressure drop between two plates. As a first step the shear rate is calculated

from formula below. Where Q is the injection rate, s is the thickness and W is the width.

The next step is to found the parameters in the power-law model. The parameters found

from the PETG GN 002 viscosity graph at a melt temperature about 260 C. The reading point

is ( ; ) and ( ; ). Afterward the reading point insert

in the power low model and the parameters in the power-law model are found.

And that gives

Accordingly, the pressure drop for the external layer (section 1) is calculated.

( (

)

)

Figure 52 Viscosity graph of PETG


59

Furthermore, the shear rate and the pressure drop for the second section (capillary wire) is

calculated, in the same way. The shear rate for the section 2 is calculated to

from formula below. Afterward reading points from viscosity graph are found to

( ; ) and ( ; )

And that gives

Accordingly, the pressure drop for the section 2 is calculated.

( (

)

)

Finally, sum of the pressure drop for the top cover calculated.

Furthermore, the pressure drop for the bottom cover is also calculated. To do that the part is

dived into three sections where one is the bottom side, the second one is the clips area and

the last one is the top side which has conically shape. The three sections are assumed as

pressure drop between two plates and the calculation methods is same as pressure drop

calculation of top cover.

Figure 53 Viscosity graph of PP


60

4.2.5 Clamp force, fill time and packing pressure calculation

The packing pressure is assumed as 80 % of the total pressure drop both for top and bottom

cover.

The clamp force for the parts calculated:

Based on these calculations the injection molding machine (machine) is chosen. The chosen

machine for the two parts is an Engel ES 80/25 HL-VICTORY which has screw diameter of Ø18

mm, max clamp force 250 kN and maximum injection rate 41 cm3/s (see technical data of the

machine in the appendix A).

Lastly, the fill time of the top and bottom cover are calculated from formula below, where Q

is set as the maximum injection rate of the machine and V is the volume of the parts.

4.2.6 Cycle time calculation

The opening and closing time is set to 1.4 s which is the dry cycle (trockenlauf) of the

injection molding machine and the robot time/break time is assumed to 1 s.

Cycle time of top cover:

Cycle time of bottom cover:


61

4.3 Cost calculation and mold design specification

This section describes the cost calculation and mold design specifications of the parts. The

cavities number of the mold and production cost are calculated. During the mold design

specifications, all the demands to the tool maker are listed to obtain the best mold design.

4.3.1 Cavity number calculation

The first cavity number calculation is calculated for top cover. The mold is expected to

produce 2,5 million (m) shots during 5 years. There are two factors which have big influence

on choosing the cavity number. One is the machine price during the production and the

second one is mold price. The two factors will be plotted in same graph and the intersection

of them gives the best cavity number.

The machine cost will be plotted from formula below, where Ep is the expected parts during

5 year, CN is the cavity number, tC is the cycle time and MP is the machine price which is

assumed as 250 kr/h.

( )

( )

The mold cost information has been obtained from SV (Sønderborg Værktøjsfabrik) , for one

cavity mold it will cost 600.000 kr. and for 8 cavities it will cost 2.025 mkr. Every time, the

cavity number doubles, the mold cost price will be multiplied by 1.5 and it can be described

from the function below:

Where a can determined by log:

And, finally the function of mold cost describes:

The machine cost and mold cost are plotted in figure 54 as function of cavities number. The

intersection for the two plots is 3 and it gives the lowest total cost (machine cost +mold

cost). But since the mold cannot be chosen to 3 cavities, it is chosen to 4 cavities which is the

next lowest total cost after 3 cavities please see fig 55.


62

Figure 54 Cost for top cover plotted as function of cavity number

As seen from fig.55. The total cost is lowest at 3 and 4 cavities and thereby it increases with proportional with cavity number.

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Co

st [

kr]

Cavity number

Machine price

Tool price

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Tota

l co

st

Cavity number

Figure 55 Total cost of mold and machine plotted as function of cavity number


63

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

The cavity calculation for the bottom is calculated in same way as cavity calculation of top

cover.

(

)

(

)

The mold cost of bottom cover is approximated the same as top cover:

Figure 56 Cost for bottom cover plotted as function of cavity number

The intersection for the two plots is 3 but the mold is chosen to 2 cavities because the wish

to fill all cavities at the same time and further the lower cost after 3 cavities is 2 cavities (see

fig.57).

0

500000

1000000

1500000

2000000

2500000

3000000

3500000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Co

st [

Kr]

Cavity number

Machine price

Tool price

Figure 57 Total cost of mold and machine plotted as function of cavity number


64

4.3.2 Productions cost

A detailed calculation of other parts (such as needle, rubber cap and filter etc.) to the micro sampler is neglected during this calculation. The only one detailed calculation is for top and bottom cover. As first step the injection molding machine’s cost is calculated. Relation to the size of the machine the machine price is assumed to250 kr/h. The machine price included the utility bill and rental of the injection molding machine.

((

)

(

)

)

The next cost calculation is the material cost, the material waste is assumed to 2 % during the production for both parts.

(

)

As mentioned before, the mold of the top cover is chose 4 cavities and the mold of the bottom cover is chosen as 2 cavities.

In addition, it is assumed that the production is running nonstop in 5 years and that the tool daily maintenance is carried out by authorized employees. The time authorized employees use on the machine is assumed to be 4 hours and their hourly pay to 170 kr/h.

Lastly, it is assumed that the mold will be sent to maintenance every 12-month. The transport, control of the mold, O-ring shift and the authorized employees cost is assumed to 50.000 kr.

And, the total fixed costs can be calculated.

Further, it is assumed that the average cost (AVC) of the needle, rubber cap, mixing wire and filter is 2 kr. per micro sampler. Based on that the total cost function as quantity of the micro sampler (Q) is described as:

In addition, there is an informed from marketing of Radiometer Medical ApS that the micro sampler sales cost will be about 1 dollar which is equal to 5,63 kr. So, the total revenue function as Q can be described as:


65

The two functions are plotted in fig 58. The area where TR is lower than TC is defined as “loss areas” and the areas where TR is higher than TC are defined as “profit areas”. The intersection of the two functions gives the breakeven volume. And it can be calculated when TC =TR.

⇒

⇒

Since, the profit areas are bigger than loss areas, it can be concluded the investment is optimal.

4.4 Mold design specification The mold of the top and bottom cover will be specified in this section by design of cavities,

gate and specification demands to the tool maker.

4.4.1 Mold cavities design

The mold cavity design for top cover is shown in fig.59. The idea is that inner cores move in x

direction and the mold opening and closing way is in z direction.

0

2000000

4000000

6000000

8000000

10000000

12000000

14000000

16000000

0 500000 1000000 1500000 2000000 2500000 3000000

Kr

Q

TR

TC

Figure 58 Total cost (TC) and Total revenue (TR) plotted function as quantity of sampler (Q)

Figure 59 Mold cavity design of top cover


66

Figure 60 Mold cavity design for bottom cover

Furthermore, the cavity mold design for the bottom cover is shown in fig 60. The inner cores

move in x direction and the mold opening and closing in z direction.

4.4.2 Mold gate design

The mold gates of the top and bottom cover are designed with a hot runner from the Synventive molding solution. Since the parts have a complex geometry and they are very difficult to fill, especially top cover, direct gating on the cavities by using one nozzle per cavities is chosen (see figure 61). Furthermore, this gating type has a manifold system to hold the plastic hot during the cycle time. Advantages and disadvantages of the hot runner system compared with cold runner system are listed in the following: Advantages

Direct gating on the part.

Less material waste.

No pressure drops on the inlet/sprue.

More controlled molded part.

Better welding line weld.

Disadvantages

Expensive.

Can gives problem with heat-sensitive materials e.g. PVC.

Difficulty to clean the manifold system.


67

4.4.3 Mold specification

The purpose of this specification is to define the conditions given by Radiometer Medical ApS

(Radiometer) wishes are fulfilled for top and bottom molds/tools. The general specifications

of the molds are list in the following:

Bolts in metric standards DIN 912, quality 12, 9.

The mold must consist of standard mold plates, guide pins and bushings (European standards, e.g. HASCO parts).

Mold base made of stainless steel (eg.1.2085 or 1.2099).

Mold has to be guided by guide elements as Hasco Z18 (Z19), besides the normal guide pins.

The mold must be designed with replaceable and interchangeable inserts for each cavity. The inserts must be designed so that they are impossible to assemble incorrectly.

The mold must be designed with stripper ring for ejection of the part.

Spark eroded parts to be tempered immediately after processing, according to steel specifications.

All outer corners and edges on the mold must be chamfered 2 × 45.

Ejection interface with Injection Molding Machine in the centre of the mold.

The mold must be able to produce in full automatic mode on the Injection Molding Machine.

Ejection must be without any help from air pressure.

The Water connections are to be marked individual e.g. 1 IN – 1 OUT; 2 IN – 2 OUT; etc. the Figures height must be minimum 6 mm.

All surfaces must be made according to the specified surface type and surface roughness according to the GPS-drawing.

The molds must be manufactured to operate without use of release agents. It is allowed that movable parts are lubricated with a lubrication approved for food and drugs. Only a limited but adequate amount of lubrication should be used.

Figure 61 E.g. of Multi cavity mold with manifold system (Synventive molding solution)


68

At wearing surfaces, lubrication free surfaces with low wearing and low friction should mainly be used.

It must be ensured that no lubrication enters the cavities.

The mold must be mounted with bridge with thread for eyebolt for transportation purposes.

Both eyebolt and screws must be adequately dimensioned for the handling of the mold.

The eyebolt must be placed vertically above the Centre of gravity of the mold.

The placement and dimensions of the cavity marking must set according to GPS drawing.

Furthermore, the shot warranty specifications are defined for the mold. The molds are expected to produce 2,5 million shots during 5 years. The renovations of the mold are expected when the mold has produced 1.0m and 2,0m shots. In addition, the mold must include a cycle counter. The counter may not be able to reset. If possible the cycle counter should be countersunk, to secure against damage.

4.4.4 Maintenance of the molds

Normally the supplier of molds specifies the daily maintenance, cleaning etc. as well as one yearly inspection at minimum. The inspection procedure must be specified by the supplier of molds and be approved by Radiometer. The maintenance plan for the molds could for example be: Daily maintenance:

Check of Guide pins and bushings.

Lubrication.

Contacting surfaces at split line of the mold.

Controlled and cleaned.

Air escapes cleanup.

Every 6 month maintenance:

Mold dismantling in major parts, stationary part, moving part etc.

The parts cleanup.

The parts controlled for scratches, mark and wear.

Cooling checked and controlled under pressure.

Cold runner/hot runner controlled.

Gates controlled, size and wear.

Air escapes controlled and measured.

Every 12-month maintenance:

Mold dismantling complete.

The parts cleanup.

The parts controlled for scratches, mark and wear.

Cooling checked and controlled under pressure.

Cold runner/hot runner controlled.

Gates controlled, size and wear.

Air escapes controlled and measured.


69

4.5 Mechanical calculation of the micro sampler structure

The micro sampler is analyzed for three loading situations which represent the loading situation during sampling, during unavoidable mishaps as fall from hand and during transportation of the micro sampler.

4.5.1 The loading situation during assembly

In this section the capillary wire is analyzed for stress during the assembly process. It is

assumed that the needle presses on the capillary wire with force of 29.4 N. The maximum

stress will be expected in the thinnest area which is the bottom side of the capillary wire. As

shown from the formula below the applied stress is 4.6 MPa which is less when material

stress at break.

(

)

4.5.2 The reaction force during unavoidable mishaps as fall from hand

The reaction force during unavoidable mishaps fall from hand is analysis for parts of the micro sampler. The fall high is assumed to 1 m. Since the situation is very complex to calculate, here a simple model is employed. So it is assumed that the micro sampler falls from the hands of the user in 1 meters height during sampling. The idea is to find the resulting force, and it is assumed the micro sampler consists of a mass at the end of a spring, and it deflects as a spring when it hits the ground.

Figure 62 Sketch of top cover during assembly


70

To find the reaction force a simple calculation made on the given assumptions are made, with the use of energy balance and spring deflection force see formula here below.

The cross section area of the sampler is an estimate of its smallest cross section. The used Young’s modulus is the tensile modulus chosen for a specific material. The cross section for PP side is calculated from formula below, where

is the outer radius and is the inner radius.

(

)

(

)

The next step is to calculate the spring stiffness.

Figure 63 The simple model of the micro sampler


71

F

The deflections are found from the energy balance. It can be concluded that the deflection for in PP side is 2 time higher than the deflection in PETG side.

√

√

√

√

Finally the reaction force can be calculated.

The reaction force from PP is lower than the reaction force from PETG. That means the simple model show that PP work as shock absorber because that has low young modulus and the material can be compressed without using a high mass of reaction force.

4.5.3 Stress during transports the sampler

The micro sampler must resist to a compression by 3 kg during transport (compression under boxes in the container). A simple scenario is that the sampler compression with 3 kg in the end of the top cover. Furthermore one side of the micro simpler is fixed while the other side is free.

L1 L2

Ay

Ax

By

Figure 64 Sketch of the sampler with reactions forces


72

As first step the reaction force in y direction is found with using the static equation as shown

below. F is set as 30 N which gives 3 kg load press.

Moreover, the model is cut in 4 areas. The torque and stress are check for every area. The

areas are defined as: the green area, red area, blue area and black area. The torque is

plotted as a function of the length (se fig. 65). The maximum torque is applied in red area,

because this area has a thin thickness and it is next to the compressed force. The max torque

is 0.68 Nm. Furthermore the stress is also plotted as function of the length (see fig 67). The

maximum stress is applied in the red section of the sampler.

Green area Red area Blue area Black area

Figure 65 Sketch model which illustrated the cut areas

Figure 66 Turque function as the length


73

The maximum stress must be lower than the stress at break for the material to hold a 3 kg

load during the transport.

It can be concluded that the micro sampler can compress with 3 kg during the transportation

without its break.

4.6 Mechanical simulation Since the top cover is more critical than bottom cover, it’s analyzed by mechanical simulation

for inappropriate use, and stress applied during assembly process. It is carried out by the

Comsol mechanical software package.

4.6.1 The maximum pull force before twisting the bottom cover.

According to standard procedure of the micro sampler, after blood sampling the bottom

cover must be twisted to opening position before its pulls out. This simulation shows, how

much pull force is allowed, if the bottom cover tried to pull out, before it is twisted (when

the bottom cover is in the closed position). It is assumed that the pull force exists on the luer

and the undercut area of top cover. The simulation shows that the maximum force pull force

is 127.3 N on the top cover in z direction. The maximum expected deflection and Von Mises

stress are 36.1 µm and 27.9 MPa see fig.68 and 69.

Figure 67 Stress function as the length


74

4.6.2 Maximum twist angles of the top cover

This section simulated how much the allowed maximum twist angles are, if the user

twists the bottom cover in the opposite direction. The maximum allowed twist angles is

0.66 degrees and the deflection is 54.3 µm (see fig. 70 and 71).

Figure 69 Von mises stress at pull in z direction (magnification 1)

Figure 68 Displacement in z direction (magnification 10)


75

Furthermore, the maximum allowed reaction moment in this direction is 2.35 mNm. The Von

Misses stress is 28 MPa which is equal to the stress at break for the material. Please see fig.

72 and 73.

Figure 70 Max twist angle 0.66 ⁰ (magnification 10)

Figure 71 Displacement at twist angle of 0.66 ⁰ (magnification 10)


76

4.6.3 Maximum deflection on the capillary wire

The idea with this case of the exercise is to simulate to see what will happen if the capillary

wire is pressed to the side. The simulation shows that the Von Mises stress does not exceed

the stress at break. That means if the capillary wire, during the sampling or another

condition, is pressed to the side, it will not break.

Figure 72 Reaction moment (magnification 10)

Figure 73 Von Mises stress at max twist angle (magnification 10)

Figure 74 Capillary wire press to side (magnification 10)


77

4.6.4 Maximum press on the capillary wire

The maximum force as allowed on the capillary wire in negative z direction is simulated. It

can be relevant during the assembly process when the needle pressed on the luer interface.

The maximum allowed force in negative z direction on the capillary wire is 124.6 N which

means, it is not critical when the needle pressed on the luer. Furthermore the maximum

deflection and Von Misses stress are 5.7 µm and 28 MPa.

Figure 75 Von Mises stress when the capillary wire was press to side (magnification 1)

Figure 76 Displacement when the capillary wire presses in z direction (magnification 10)


78

4.6.5 Maximum press on the head of top cover

The head of the top cover is simulated to find the maximum bent deflection just before it

breaks. The maximum bent deflection is found to 0.57 mm and the maximum force on the

head to 4.8 N.

Figure 77 Von Mises stress on capillary wire when pressed in z direction

Figure 78 Displacement of head when it press down (magnification 10)


79

4.7 Conclusion and summary

The parts of the micro sampler are improved during the design calculation process.

Furthermore the data and the size of the injection molding machine are found. Lastly, the

parts are calculated and simulated to reify that the design can hold to the stress applied from

inappropriate use, during transportations and during assembly process.

Figure 79 Von mises stress when the head of top cover press down (magnification 10)


80

5. Injection molding simulation This chapter describes the simulation study of top and bottom cover of the micro sampler. Two cases of simulations have been performed, the first case was the top cover which is made of PETG and the second is the bottom cover which is made of PP. As a first step a solution for top and cover body by making a systematic set up simulations which include five series:

1. Fill shot series –The fill shot series should establish a relatively low pressure using an uncompleted filling of the parts. That means the packing pressure and packing time is zero during the series. The best parameters for injection rate, switch-over point and ram position until parts are filled about 98%, will be found.

2. Packing pressure series –The idea with this series is to find the optimal packing

pressure for the parts which gives the stable part weight, minimum sink marks and deflection (i.e. warpage).

3. Packing time series –The idea with this series is to find the minimum packing time for

the parts.

4. Cooling series: The idea with this series is to find the optimal cooling time for the parts.

5. Optimization series: The best theoretical cycle time of the part will be found during

this series. Furthermore, all the simulations data are collected in a process set up table, allowing a comparison of the simulation and analytical (process calculation). In addition the process set up table can be used for machine settings in the future. Lastly the two materials are compared regarding to viscosity and specific volume properties.

5.1 Simulation top cover In this section it is described how a systematic simulation for the top cover is performed.

5.1.1 Fill shot series for top cover

First, the packing pressure and packing/holding time is set to zero, to see how the material flows into the parts. The temperature, the rotation speed of the screw, the back pressure and the suck back position are set by the material supplier's recommendation in the software. The second step was to create a fine mesh with small elements for the 3D file. The software suggested a mesh size 2.01 mm 0.1 mm but the mesh size was too coarse for the part. Therefore mesh is set as 0.5 mm 0.05 mm which is a fine mesh.

Figure 80 Left: The top cover with 2.01 mm mesh. Right: The top cover with 0.5 mm mesh


81

The next step was to make a short study to find the best injection point place on the part. The injection point was placed in different positions on the part. It was difficult to fill the part when the injection point was placed on the top side, middle of part and on the luer cap. Therefore the injection point was placed in the bottom side of the part. So the external layer which has thinnest thickness can be molded first and accordingly the capillary wire and the head of the part molded.

Finally the fill shot series starts. During the series the optimal injection speed, cooling time, filling time, mold and melt temperature and the necessary clamping force will be found. Furthermore, the best found process parameter goes further to the next series. The switch over point is set high to ensure there will be enough residues cushion.

Fill shot series

Simulation Melt temp. [⁰C ]

Mold temp. [⁰C ]

Ram position [mm]

Switch over point [mm]

Injection speed [mm/s]

Filling time [s]

Pressure at switch over point [MPa]

Cooling Time [s]

Clamp Force [Ton]

1 260 23 25 10 50 0.379 180 9.32 0.80

2 260 23 25 10 100 0.359 180 9.86 1.56

3 260 23 25 10 150 0.15 180 11.3 1.67

4 270 37 25 10 150 0.11 180 13.2 2.57

Chosen simulation

270 37 25 10 150 0.11 180 13.2 2.57

Table 16 Process data during the fill shot series.

Figure 81 Left: The injection point placed on the top side. Right: The injection point placed on the luer cap

Figure 82 Left: The injection point placed on middle of the part. Right: The injection point placed on bottom side


82

The mold and melt temperature of simulation 1 and 2 are set by the material supplier's recommendation. But the melt and mold temperature are increased to maximum during the series because the part was difficult to fill. At the same time the injection speed is increased to 150 mm/s which is next to max injection speed of injection molding machine as is 161.12 mm/s (from technical data from the machine supplier). To ensure that the part fills and the fill time including in the cycle time of, machine is optimized see fig 83. The pressure at switch over point is very high because the part has a long flow length, complex geometry and viscosity of the material is high. But since the pressure at switch over point (180 MPa) does not exceed the maximum injection pressure of the injection molding machine (220 MPa from technical data of the machine) it could be accepted.

Figure 83 Fill time of the top cover at injection speed of 150 mm/s

Figure 84 Pressure at switch over point of the top cover at injection speed of 150 mm/s


83

The higher pressure at switch over point is, the higher clamp force is necessary to hold the mold closed during the filling phase. The necessary clamp force during the filling phase is 2.57 Ton (25 KN). The maximum clamp force from the injection molding machine is 25 Ton (250 KN) which is 10 times higher with the necessary clamp force.

Lastly, the part was analyzed for air traps, as shown in fig.86. The air traps are mostly located at the end and beginning of the part because they are the last areas to solidify out. The problem can be solved by creating an air channel into the mold for venting the air.

5.1.2 Packing pressure series for top cover

When the part was filled 99 %, the packing pressure and packing time is set on. The packing time was set higher up. The simulation is started with very low packing pressure and then increasing the packing pressure during the series until the weight of the part is stable.

Figure 85 Clamp force of the top cover at injection speed of 150 mm/s

Figure 86 Air traps of the top cover at injection speed of 150 mm/s


84

The best packing pressure is found to 162 MPa which is 90 % of the pressure at switch over point. The weight part is going to be stable as shown in fig 87.

Figure 87 The part weight as function of packing pressure.

The maximum values of the estimated sink marks and the volumetric shrinkage exist in the thick thickness areas of the part see fig 88 and 89. The thick areas are not critical for the assembly. Therefore maximum estimated sink marks and volumetric can be accepted.

2,760

2,780

2,800

2,820

2,840

2,860

2,880

2,900

2,920

0 50 100 150 200

We

igh

t o

f p

art

[g]

Packing pressure [MPa]

Packing pressure series

Simulation Packing Pressure [MPa]

Packing Pressure Time [s]

Estimated Sink mark [mm]

Volumetric Shrinkage [%]

Deflection All direction [mm]

Deflection In x direction [mm]

Deflection In y direction [mm]

Deflection In z direction [mm]

Part Weight [g]

1 54 10 0.283 13 0.256 0.135 0.0637 0.220 2.77

2 144 10 0.192 11.56 0.204 0.0600 0.0477 0.117 2.87

3 162 10 0.175 11.11 0.1824 0.0540 0.0433 0.0983 2.90

4 180 10 0.152 10.31 0.154 0.0488 0.0387 0.076 2.92

Chosen simulation

162 10 0.175 11.11 0.1824 0.0540 0.0433 0.0983 2.90

Table 17 Process data during the packing pressure series.


85

Furthermore the maximum deflections in the three directions (x,y,z) of the part also exist in

uncritical area. The critical area where the capillary wire exists is in the accepted zone which

is the greenish-blue and the green area. Please see figure from 90-93.

Figure 88 Estimated sink marks of the top cover at packing pressure 162 Mpa and packing time 10 s (magnification 1).

Figure 89 Volumetric shrinkage of the top cover at packing pressure 162 Mpa and packing time 10 s (magnification 1).

Figure 90 Deflection in the x direction for the top cover at packing pressure 162 Mpa and packing time 10 s (magnification 1)


86

Figure 91 Deflection in y direction for the top cover at packing pressure 162 Mpa and packing time 10 s (magnification 1).

Figure 92 Deflection in z direction of the top cover at packing pressure 162 Mpa and packing time 10 s (magnification 1).

Figure 93 Deflection in all direction for the top cover at packing pressure 162 Mpa and packing time 10 s (magnification 1).


87

5.1.3 Packing time series for top cover

The purpose of the series is to find the minimum packing time. Generally speaking the packing time is decreased until a stable weight is obtained in the part.

The packing time was decreased until the part weight was unstable and it occurred at 1.5 s as shown in the graph below (fig.94)

Figure 94 Part weight plotted function as packing pressure time.

At the same time, the volumetric shrinkage, deflections in all directions and sink marks are controlled because the packing time has influenced them. Further these parameters have been compared for packing time at 10 s., 1 s and 1.5 s (see figure 94). It’s clear to see that the volumetric shrinkage at 1.5 s and 10 s is almost the same but it change at packing time 1 s. It is very difficult to see the differences for deflection and sink marks because the material has an amorphous structure which has a low specific volume.

2,887

2,888

2,889

2,890

2,891

2,892

2,893

2,894

2,895

2,896

2,897

0 2 4 6 8 10 12

Par

t w

eig

ht

[g]

Packing pressure time [s]

Packing time series




Volumetric Shrinkage [%]





Part Weight [g]

1 162 10 0.175 11.11 0.1824 0.0540 0.0433 0.0983 2.90

2 162 1.5 0.175 11.10 0.1823 0.0543 0.0433 0.0982 2.90

3 162 1 0.178 12.95 0.1842 0.0560 0.0441 0.1024 2.89

4 162 0.5 0.179 12.95 0.1651 0.0590 0.0442 0.1022 2.88

Chosen simulation

162 1.5 0.175 11.10 0.1823 0.0543 0.0433 0.0982 2.90

Table 18 Process data during the packing time series


88

Figure 95 Compared volumetric shrinkage of top cover .Top: Volumetric shrinkage at 1 s packing time. Middle: 1.5 s packing time. Bottom: 10 s packing time (magnification 10).

1.0 s

1.5 s

10 s

Figure 96 Compared deflection in all direction of top cover .Top: Volumetric shrinkage at 1 s packing time. Middle: 1.5 s packing time. Bottom: 10 s packing time (magnification 10).

1.0 s

1.5 s

10 s


89

5.1.4 Cooling time series for top cover

The cooling time depends on the mold and melt temperature, injection speed and material properties. These series are analog with packing time series. You decrease the cooling time until the cavity obtains coarse ejector marks or until it obtain the surface temperature limits as given by the material suppliers. But it is not necessary in this case because it’s possible to read the best given cooling time from figure 98. The best estimated cooling time is chosen to 13.2 s because all the critical areas are ready to be ejected (greenish-blue areas see fig 98).

Figure 98 Time to reach ejection temperature for top cover at packing pressure 162 Mpa and packing time 1.5 s

Figure 97 Compared sink marks of top cover .Top: Volumetric shrinkage at 1 s packing time. Middle: 1.5 s packing time. Bottom: 10 s packing time (magnification 10).

1 s

1.5 s

10 s


90

5.1.5 Optimization series for top cover

The idea with this series is to optimize the opening and closing speed for moveable part and

the minimum break/robot time to obtain the best cycle time. The opening and closing speed

of the machine is assumed to 1.4 s which is the dry cycle (trockenlauf) of the injection

molding machine (see technical data of the machine in the appendix A) and the robot

time/break time is assumed to 1 s.

5.2 Simulation bottom cover

This section describes how to make a systematic simulation for the bottom cover.

5.2.1 Fill shot series bottom cover

The method is the same as applied for the top cover. First, the packing pressure and packing time are set to zero, to see how the material flows into the parts. The temperature, the rotation speed of the screw, the back pressure and the suck back position are set by the material supplier's recommendation of the software. The mesh generation size is set as top cover 0.5 mm 0.05.

. Figure 99 Mesh generation with 0.5 mm of the bottom cover

The same injection molding machine is chosen as top cover with a screw diameter ( ) of Ø18 mm because the part has approximately same size as top cover. There are two ideal areas on the part to place the injection point. One is the bottom of the part and the other is the side of the part. The injection point is placed in the side of the part, because it was approximately the middle of part.

Next is to simulate the fill shot series. During the phase the best injection speed, cooling time, filling time, mold and melt temperature and the necessary clamping force will be found. Furthermore the best found values goes further to the next series. The switch over point is set high to ensure there is enough residual melt cushion.


91

Fill shot series

Simulation Melt temp. [⁰C ]

Mold temp. [⁰C ]

Ram position [mm]

Switch over point [mm]

Injection speed [mm/s]

Filling time [s]

Pressure at switch over point [Mpa]

Cooling Time [s]

Clamp Force [Ton]

1 230 50 18 10 50 0.159 39.94 5.16 0.327

2 230 50 18 10 100 0.090 45.46 5.22 0.373

3 230 50 18 10 150 0.058 55.07 6.1 0.46

Chosen simulation

230 50 18 10 150 0.058 55.07 6.1 0.46

Table 19 Process data during the fill shot series

The melt and mold temperature are set by the material supplier's recommendation. The injection speed increased during the series next to max and thereby the best fill time is obtained (see fig.100). Although the injection speed is set high and the part has long flow length, the pressure at switch over point is low (see fig 101). It is because the material has god flowability.

Figure 100 Fill time of the bottom cover at injection speed 150 mm/s

Figure 101 The pressure at switch over point for bottom cover at injection speed 150 mm/s


92

The clamp force during the fill series is low because pressure at swicht over point is low. The lower pressure at swich-over point is, the lower clamp force.

The last simulation analysis during the fill series is air traps, as shown in fig.103. The air traps are mostly located at the end and beginning of the part because it is the last area to fill. The problem can be solved by creating an air channel into the mold to vent the air.

Figure 102 Clamp force during fill series for the bottom cover at injection speed 150 mm/s

Figure 103 Air traps for the bottom cover at injection speed 150 mm/s


93

5.2.2 Packing pressure series for bottom cover

When the part was 99 % filled, the packing pressure and packing time were set and the packing time was set higher. Furthermore the simulation start with very low packing pressure and the packing pressure increases until the weight of the part is stable (same method as top cover).

The optimal packing pressure is found at 90 MPa. The weight part is going to be stable as shown in fig 104. Furthermore, volume metric shrinkage, deflection in all direction and the estimated sink marks are compared with packing pressure at 60 MPa, 90 MPa and 100 MPa as shown in the fig 105 -fig 108.

Figure 104 Part weight plotted as function of packing pressure.

0,54

0,55

0,56

0,57

0,58

0,59

0,6

0,61

0,62

0 20 40 60 80 100 120

Par

t w

eig

ht

[g]

Packing Pressure [MPa]

Packing pressure series




Shrinkage Volume Metric [%]





Part Weight [g]

1 30 10 0.170 13.21 0.482 0.136 0.1907 0.468 0.55

2 60 10 0.070 11.18 0.283 0.077 0.1125 0.277 0.60

3 90 10 0.055 9.21 0.178 0.074 0.0846 0.174 0.61

4 100 10 0.051 8.71 0.134 0.072 0.0859 0.132 0.61

Chosen simulation

90 10 0.055 9.21 0.178 0.074 0.0846 0.174 0.61

Table 20 Process data during the packing pressure series


94

In this case of simulation the differences at low and high packing pressure are clearly seen. The estimated sink marks, volume shrinkage, and deflections in all directions are nearly same at 90 MPa and 100 MPa packing pressure, but they are rather different at 60 MPa packing pressure.

Figure 105 Compared sink marks of bottom cover .Top: Sink marks at 100 MPa packing pressure. Middle: Sink marks at 90 MPa packing pressure. Bottom: Sink marks at 60 MPa packing pressure (magnification 10)

100 MPa

90 MPa

60 MPa

Figure 106 Compared volumetric shrinkage of bottom cover .Top: Volumetric shrinkage at 100 MPa packing pressure. Middle: Volumetric shrinkage at 90 MPa packing pressure. Bottom: Volumetric shrinkage at 60 MPa packing pressure (magnification 10).

100 MPa

90 MPa

60 MPa


95

The estimated sink marks and the volume metric shrinkage exist in the thickest thickness of the part. The max estimated sink mark is 0.05 mm and it is acceptable because it exists in uncritical areas.

Figure 108 Sink marks of bottom cover at 10 s packing time and 90 MPa packing pressure (magnification 1).

Figure 107 Compared Deflection in all direction of bottom cover .Top: Deflection in all direction at 100 MPa packing pressure. Middle: Deflection in all direction at 90 MPa packing pressure. Bottom: Deflection in all direction at 60 MPa packing pressure (magnification 10).

100 MPa

90 MPa

60 MPa


96

Furthermore the maximum deflection in the three directions (x,y,z) of the part exist in uncritical area. The critical areas are these areas where it assemblies with the top cover and the needle. These areas are in the accepted zone and the accepted zone is the greenish-blue and the green area (see figure from 110-111).

Figure 109 Volumetric shrinkage of bottom cover at 10 s packing time and 90 MPa packing pressure (magnification 1)

Figure 111 Deflection in x direction for bottom cover at 10 s packing time and 90 MPa packing pressure (magnification 1)

Figure 110 Deflection in all directions of bottom cover at 10 s packing time and 90 MPa packing pressure (magnification 1)


97

5.2.3 Packing time series

The purpose of the series is to find the minimum packing time using the same method as top cover.

The packing time is decrease until the part weight stared to decrease. The minimum packing time is found at 2 s packing time (see fig 112). At the same time the volume metric shrinkage, deflection in all directions and the estimated sink marks are compared with different packing time are collected for 2 s, 1 s and 0.5 s in fig 113-115.

Packing time series




Shrinkage Volume Metric [%]





Part Weight [g]

1 90 10 0.055 9.21 0.178 0.074 0.0846 0.174 0.61

2 90 5 0.055 9.21 0.173 0.073 0.077 0.170 0.61

3 90 2 0.40 9.21 0.173 0.1636 0.077 0.170 0.61

4 90 1 0.40 13.24 0.224 0.163 0.164 0.155 0.60

5 90 0.5 0.40 20.5 0.392 0.163 0.173 0.382 0.57

Chosen simulation

90 2 0.40 9.21 0.173 0.1636 0.077 0.170 0.61

Table 21 Process data during the packing time series

0,565

0,57

0,575

0,58

0,585

0,59

0,595

0,6

0,605

0,61

0,615

0 2 4 6 8 10 12

Par

t w

eig

ht

[g]

Packing time [s]

Figure 112 The part weight plotted as function of packing time


98

Figure 113 Compared sink marks of bottom cover .Top: Sink marks at 2 s packing time. Middle: Sink marks at 0.5 s packing time. Bottom: Sink marks at 1 s packing time (magnification 10)

2 s

0.5 s

1 s

Figure 114 Compared deflection in the all direction of bottom cover .Top: Deflection in the all direction at 2 s packing time. Middle: Deflection in the all direction at 1 s packing time. Bottom: Deflection in the all direction at 0,5 s packing time (magnification 10).

2 s

1 s

0.5 s


99

5.2.4 Cooling time series

The optimal estimated cooling time is chosen at 6.1 s which is the green areas in fig 11, because 80%- 90 % of the part is ready for ejection and there is only one uncritical areas which is in the red and yellow area (see fig.116).

Figure 116 Time to reach temperature for bottom cover at 2 s packing time and 90 MPa packing pressure (magnification 1)

Figure 115 Compared volumetric shrinkage of bottom cover .Top: Volumetric shrinkage at 2 s packing time. Middle: Volumetric shrinkage at 0.5 s packing time. Bottom: Volumetric shrinkage at 1 s packing time (magnification 10)

2 s

0.5 s

1 s


100

5.2.5 Optimization series

The optimized cycle time is expected to 10.56 s (using the same parameters of dry time and

robot time as for top cover).

5.3 Theoretical Process set up table

The idea to make a theoretical process set up table is it can be used for machine settings in the future. Therefore all the simulation data are collected in a table and all the other process data are set by the material supplier's recommendation.

5.3.1 Theoretical process set up table for top cover

Theoretical process set up table for top cover

Cylinder temperature [⁰C]

Nozzle Zone 1 Zone 2 Zone 1

265 250 240 230

Machine information Machine type Engel ES 80/25 250 kN

Mould height min. 150 mm

Screw diameter Ø18 mm

Max injection speed 161.12 mm/s

Max injection pressure 220 MPa

Material information Type of material Easter GN002-PETG

Max drying temperature 66 ⁰C

Drying time 4 h

Machine setting from simulation result Melt temperature 270 ⁰C

Mold temperature 37 ⁰C

Pressure at switch over point 180 MPa

Clamp force during filling 2.57 Ton (25,7 kN)

Injection speed 150 mm/s

Ram position 25 mm

Suck back position 5 mm

Switch over point 10 mm

Fill time 0.11 s

Packing Pressure 162 MPa

Packing time 1.5 s

Cooling time 13.2 s

Expected cycle time 17.21 s

Comment and information An air channel in the mold must be created to avoid air traps.

The air channel should be cleaned after 24 hours production.

The guide pins should be lubricated after 24 hours production.

Table 22 Theoretical process set up table for top cover


101

5.3.2 Theoretical process set up table for bottom cover

Theoretical process set up table for bottom cover

Cylinder temperature [⁰C]

Nozzle Zone 1 Zone 2 Zone 1

225 215 205 195

Machine information Machine type Engel ES 80/25 250 kN

Mould height min. 150 mm

Screw diameter Ø18 mm

Max injection speed 161.12 mm/s

Max injection pressure 220 MPa

Material information Type of material A.schulman Polyfort PP 1030

Machine setting from simulation result Melt temperature 230 ⁰C

Mold temperature 50 ⁰C

Pressure at switch over point

55.07 MPa

Clamp force during filling 0.46 Ton (4.6 kN)

Injection speed 150 mm/s

Ram position 18 mm

Suck back position 5 mm (10 % of ram position)

Switch over point 10 mm

Fill time 0.058 s

Packing Pressure 162 MPa

Packing time 2 s

Cooling time 6.1s

Expected cycle time 10.56 s

Comment and information An air channel in the mold must be created to avoid air traps.

The air channel must be cleaned after 24 hours production.

The guide pins must be lubricated after 24 hours production.

Table 23 Theoretical process set up table for bottom cover


102

5.4 Quality control demands

The idea with this section is to convert the simulation result to quality control demands. The quality control has two different types of characteristics. One type is about the material characteristics which indicate the strength and the hardness of the material and the other type is about the geometric characteristics. Together the two characteristic types control the parts’ functional properties. To control the material characteristics, the process results from the simulation are converted as a list of process control requirement because the process conditions (pressure, temperature and speed) have an influence on the molded product´s characteristics. Furthermore the deflection results from the simulation are converted as geometric characteristics. To control that, the GPS-system will be used. GPS means Geometrical Product Specification and can be interpreted as form, function and specifications (see next chapter 6).

5.4.1 Process control requirement of top cover

The process control demands of the top cover as list following:

Max estimated sink marks 0.175 mm.

Max volume metric shrinkage 11.10 %.

The optimal part weight 2.90 g.

No burn marks (diesel effect).

No significant flash.

No yellowish surfaces.

No significant gate rest.

5.4.2 Process control requirement of bottom cover

The process control demands of the top cover as list following:

Max estimated sink marks 0.40 mm.

Max volume metric shrinkage 9.21 %.

The optimal part weight 2.90 g.

No burn marks (diesel effect).

No significant flash.

No yellowish surfaces.

No significant gate rest.


103

5.5 Comparison of materials

In this section the two simulated thermoplastic polymers will be compared with regards to

viscosity and specific volume. The two materials have different configuration of their

polymer chains. PETG which is the used material for top cover has polymer chains with

random state (amorphous) and PP which is the used material for bottom cover has polymer

monomers with some regions in ordered state (crystalline) and some regions in random

state, therefore PP is classified as semi-crystalline. The differences between the amorphous

and semi-crystalline are list following:

5.5.1 Comparison viscosity

There are big differences between the viscosities of these two materials. PETG has higher viscosity then PP. It was one of the reasons why the injection/fill pressure of PETG was higher than PP. Lower viscosity of plastic gives low injection pressure (as shown in the formula below). Moreover an important point is, since the fill speed is constant, the plot of PP can be assumed linear (the shear stress is proportional with the viscosity). That means if you increase the mold and melt temperature, the viscosity of PP decreases (see fig 117).

Semi-Crystalline

Sharp melting point

Ordered and repeating molecular order

Reinforcements improve physical

properties

Part usually opaque due to crystalline

structure

Good mechanical properties

Resilient

Modulus (strength) retained up to and

approaching melting point

Amorphous

No true melting point

Has a glass transition temperature (Tg)

Random Molecular chain orientation.

May give transparent look

Modulus (strength) gradually decreases

then falls off rapidly

Is a tough, rigid material with good

creep resistant


104

5.5.2 Comparison specific volume

The graph of pvT shows that the specific volume variation of the PP is higher than the specific volume relation to PETG. It means you can fill more into PP during the packing pressure series and packing time series. Therefore a higher effect at different packing pressure during the packing pressure series for PP compared with packing pressure series of PETG could be observed. The higher packing pressure, the less specific volume will be obtained. Furthermore the graph also shows that if you keep the pressure constant and increase the melt temperature you will get a more specific volume of the polymers.

Figure 117 Viscosity plots at different temperature. The upper plots are for PETG and the lower are for PP

Figure 118 PVT plots at different temperature. The upper plots are for PP and the lower are for PETG


105

5.6 The 6 Process parameters which have influenced on the molded part

There are 6 important parameters of the injection molding machine which must be set in the

following to obtain less shrinkage, warpage, sink marks, short cycle time, glossy surface,

flashes and diesel effect (burn marks).

Injection speed – To optimize the cycle time and get a better welding line of machine the injection speed must be set high. But if the quality of part is important regarding warpage and shrinkage the injection speed must be set low. Furthermore high injection speed gives higher filling pressure and diesel effect (burning marks).

Mold temperature – The mold temperature must be set high to get a better glossy surface of the injected molded parts, if the materials have poor flowability and if the flow lengths of the parts are long. But higher mold temperature gives more cooling and packing times and thereby longer cycle time. Furthermore high mold temperature gives more shrinkage and warpage in the molded parts.

Melt temperature – High melt temperature gives less shrinkage and warpage in the injected molded parts, better welding line and less filling pressure. On the other hand the parts needed longer cooling and packing pressure time.

Packing pressure – Low packing pressure gives sink mark, unfilled injected molded

parts and unstable weight. Too high packing pressure gives flashes or the parts will obtain high gate rest. The packing pressure must be high to obtain less shrinkage, warpage and uniformly weight.

Packing time – Low packing time gives sink mark, unfilled injected molded parts and

unstable weight. High packing time gives long cycle time, higher gate rest and flashes on the parts. The packing time must be high to obtain less shrinkage and warpage, as well as uniformly weight.

Filling pressures – High filling pressure a better welding line, less shrinkage and

warpage. Low filling pressure gives unfilled injected molded. The filling pressure depends on the injection speed, ram position, melt and mold temperature. The higher the injection speed and the ram position are, the higher the filling pressure is. And the higher the melt and molt temperature are, the lower the filling pressure is.

5.7 Conclusion and summary The top cover was very difficult to fill and therefore the filling pressure was rather high (180 MPa). This is because the material has a high viscosity and the very complex geometry which consists of a capillary wire, luer cap with integral hinge. However, this problem was solved by making an optimization study of the injection point position. Furthermore the parts have a big sink marks but it can be accepted because these areas were uncritical. The expected cycle time is found to 17.2 s which is at the same level as other parts with similar size. Lastly there were air traps in the part and that was solved by suggesting creating an air channel i.e. vents in the mold.


106

The next simulated part was the bottom cover and it fills easily because the material has better flow ability and the geometry of the part wasn’t complex. There are some sink marks on the part but it is acceptable because these are in the uncritical areas. Furthermore the expected cycle time is found to 10.58 s which is very satisfactory. Lastly there were air traps in the part and it was solved by suggesting creating an air channel to vent mold.

The analytical (process calculations) is compared with the injection molding simulation and they showed good agreement to each other (see table 24 and 25) An example is the pressure drop calculation both for bottom and top cover. They only range with 12 % deviation. Furthermore, the ram position and the suck back position from the analytical have a good agreement to the simulation. However there is a big deviation range for packing and fill time. It is because that the gate size was different in the simulation software.

Table 24 The analytical compared with the simulation for bottom cover.

Process data Simulated Top cover Analytical Top cover

Pressure at switch over point 180 MPa 164 MPa

Clamp force during filling 2.57 Ton (25,7 kN) 2.6 Ton

Injection speed 150 mm/s 160 mm/s

Ram position 25 mm 24.7 mm

Suck back position 5 mm 5 mm

Switch over point 10 mm 10 mm

Fill time 0.11 s 0.064 s

Packing Pressure 162 MPa 131.4 MPa

Packing time 1.5 s 0.63 s

Cooling time 13.2 s 10.5 s

Expected cycle time 17.21 s 13.61 s Table 25 The analytical compared with the simulation for top cover.

Process data Simulated bottom cover Analytical bottom cover

Pressure at switch over point 55.07 MPa 56.2 MPa

Clamp force during filling 0.46 Ton (4.6 kN) 0.135 Ton

Injection speed 150 mm/s 160 mm/s

Ram position 18 mm 24.09 mm

Suck back position 5 mm 5 mm

Switch over point 10 mm 10 mm

Fill time 0.058 s 0.015 s

Packing Pressure 162 MPa 45 MPa

Packing time 2 s 1.29 s

Cooling time 6.1s 6.4 s

Expected cycle time 10.56 s 10.08 s


107

6. Geometrical product specification (GPS) GPS is the modern and updated symbol language that is used for tolerancing and of the 2D engineering drawings. GPS is developed by the International Organization for Standardization (ISO). GPS - standards developed by ISO technical committee ISO / TC 213th. GPS is internationally recognized and established as a national standard in more than 30 European countries. In addition, GPS is a stronger tool than the traditional tolerancing. “The basis for GPS tolerancing is traditional geometrical tolerancing, but used in a new and

different way” (Per Bennich, 2005).

6.1 Introduction to GPS

GPS can be interpreted as form, function and specifications, and GPS controls the geometric

characteristics of the specimen. Because of increasing globalization, it is important that all

the details on the item's function form and tolerances are described clearly.

A GPS drawing is a legal document. It means that it has to do with operations obtained from the workshop standards. When dealing with GPS, you have to think 3D instead of 2D drawings. You need Datum system and TED goals (theoretical exact dimension). There must be described control methods, surfaces, surface imperfections and edges. In general, GPS tolerancing reverts in better economy and better products. “Specification uncertainty can create significant legal and economic problems if the drawing

is used for subcontracting or outsourcing of manufacturing” (Per Bennich, 2005). GPS must be unconditional and preferably used for critical tolerance requirements on a

drawing and tolerance requirements which have a direct influence on the item's functions.

GPS is a technical necessity for drawings and can express clear design intent. Uniqueness of

drawing tolerancing has been an increasing necessity because tolerances have become

smaller and smaller, and because the drawings are used increasingly in the context of

outsourcing of manufacturing products.

“A term that is key to understanding the advantage of GPS is specification uncertainty” (Per Bennich, 2005). The traditional tolerancing is unique and only works when the items produced are free from

defects in shape, and when all angles of the subject are perfect. GPS is designed to cope with

this problem. GPS tolerancing retains its uniqueness on the manufactured item, even when

acting form and angular deviations. GPS works as a toolbox, where the designer can take the

tools, as he needs and leaves the rest in the toolbox. With GPS tolerances can be expressed

in more detail. This means that GPS can simulate real part very closely. With GPS the

constructor can incorporate much more information in the drawing and the information can

be used to select the technically and economically optimal production methods. The

requirement for measurement methods has been built into the GPS tolerancing. This means

that the existing measurement techniques can be used much more efficiently and with less

uncertainty.


108

GPS is characterized by:

Masterplan

Approach based on functionality

Skin model

Rule of taking measurement uncertainty into account in tolerance verification

6.1.1. ISO 14638 – Masterplan

GPS matrix system is defined in ISO / TR 14638 and that described the masterplan in the field

of GPS shown in the table 26.

T

h

i

s

s

y

s

t

e

m

d

i

Furthermore standards contained in the general GPS matrix, a number of standards are

grouped as:

The fundamental GPS – standards – are the most basic GPS - standards and are

published by: ISO / TR 14638 and ISO 14659 where that describe the basic rules of

GPS.

The Global GPS – standards – contain the global rules for how tolerances must be

interpreted, and the whole concept universe there underlies for GPS - System and

GPS tolerancing.

The

fu

nd

ame

nta

l GP

S –

sta

nd

ard

s

The Global GPS – standards GPS or related standards, which treat or affect several or all GPS standards

General GPS-matrix (standard )

1. Size 11. Orientation

2. Distance 12. Location

3. Radius 13. Circular run out

4. Angle 14. Total run out

5. Angular Size 15. Datum

6. Angular Distance 16. Roughness profile

7. Form of line independent of datum

17. Waviness profile

8. Form of line dependent on datum

18. Primary profile

9. Form of surface independent of datum

19. Surface imperfection

10. Form of surface dependent on datum

20. Edge

Standard in the Complementary GPS matrix Process specific standard chain Machine Element-specific standard chain

Table 26 ISO 14638 – Masterplan in field of GPS


109

Standard in the Complementary GPS matrix – Is the process-specific general

tolerance standards

Moreover, the general GPS standards are arranged in the chain link 6 in the general GPS

matrix. Chain link defines specifications operator 1-3 and 4-6 chains defines verifications

operator. Please see table 27.

6.1.2. Functionality approach

The GPS gives a detailed description of geometrical features linked to functional properties. An example of that could be the circle diameter. You can define a circle diameter in several ways which are the following:

1. Two point circle 2. Largest inscribed circle 3. Least squares circle 4. Least circumscribed circle 5. Circumference divided by Pi

6 chain links

1 2 3

Co

mp

aris

on

bet

wee

n d

efin

ed

and

mea

sure

d c

har

acte

rist

ic

4 5 6 Product documentation indication Specific codes

Definition of tolerance Theoretical definition of tolerance and their numerical values

Definitions of characteristics of actual (real) feature Specifications operator

Assessment of the workpiece deviations Comparison with specific limits

Measurement equipment Characteristics of measurement

Calibration requirements Measurement standards

Specification of GPS – characteristic Verifikation af GPS – characteristic

Table 27 ISO 14638 – The 6 chain links of GPS

Figure 119 ISO 14638 – Diameter problem


110

This circle example gives the designer a lot of possibilities, e.g. the designer can indicate a circle diameter as two point circles, to obtain relative low form error and obtain functionality which is mainly governed by size. Furthermore the designer can use the largest inscribed circle for bores hydraulic parts. The diameter which is indicated by circumscribed circle and circumference divided by Pi are useful, when fitting together deformable parts, e.g. a lid for a bucket.

6.2 The skin model of GPS

The skin model is defined as non-ideal features on a part/work piece (ISO 14660). It means

when you construct in the CAD program all surfaces and holes are perfect. But no perfect

geometry can be achieved in reality. No injection molding parts have ideal surfaces; in

addition they have sink marks and volumetric shrinkages. The angles are different from the

nominal angles and holes have form errors. Also, the Center lines are not straight (this

problem is illustrated in fig. 120). But with using the GPS tolerancing, with large number of

measurements points, it is possible to give a realistic picture of the geometry of an object.

An example of that is given in the book “Geometrical metrology and machine testing” by

L.DE Chiffre (see fig. 121).

Figure 120 Skin model illustration by top and bottom cover (magnification 10)

Figure 121 Operation according to the skin model (L.De Chiffre 2011)


111

6.1.3. 14253-1 –Rules on conformity

ISO 14253-1 set a framework for how a principle can be introduced in commercial

transactions where work pieces or measuring equipment are evaluated against a

specification. E.g. in a drawing specification it is very clear what the limits of the tolerance

are. It could be upper and lower tolerance values for diameter or length. However, when a

workpiece is measured, it is to confirm that it is in or outside tolerance areas. In fig.122 it is

illustrated how the tolerance range diminished by measuring uncertainty following

indications in the GUM (ISO, 2008).

Figure 122 Rule of conformity verification by ISO14253-1

1 Specification zone (tolerance or maximum permissible error) 2 Out of specification 3 Conformance zone 4 Non-conformance zone 5 Uncertainty range The conformance zone is the tolerance reduced by the measuring uncertainty. The non-conformance zones are the areas outside the tolerance by more than the measuring uncertainty. The uncertainty ranges are the areas where conformance or non-conformance cannot be determined. Furthermore C is the workpieces design /specification phase, D is the manufacturing process and U is the measurement uncertainty in the fig.123. Lastly, the rule of proving conformance with specification according to ISO 14253-1 is illustrated in figure 123.


112

6.3 The critical interfaces of the sampler

The filter disc is neglected in this section because it has not influenced on the assembly

session. All the interfaces which have bodily contact with other interfaces are defined as

critical due to the assembling and the functionality of micro sampler. The interfaces which

are most critical are painted by the red line in the fig. below. Furthermore the interfaces

which fit with each other by integral hinge and press fits is defined as less critical interfaces

and they are painted by orange line.

Figure 124 The most critical areas of top and bottom cover

Figure 123 Rule of proving conformance with specification according to ISO 14253-1. Top: measuring uncertainty subtracted from specification zone. Bottom: measuring uncertainty added to measurement result


113

6.4 Tolerance chain calculation

Tolerance chain calculations to the most critical interfaces of the micro sampler in x and y directions are performed. The most critical interfaces in x direction are located between top cover and bottom cover (fig 126) rubber cap and top cover (fig 125). The tolerance chains are shown in formula below where clearance between the parts and is the tolerances in worst case.

‘

The tolerance chain calculation between top cover and bottom cover are very complex. The chain start from the cut area of top cover to end ( ) and goes in negative direction (-x) from the end at top cover to the beginning ( ), continues from the beginning of luer to end of the needle ( ) in positive direction of x axis. Further the chain continues to which is the length between the end of the needle to the beginning of the cut area. Lastly it can continue to which is the diameter of the fixed button.

Figure 126 Tolerance chain between top and bottom cover. Top: Localized tolerance chain. Bottom: Sketch of tolerance chain

Figure 125 Tolerance chain between rubber cap and top cover


114

Furthermore, the most critical interfaces in y direction exist in three sections and they are the following: Section 1 where it’s located between top cover and rubber cap. Section 2 located between mixing wire and top cover and section 3 between top cover and bottom cover.

6.5 Demands for the sampler Based on the GPS philosophy, no planes, surfaces, edges or cylinders are perfect. Therefore,

some requirements are listed for the critical areas and subsequently converted to to GPS

tolerance symbols. The GPS tolerance symbols unlock the imperfect geometries within a

frame.

6.5.1 Design specification

The design of micro sampler must comply all requirements for VTC specification to “safe

PICO” point .3.3.1-28 to 3.3.1-43. In addition, the injection molded parts must be product of

a polished surface to avoid burrs. Furthermore the micro sampler must be transparent, so it

possible to detect the light from the blood gas analyzer and at the same time the user can

see the blood in the micro sampler.

6.5.2 Requirement to Dimensision of the sampler parts

The parts dimensions are the important in relation to the part, so it can be assembled easily

without using a lot of stress. In addition, the dimensions have big influence on the usability

and performance of the micro sampler. Skew dimension gives bad functionality of the micro

sampler.

Figure 127 Tolerance chain in Y direction. Left: Tolerance chain cap and top cover. Middle: Tolerance chain magnet and capillary wire. Right: Tolerance chain top and bottom cover


115

Moreover, skew dimensions may pose risk for leaks between the parts. Requirements to the

dimension are listed in the following:

• Minimal warpage.

• The part must be cylindrical (specified In the GPS drawing).

• Minimal suctions (sink marks).

• Minimal flash (flash).

• Sides of the parts must be straight (specified In the GPS drawing).

• The parts must be symmetrical (specified In the GPS drawing).

6.5.3 Requirement to surface of the parts

The contact surfaces are the important elements that must have approximate coefficient of

friction between the top cover and the rubber cap. The requirement is that the friction force

between the components must be higher than the force applied during sampling. Otherwise,

there is risk for the rubber cap to fall during blood sampling. Requirements to the contact

surfaces are listed in the following:

Fine surface roughness (specified In the GPS drawing).

No nicks.

No weld line.

No burrs.

6.6 Convert the demands of the sampler to GPS tolerance symbols

The requirements to the dimensions and surfaces convert to GPS tolerance symbols. The

roughness of the critical surface controlled by roughness profile and the other requirement

to the micro sampler dimension controlled with the GPS tolerance symbol are as followed:

Straightness — A condition where all points are in a straight line, the tolerance

specified by a zone formed by two parallel lines.

Flatness — All the points on a surface are in one plane, the tolerance specified by a

zone formed by two parallel planes.

Roundness or Circularity — All the points on a surface are in a circle. The tolerance

is specified by a zone bounded by two concentric circles.

Angularity — The condition of a surface or axis at a specified angle (other than

90°) from a datum plane or axis. The tolerance zone is defined by two parallel


116

planes at the specified basic angle from a datum plane or axis.

Perpendicularity — The condition of a surface or axis at a right angle to a datum

plane or axis. Perpendicularity tolerance specifies one of the following: a zone

defined by two planes perpendicular to a datum plane or axis, or a zone defined by

two parallel planes perpendicular to the datum axis.

Parallelism — The condition of a surface or axis equidistant at all points from a

datum plane or axis. Parallelism tolerance specifies one of the following: a zone

defined by two planes or lines parallel to a datum plane or axis, or a cylindrical

tolerance zone whose axis is parallel to a datum axis.

Concentricity — The axes of all cross sectional elements of a surface of revolution

are common to the axis of the datum feature. Concentricity tolerance specifies a

cylindrical tolerance zone whose axis coincides with the datum axis.

Position — The idea with using this tolerance is to lock the location and the

orientation of the tolerance set element relation to one or more datum planes. In

addition the position symbol controls both the location (distance), orientation

(parallelism) and form (flatness).

6.7 Process window

As a part of the verification a process window has to be established. The process window consists of the parameters, which has influence on the K-, and F-dimensions of the part (according to GPS the part drawing). To establish an efficient process control, the K-dimensions have to be measured identical to the procedures during production. F-dimensions must be in “balance” before measurement, and prove there is a correlation between the F- and K-dimensions. The resting time for the parts, to be in “balance”, is for amorphous plastic materials 24 hours and for semi crystalline materials 14 days (according to Radiometer Medical ApS molds specification).

6.8 Tolerancing indication on drawing

The tolerancing on the drawing for top and bottom cover indicate the following:

The most critical areas – tolerancing by the tolerance chain calculation

Less critical areas – tolerancing by ISO standard DN 812.


117

6.9 2D technical drawing of Top cover


118

6.10. 2D technical drawing of bottom cover


119

7. Test of sampler The purpose with this chapter is to test the micro sampler for functionality and usability. To test the functionality of the micro sampler, two kinds of test are performed. One is a filter test where the performance of two filters are tested linked to flow rate and liquid. The other test is a draw test, where the performance of the capillary wire of the micro sampler is tested linked to draw blood samples into the blood gas analyzer. The idea with the usability test is that the micro sampler will be presented for the users at Herlev hospital in Herlev. Afterward the users evaluated the micro sampler compared with the current Radiometer sampler.

7.2 Functionality test of the micro sampler

The functionality test consists of two tests, where one is filter test and the second one is

draw test. The two tests together give a representation of the functionality of the micro

sampler.

7.2.1 Filter test

Two kinds of the tests of the filters are performed. One is the flow test where the flow

through the filter is tested linked to compression. The second one is the leak test where the

filter is tested for leaking at different pressure after it was filled with liquid.

For the tests two types of filters are used. The one filter is made of PE blended with a self-

sealing additive. When the additive comes into contact with the liquid, it dissolves into the

liquid and forms a highly viscous sludge, which has the effect of blocking the pores (i.e. liquid

or air can no longer pass through the filter). According to the filter recommended the

thinnest flat shape must be around 0.5 mm. The other filter type is MUNKTELL glass

microfiber filter papers (XA5). This filter is hydrophobic. The functionally is same as PE filter

but the difference is that the Munktell filter doesn’t have any additive. The microfiber is

blocking for the cells of the blood and thereby liquid can no longer pass through the filter.

Furthermore the filter test is performed by VTC (Vented Tip Cap) test setup from Radiometer

(see fig. 128), and the using procedure of the flow test is the following:

Connect the core to the flow meter;

Put the filter into the core;

Put the rubber disc on the filter;

Compress the filter and the rubber disc by adjusting the micrometer screw gauge;

Get the flow rate through the filter.

Flow test of filter:

The compression of the filter is set variable during the flow test. The interval goes from 0,10

mm to 0,45 mm which is the upper and lower limit for the compression based on the

tolerance chain calculations (in worst case). The default pressure during the test is 0,2 bar.


120

Figure 129 Sketch of the flow test

Figure 128 The filter test set up

Table 28 The flow test result (average and STD of 6 repeated measurements)


121

The PE- filter has better flow ability than micro-glass filter. Besides, because the micro-filter is softer than PE-filter, it compresses more and thereby the flow rate decrease. Liquid test:

The liquid test of the filter is performed with the same test setup as flow test. Here liquid is

used instead of air. The filter is default compressed to 0, 25 mm which is the nominal

compressing of the filter (from the tolerance chain calculation). The pressure hold time is set

3,5 s (according to VTC test requirement). The pressure on the filter starts low and increases

during the test to 5 bar (50 % of pressure test from VTC). The using procedure of the liquid

test is listed in the following:

Connect the core to the manometer (pressure –meter);

Put the filter into the core;

Put the rubber disc on the filter;

Compress the filter and the rubber disc by adjusting the micrometer screw gauge to

2,5 mm;

Pump pressure into the system by a hand pump;

Visual check of the filter for leak.

0

100

200

300

400

500

600

700

800

0 0,1 0,2 0,3 0,4 0,5

Flo

w r

ate

[m

L/m

in]

Compression [mm]

Microglas filter

PE-filter

Figure 130 Compression of filters plotted as function of flow rate at 0,2 bar


122

Figure 131 The sketch test setup of the leak test

The liquid test is performed for both filters. The two filters stand to 5 bar during 3,5 s without leaking. But the micro glass filter has a poor resistant to liquid compared to the PE-filter because it is made by paper and it’s dissolve in liquid after a short time. Therefore the PE-filter is recommended as the best solution for the micro sampler.

7.2.2 The draw test

The purpose with this test is see how the capillary wire of the micro sampler is filled and

drawn into the blood gas analyzer. 10 pieces of capillary wires with approximated the same

inner diameter as the micro sampler was chosen. The capillary wires were cut to 49 .6 mm

(length of the micro sampler). The bottom and top sides of the capillary wires were closed

by rubber caps. The top rubber cap was cut through by a hand knife, so the probe from the

blood gas analyzer passes. In addition, a magnet was put into the capillary wire to get a

realistic scenario of the test objects. The using procedure of the test is listed in the following:

Press a rubber cap in bottom side;

Put the magnet into the capillary wire;

Press the top cap (cut through) on the top side;

Fill the capillary with blood;

Put the capillary wire on to the blood gas analysis;

Run the sample.

Table 29 The result of the liquid test


123

The tests were performed by Farshid Salehian who is biomedical laboratory technician at Radiometer. The tests were performed on two blood gas analyzers. One was ABL 90 nr.1 and the other was ABL 90 nr.2. The capillary wire was filled with blood first (fig. 132 top to right) and afterward the magnet was inserted and at last the caps were pressed on both sides of the capillary wire. The capillary wire was drawn into the blood gas analyzer (fig.132 bottom right) and it was possible to obtain all the blood gas parameters. But a little rest of blood was still in the capillary wire after it was drawn. This was because an extra volume (10 µL) was set on the target volume in relation to the parts tolerance. Otherwise all the drawn tests were run successfully in the blood gas analyzer and gave all the blood gas parameters. All in all 10 tests objects drawn into the blood gas analyzer.

When the drawn test of the test objects was run, another test with current Radiometer capillary wire was performed in the same way where 10 drawn test run on the blood gas analyzer. The blood gas parameters of the 2 tests were compared with each other in the fig. 133.

Figure 132 Top left: Concept Capillary Wire (CCW) filled with blood. Top right: CCW filled with blood. Bottom left: CCW drawn into to the blood gas analyzer. Bottom right: CCW after drawn from the blood gas analyzer.


124

It is impossible to obtain exactly same blood gas parameters every time from the samples. Approximately 5 % deviation from sample to sample is acceptable when using the same syringe or capillary. It is critical when the deviation is than 15 -20 % from sample to sample using one type of capillary wire or two different types.

Furthermore, the most important blood gas parameters which are oxygen (pO2) and carbon dioxide (pCO2) are compared with each other in the following fig. 134-136. The conclusion of the two tests is that the deviation of the blood gas parameters never exceeds 10 %. The deviation of the blood gas parameters are around 5% for all run tests. An e.g. of that is shown in the fig.133 where two test results are compared. The deviations of blood gas parameters are very small. It is proved by these experimental tests that the concept of micro sampler works just as well as current capillary wire from Radiometer.

Figure 133 Left: Blood gas parameters from concept capillary wire. Right: Blood gas parameter of the Radiometer capillary wire


125

pO2 and pCO2 parameters Average Standard deviation (STD)

pO2 values of Radiometer capillary wire 22,9 1,0

pO2 values of concept capillary wire 24,3 0,72

pCO2 values of Radiometer capillary wire 56,54 0,23

pCO2 values of Concept capillary wire 58,9 0,6 Table 30 STD and average of 5 repeated measurements for the PO2 and PCO2 values for the Radiometer capillary wire and concept capillary wire

19

20

21

22

23

24

25

1 2 3 4 5

PO

2

Tests

Radiometer capillary wire

Concept capillary wire

Figure 134 pO2 values of Radiometer capillary wire and concept capillary wire

54

55

56

57

58

59

60

61

1 2 3 4 5

pC

O2

Samples

Radiometer capillary wire

Concept capillary wire"

Figure 135 pCO2 values of Radiometer capillary wire and concept capillary wire


126

7.2 Usability test on the hospital

The purpose of the usability test is to evaluate the concept design by testing it on the users. To do that a questionnaire is prepared in connection with a concept design sampler and targeted for those who have prior experience with both sampler and needle shield from Radiometer. In the figure below pictures show the concept design product sampler (left) and Needle shield (Right). The concept design are engineered to protect the user from needle injuries and to minimize the risk of contact with blood of the patient.

The test was executed on Herlev hospital in the Intensive-Care Unit (ICU) department on the 28th. of May 2013. The test subjects were 1 ICU nurse and 2 biomedical laboratory technicians who have 5-6 months of experience with the SafePico syringes including needle shield and the vented Tip Caps (VTC) from Radiometer (see fig.138).

Figure 136 Left: Sampler (top cover). Right: Needle shield (bottom cover)

Figure 137 Left: PICO 70 sampler with VTC on. Right: Current needle shield from Radiometer


127

7.2.1 Questionnaire A –Needle shield from Radiometer

1. Have you seen this before? Annette: Yes Helle: Yes Ulla: Yes 2. How long have you used the device? Annette: Since January 2013. Helle: Since January 2013. Ulla: Since January 2013. 3. How often do you use the device per day approximately? Annette: 1-2 times per day. Helle: 1-2 times per day. Ulla: 1-2 times per day.

Name: Helle Christensen


Age: 39

Name:Ulla Jensen


Age: 60

Name:Annette Berit Larsen

Title: ICU Nurse

Age: 42

Figure 138 List of participants


128

4. Why do you use the device? Annette: Artery blood sampling Helle: Artery blood sampling and education (training the other nurses and medical laboratory technicians to use the artery blood samplers). Ulla: Artery blood sampling and education

5. Do you think the device help you?

a) Yes, No, Maybe

Annette: Yes. Helle: Yes. Ulla: Yes.

b) If yes, in which way?

Annette: Avoid stinging my fingers. Helle: It’s safe. Ulla: I feel safe with this devise. 6. Please describe negative aspects of the device. Annette: None Helle: It’s hard to slide forward. Ulla: The diameter size is big and it’s hard to slide forward. 7. Please describe positive aspects of the device. Annette: It is safe and it looks good. Helle: It is safe. Ulla: The device is smart, safe and you can depose needle shield including needle. Furthermore, the needle shield is easy to remove from the syringe.

7.2.2 Questionnaire A –Radiometer sampler with VTC on

The sampler with VTC on is presented for the user and afterwards questions are asked:

1. How long have you used the device? Annette: Since January 2013. Helle: Since January 2013. Ulla: Since January 2013. 2. How often do you use the device per day approximately? Annette: 5-10 times per day. Helle: 1-2 times per day. Ulla: 5-10 times per day. 3. Why do you use the device? Annette: Artery blood sampling. Helle: Artery blood sampling and education. Ulla: Artery blood sampling and education.


129

4. Do you think the device helps you?

a) Yes, No, Maybe Annette: Yes. Helle: Yes. Ulla: Yes.

b) If yes, in which way?

Annette: It gives the correct blood gas parameters. Helle: It is possible to vent the syringe by VTC and thereby correct gas parameters are obtained. Ulla: Easy to use, (I like the syringe and VTC).

5. Please describe negative aspects of the device.

Annette: None. Helle: It is expensive. Ulla: Sometimes it is difficult to vent. It requires education to know how to use the syringe and VTC together.

6. Please describe positive aspects of the device.

Annette: It is easy to use and easy to mix. Helle: It´s possible to vent the sampler so correct parameter results are obtained. It has a good mixing ability and it has a barcode which make it easy for me to identify the patient. Ulla: The device has good grip are area .It is easy to puncture an artery for blood sampling.

7.2.3 Questionnaire C –concept of design sampler

At last the concept of the micro sampler is presented to the user, and afterwards questions linked to usability are asked: 1. Do you think the device will helps you?

a) Yes, No, Maybe

Annette: Yes Helle: Yes. Ulla: Yes.

b) If yes, in which way? Annette: If the functionality works, it will be very easy to use. Helle: It is difficult to obtain big amounts of blood from babies. Therefore it´s nice that the target volume is in 65µL. Ulla: I like the spring function of the slide system. I think it can make my job easier.


130

2. Please describe negative aspects of the device.

Annette: There´s a risk for stinging my fingers when I slide to side. Helle: I am worried about the functionality of the slide system. Ulla: I am worried I`ll will sting my fingers with this one.

3. Please describe positive aspects of the device.

Annette: Easy to use, the micro sampler can be used with one hand. Helle: I like the spring function sliding (hope it will work), less blood waste. it`s nice that the luer cap is on the micro sampler. Ulla: Better than the other capillary wire because it has better grip areas.

4. Has this sampler better usability than the other samplers?

Annette: Yes. Helle: I could be, it looks easy to use but I need to see the real model. Ulla: No, I think that the current samplers of Radiometer have better grip areas.

5. Do you like the design of sampler? Annette: Yes, it looks nice. Helle: Yes, Just as the sampler from Radiometer. Ulla: Yes

6. Will you suggest it to your colleagues/boss in the future?

Annette: Yes. Helle: Yes. Ulla: Yes

7.3 Conclusion

As a first step the current sampler from Radiometer was presented and afterward the micro sampler was also introduced. The users were interviewed separately to avoid interacting with each other. The interviews shown that the users feel safe when they use current needle shield from Radiometer. However, they thought that the usability of the needle shield could be improved. It was difficult to use the needle shield with one hand. Therefore they thought that sampler from Radiometer (PICO 70) with VTC on has a better usability than needle shield. In addition, the user thought the micro sampler was easy to mix and it has good grip areas. The micro sampler got good feedback although it is a prototype. The users thought the micro sampler will help them and they like the spring functionality of the slide system. The users were willing to suggest the micro sampler to their colleagues/boss in the future. Approximately two out of three thought the micro sampler was easier to use than the current sampler from Radiometer. However, they worried whether the slide system will work or not. Besides they were scared they might sting themselves.


131

8 Failure Mode and Effect Analysis (FMEA) In this chapter Failure mode and effect analysis (FMEA) of the micro sampler is performed. FMEA is one of the systematic techniques for failure analysis. It was developed by reliability engineers in the 1950s to study problems that might arise from malfunctions of military systems. FMEA is a strong a reliability study tool to identify failure modes of systems, sub systems, assemblies and components as well as their causes and effects. For each component, the failure modes and their resulting effects on the rest of the system are identified in detail in the FMEA table/worksheet.

There are many levels of variations within such table therefore FMEA is mainly a qualitative analysis. The variations of type of FMEA analysis are listed in the following:

Functional

Design

Process FMEA is a far-sighted tool where single point of failure analysis is a core task in reliability engineering, safety engineering and quality engineering. A good FMEA process can identify potential failure modes based on experience with similar products and processes or based on common physics of failure logic. In this way a systematic group of activities can be performed to:

Recognize and evaluate the potential failures.

Identify actions that could eliminate or reduce potential failures before reaching the customer.

Document the process and capture lessons learned.

Figure 139 The systematic levels structure of FMEA (Danaher, 2012)


132

Furthermore, FMEA is important because the majority of issues (50-80%) have root cause in design. It is much more cost effective to design with a reliability approach and minimize any need for changes after product release (see fig 140).

8.1 The pre-work

The FMEA input and pre-work are list in the following:

Identify the FMEA approach and scope.

Utilize boundary diagrams as needed.

Identify relevant prior history on product/process.

Translate customer requirement into product design specifications or requirements.

Modify ranking criteria to be relevant to your business.

8.1.1 Identify the FMEA approach and scope

The micro sampler is the system function and it is a new design with long series production.

It is important that the micro sampler can be adapted to the blood gas analyzer, so the test

analysis is correct. Furthermore, the waste or leak of blood is chosen as the most critical

factor, because there is a risk of infection. The boundaries for the analysis are listed in the

following:

Interfaces between top cover and luer cap.

Interfaces between top cover and filter.

Interfaces between top cover and rubber caps.

The subsystems of the sampler which are defined as rubber cap and filter, luer cap and luer

interface (in closed position) must have sealed interfaces to avoid leak.

Lastly, the entire interfaces system which is filter, rubber cap and luer cap must be in the

tolerance zone so the part can assemble easily.

Figure 140 Correction Vs. Prevention of FMEA (Danaher, 2012)


133

8.1.2 Utilize boundary diagrams as needed

This section shows the block diagram and the boundary of the system FMEA which are

illustrated in fig 141 and 142.

Micro sampler -system

Packing

system

Filter Rubber

cap Knife cut

Capillary system

End Interface of

capillary wire

Luer interface

Inner interface of

capillary wire

Cap system

Inner interface

of luer cap

System FMEA

Design FMEA Subsystems

Process FMEA Components

Figure 141 Block diagram of micro sampler

Figure 142 Boundary diagram of the micro sampler


134

8.1.3 Identify relevant prior history on product/process

The micro sampler have been identified for relevant prior history for existing parts/product used in design, similar modification of existing components for fits and function in the chapter 1.

8.1.4 Translate customer requirement into product design specifications or requirements

The customer requirement for system, design and process are translated into the product design specifications in the following: System

Micro sampler Must be able to take a blood sample of 85 µL from the arteries. Must be able to draw 65µL into the blood gas analyzers. Must dim the light 50 % from the slot of the queue layer. The sampler must be free of air bobbles and foam.

Sub -system

Packing Subsystem

Rubber cap It must support the influx of the air while the sample is drawn into the blood gas

analyzers. No leaking allowed between rubber and filter interfaces. Filter

The filter must seal when it´s filled with blood.

Capillary subsystem

Capillary wire

The capillary wire inner radius interface must allow a good mixing ability.

No leaking allowed between filter and end of the capillary wire interfaces.

Magnet

There must be an air gap between the inner radius of the capillary wire and the

magnet.

Cap subsystem

No leaking allowed between luer interface and the luer cap.

8.1.5 Modify ranking criteria to be relevant to your business

There are 3 kinds of the ranking criteria which are relevant in the FMEA analyzing process and they are shown in fig 143.

Figure 143 The ranking criteria of FMEA analyzing process (Danaher,2012)


135

Furthermore the 3 ranking criteria are scaled based on Danaher recommendation (see fig 144- 146). A team from Radiometer has decided that the default scale of the severity should be modified to 1-5 instead for 1-10 because the requirement from U.S. Food and Drug Administration (FDA).

Figure 144 Assigning relative weighting to the severity (Danaher, 2012)

Figure 145 Assigning relative weighting to the occurrence of cause (Danaher, 2012)


136

Lastly, the symbol key of the FMEA template is shown in the fig 147, remark that the severity is rescaled by a team of the Radiometer to 1-5 (see the ring marks areas in the fig.147).

Figure 146 Assigning relative weighting to the detection (Danaher, 2012)

Figure 147 Symbol keys of the FMEA template (Danaher, 2012)


137

8.2 FMEA of the micro sampler

The FMEA for system, design and process of the micro sampler are shown in fig.148-150.

Figu

re 1

49

Sys

tem

FM

EA o

f m

icro

sam

ple

r

Figu

re 1

48

De

sign

FM

EA o

f th

e m

icro

sam

ple

r


138

Figu

re 1

50

To

p:P

roce

ss F

MEA

. Bo

tto

m:

Solu

tio

n t

o P

roce

ss F

MEA


139

9. Discussion The optimal concept solution to the micro sampler was found in systematic way in the

concept phase, and it was improved with a usability test (in Radiometer) and design

calculations. But that doesn’t mean that the micro sampler cannot be improved linked to

manufacturing and usability, e.g. it is possible to build a cap function in the bottom cover. The

idea is that the top of the bottom cover can press on the tip of the needle when the bottom

cover slide to closed position. In this way a closed system can be obtained. The cap function

gives the following improvements:

The luer cap of top cover can be neglected.

It is not necessary to have a twist system.

Less operations step.

Less part to dispose.

Easy to use.

However, to obtain the cap function of the bottom cover, it is necessary to have a soft

interface, between the needle tip and the top of the bottom cover. The soft interface can be

produced by:

In 2 –component injection molding where a silicone rubber disc can be molded in the

top of the bottom cover and afterward the bottom cover can be molded.

Assembly the bottom cover with a rubber disc (rubber disc must be placed under the

top of the bottom cover).

A second improvement could be the core of the capillary wire in the top cover mold which

has a big risk for deflection during the injection molding process, because the filling

pressure/pressure at switch-over point is too high. It can be improved by the following:

Add flow-leader into the part.

Several injection points on the part (e.g. 2 points).

Choose a PETG with low viscosity.

The optimal solution is to add a flow-leader between the external diameter of top cover and

the capillary wire. Then the flow length reduces and it works as a supporter to decrease the

stress applied during ejections and the assembly process.

Furthermore, it can be difficult for the tool maker to procedures the integral hinges of the

parts because they have small dimensions. Therefore it can be expected that the shape of the

integral hinges change, e.g. to a circular. Alternatively the dimensions of the integral hinges

can be increased.

Lastly, according to the mold flow simulation the dimensions of the parts are inside the GPS

specification. But it is only in theory therefore it can be difficult for the real measurement

points to comply with GPS specification. Therefore it can be expected that some of the

tolerances will need to be increased.


140

10. Conclusion The primary goal with this project has been to design a micro sampler without a plunger

based on previous generation of samplers (type Pico 70 including VTC). Focus on designing a

micro sampler which was able to draw a small amount of blood from the arterial blood

vessels. It can be concluded linked to the experimental and theoretical work that the primary

goal is achieved. A number of key conclusion points have been achieved during this project

and are listed in the following:

Theoretical work:

A perfect micro sample is achieved not when there is nothing more to add, but when

there is nothing more to take away.

In general semi-crystalline materials have lower creep rates than amorphous

materials. On the other hand the amorphous materials have low shrinkage

compared to semi-crystalline materials.

It is important to use a very fine mesh with the correct mesh tolerance to obtain a

good mesh for simulating the parts in the mold flow simulation.

The silicone rubber cap must have PVDF coating to prevent volume change of pO2

and CO2 during 30 min storage.

The chosen material (PETG) for the capillary wire must have a corona or plasma

treatment, so the surfaces obtain a higher surface tension to draw blood from the

patient.

No manufactured or molded objects have a perfect geometry which can be achieved

in reality. But with using the GPS tolerancing, with large number of measurement

points, it is possible to give a realistic picture of the geometry of an object.

The GPS can give a detailed description of geometrical features linked to functional

properties. E.g. a circle diameter which can be defined in several ways.

Using a good FMEA process reduces or eliminates failures.

Experimental work:

It is important to involve the users in product development, because they give direct

input on how real users use the product. In this way optimized products are achieved

and thereby lower product cost is achieved.

The micro glass filter is a bad solution for the micro sampler, because it has poor

resistant to liquid. In addition the micro glass filter compressed easily because it is

soft and the flow through the filter decreases.

The chosen PE-filter can stand more than 5 bars pressure for 3.5 s without leaking.

The inner diameter of the capillary must be 50 % higher than the diameter of the

probe, and then the capillary wire can be drawn into the blood gas analyzer.

Otherwise there is a risk for blood waste when the probe runs into the capillary wire.

It is possible to draw the micro sampler into the blood gas analyzer while the end of

the capillary wire is closed by rubber cap (no air flux).

To obtain the best mixing ability of the micro sampler, the length of the micro

sampler must be less than 55 mm.


141

11. Outlook A lot of experimental tests of the micro sampler are usually performed to show the

functionality and flow capacity of the filter, its mixing ability and how the blood is drawn into

the blood gas analyzer (ABL 90). Hence, the micro sampler still misses a lot of experimental

tests to confirm that the sampler works. The relevant tests are listed in the following:

Real time stability test –The purpose of the test is to evaluate the performance of

micro sampler during a real time stability test. The test is performed to meet the

requirement of ISO 11607-1:2009[1]. The test includes three independent lots

following validation of the production process and sterilization from manufacturer.

The stability test includes also storage of the micro sampler under temperature and

humidity controlled conditions, sampling and analysis.

Design test – The performance of the integral hinges of the parts must be tested for

functionality (in real using). Furthermore the performance of press fits for rubber

and luer cap must be tested with pulling test.

Sampling test –The performance of the micro sampler which consists of filter,

rubber cap and capillary wire must be tested for artery blood sample from a patient.

ABL900 test –The micro sampler must be tested on the ABL 900 (beacon) to evaluate

the performance of how it’s drawn into the beacon from the queue layer.

Furthermore the micro sampler is able to work with other needle shields which are already

on the market, e.g. the needle shield from Smiths Medical or Monoject Magellan shown in

the figure below. In the future Radiometer coved choose to invest in the new needle shield

(bottom cover) or buy the needle shield from a supplier. In relation to that it is necessary to

study the following:

Advantages and disadvantages of investing in the new needle shield.

Advantages and disadvantages of investing in buying the needle shield from a

supplier.

Market analysis and cost calculations of the products.

Usability test of the products.

Performance test of the functionality.

Result analysis of this study.

Figure 151 Left needle shield from Smiths Medical. Right needle shield from Monoject Mangellan


142

12. References

Chapter 2:

Nigel Cross, Engineering Design Methods Strategies for Product Design, fourd

edition, Wiley, p.139-161.

Peder klidt, Morgens Myrup, Produktudvikling: Kompendium til kurset 41541 fra

ide til produkt, Technical University of Denmark, DEL 4 p. 2-32.

Chapter 3:

Dominick Vincent Rosato, Donald Vincent Rosato, Marlene G.. Rosato, Injection molding handbook, Kluwer academic publishers, Springer, 2000, chapter 6 molding material p.479 -507.

Allan B. Rasmussen, Bjarne Jensen, Claus Roth Nielsen, Jens Johansen, Kjeld Karbæk, Peter Kjærsgård and Tommy B. Rasmussen: Plastteknologi p.67-95.

Guido Tosello: Design of plastic products (slide from course design of plastic part, lecture 5 and 6).

Cyclic Olefi n Copolymer (COC)-Topas Published in March 2006,P.1-17.

Chemical structure and psysical properties of Cyclic of olefin copolymers ( IUPAC Technical Report) Prepared for publication by Ju Young shin, Ji Yong Park, Chenyang Liu, Jiadsong He and Sung Chul Kim. P.812.

Lekhraj Ghai, Polyethylene Naphthalate —A new-generation, high-performance polymer p.1-3

Topas Advanced Polymers GmbH, datasheet, Published in 30.08.2006, p.1

Typical Engineering Properties of Polypropylene, INEOS, Feb.2010, p.1-2

Chapter 4:

Henrik. Olesen, Knud Kjeldsen og Inge Ibsen. Klinisk – kemisk kompendium

F.A.D.L.s forlag, 1979 p.570.

Petrophysics MSc Course Notes -Fluid Saturation and Capillary Pressure p.39-42.

Dr.-Ing. Gunter Erhard, Designing With Plastics 2006, HANSER, p.345-362.

John P. Beaumont, Penn State Erie, The behrend College, Erie Pennsylvania Runner

and Gating Design Handbook: Tools for Successful Injection Molding, HANSER, 2nd

edition, 2007, p.160-179.


143

Dominick Vincent Rosato, Donald Vincent Rosato, Marlene G.. Rosato, Injection molding handbook, Kluwer academic publishers, Springer, 2000, chapter 6 molding material p.115 -125.

Viggo Tværgaard, Niels Olhoff,Ann Bettina Richelsen, Arne Guldmann Nielsen

Dimensionering og styrke, Technical University of Denmark, spring 2009, p. 9-20,

p.118-119 and p.212-213.

Henrik Koblitz Rasmussen Compendium in Polymer processing, Technical University

of Denmark, p.8-20 and p.38-43.

Material data center: Datasheet of Easter -PETG and PP.

DMS engineering plastics, Technical guide, p.1.

Synventive molding solution, Hot Runner Guide layout and design from, p.17-21.

R. A. Malloy, Plastic part design for injection molding: an introduction, HANSER, 1994, p.15 and p 85-108.

Nigel Mills, Plastic microstructure and engineering applications, Elsevier, third

edition, p-322-330.

Chapter 5:

Dominick Vincent Rosato, Donald Vincent Rosato, Marlene G.. Rosato, Injection molding handbook, Kluwer academic publishers, Springer, 2000, p.151 -181.

Allan B. Rasmussen, Bjarne Jensen, Claus Roth Nielsen, Jens Johansen, Kjeld Karbæk, Peter Kjærsgård and Tommy B. Rasmussen: Plastteknologi p.234-242.

Guido Tosello: slide from course design of plastic part, Technical University of Denmark, lecture 1 and 2

Chapter 6:

Leonardo De Chiffre, Geometrical metrology and machine testing, Technical University of Denmark, 2011 p. 63-70.

Henrik Strøbæk Nielsen, GPS bogen, Erhvervsskolernes forlag, 2010 p.81-148.

Bennich P. Nielsen, H.S (2005). An overview of GPS. Institute for Geometrical product Speficication.

ISO/DS 812: 1995 Plastic moldings –Tolerances and acceptance conditions


144

ISO/TR- 14253-1 :1998 Geometrical Product Specification (GPS)- Inspection by measurement of workpieces and measurement equipment -Part 1: Decision rules for proving conformance or non-conformance with specifications.

ISO/TR- 14638: 1995 Geometrical Product Specification (GPS)-Masterplan.

ISO/TR- 14659: 1998 Geometrical Product Specification (GPS)-Fundamentals Concept principles and rules.

ISO/TR- 14660: Geometrical Product Specification (GPS)-Geometrical features –general term and definition.

Chapter 8: Danaher, slides training FMEA, 2012.

D. H. Stamatis, Failure Mode and Effect Analysis: Fmea from Theory to Execution, 2nd edition, 2003,p.22-40 and p.68-76.

Documents

Design and prototype of a capillary blood sampler at Radiometer … · Radiometer is a global provider of high technological solutions for acute care diagnostics in blood gas testing,