i

OPTIMIZATION OF MOLDING PARAMETER EFFECT TO WARPAGE AND

SHRINKAGE BASED ON PLASTIC FLOW SIMULATION SOFTWARE: HAND

PHONE CASING

MOHD NORHAFIZI BIN ROHAIZAT

A report submitted in partial fulfilment of

The requirements for the award of the degree of

Bachelor of Mechanical Engineering with Manufacturing

Faculty of Mechanical Engineering

UNIVERSITI MALAYSIA PAHANG

DECEMBER 2010

ii

UNIVERSITI MALAYSIA PAHANG

FACULTY OF MECHANICAL ENGINEERING

We certify that the project entitled “Optimization of Molding Parameter Effect to Warpage

and shrinkage based on Plastic Flow Simulation Software: Hand Phone Casing” is written

by Mohd Norhafizi Bin Rohaizat. We have examined the final copy of this project and in

our opinion; it is fully adequate in terms of scope and quality for the award of the degree of

Bachelor of Engineering. We herewith recommend that it be accepted in partial fulfilment

of the requirements for the degree of Bachelor of Mechanical Engineering with

Manufacturing Engineering.

Examiner Signature

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SUPERVISOR’S DECLARATION

I hereby declare that I have checked this project and in my opinion, this project is adequate

in terms of scope and quality for the award of the degree of Bachelor of Mechanical

Engineering with Manufacturing Engineering.

Signature : ..................................

Name of Supervisor : Mr Mohd Reza Zalani Bin Mohd Suffian

Position : Lecturer Faculty of Mechanical

Engineering Universiti Malaysia Pahang

Date : .................................

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STUDENT’S DECLARATION

I hereby declare that the work in this project is my own except for quotations and

summaries which have been duly acknowledged. The project has not been accepted for any

degree and is not concurrently submitted for award of other degree.

Signature : ................................

Name : MOHD NORHAFIZI BIN ROHAIZAT

ID Number: ME07036

Date : ...............................

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ACKNOWLEDGEMENTS

First of all, thanks to ALLAH SWT for giving me the strength and the chances in

completing this first Final Year Project. In preparing this thesis, I was in contact with many

people, researchers, academicians, and practitioners. They have contributed towards my

understanding and thoughts.

In particular, I wish to express my sincere appreciation to my previous thesis

supervisor, Mrs Siti Haryani Binti Tomadi for her encouragement, guidance, critics and

friendship in order to finish my final year project. I am also very thankful to all lecturers in

Faculty of Mechanical Engineering for their guidance, advices and motivation. The credit

also goes to all lecturers, tutors, teaching engineers (JP) especially Mr Imran and assistant

teaching engineers (PJP), Mr Faizul for helping me. Without their continued support and

interest, this thesis would not have been the same as presented here.

I am also indebted to Universiti Malaysia Pahang for funding my degree study. My

coursemates should also be recognized for their support. My sincere appreciation also

extends to all my colleagues and others who have provided assistance at various occasions.

Their views and tips are useful indeed. Unfortunately, it is not possible to list all of them in

this limited space. I am grateful to all my family members.

Finally, I would like to thanks my family especially my parent for their constant

support, encouragement and understanding during my studies.

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ABSTRACT

Injection molding is a manufacturing process for producing part for both thermoplastic and

thermosetting plastic material. Objective of this project to determine the parameter effect to

the warpage and shrinkage of the handphone casing and to determine the optimization

parameter for reduce the warpage and shrinkage. For this project 3D scanner are use to scan

the hand phone casing to get the parameter and analyse with MoldFlow simulation software

to optimize the effect to warpage and shrinkage. Shrinkage and warpage tendencies in

molded parts,are influenced by actions taken in each and all of the manufacturing stages of

part design, material selection, tool design, and processing. The mold temperature(MT),

packing time (Pt), packing pressure (PP) and cooling time (Ct) in the packing stage are

considered as machining parameters. As increase in mold temperature (MT), the shrinkage

also increase and as increase in cooling time (Ct), the shrinkage decrease. Other than that,

as increase the packing pressure (PP), the shrinkage usually decrease.

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ABSTRAK

Pembentukan suntikan adalah proses pembuatan untuk menghasilkan bahagian untuk

kedua-dua bahan plastik termoplastik dan termoset. Tujuan projek ini untuk mengetahui

pengaruh parameter pada melenting dan penyusutan selongsong telefon bimbit dan juga

untuk menentukan parameter yang optimum untuk mengurangkan melenting dan susut.

Dalam projek ini, 3D scanner yang digunakan untuk mengimbas solongsong telefon bimbit

untuk mendapatkan parameter dan dianalisis dengan perisian simulasi MoldFlow untuk

mengoptimumkan kesan untuk melenting dan susut. Susut dan kecenderungan melenting di

bahagian dibentuk, dipengaruhi oleh tindakan yang diambil dalam mana-mana dan semua

tahap pembuatan desain bahagian, pemilihan material, rekaan alat, dan pemprosesan. Suhu

acuan (MT), masa padatan (Pt), tekanan padatan (PP) dan masa pendinginan (Ct) dalam

tahap kemasan dianggap sebagai parameter pemesinan. Seperti kenaikan suhu acuan (MT),

susut juga meningkat dan peningkatan masa pendinginan (Ct), susut juga menurun. Selain

itu, seperti peningkatan tekanan padatan (PP), susut biasanya menurun.

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TABLE OF CONTENTS

Page

TITLE i

APPROVAL DOCUMENT ii

SUPERVISOR’S DECLARATION iii

EXAMINER’S DECLARATION iv

STUDENT’S DECLARATION v

DEDICATION vi

ACKNOWLEDGEMENTS vii

ABSTRACT viii

ABSTRAK ix

TABLE OF CONTENTS x

LIST OF TABLE xiii

LIST OF FIGURE xiv

CHAPTER 1 INTRODUCTION

1.1 Project Background 1

1.2 Project Title 2

1.3 Objective 2

1.4 Problem Statements 2

1.5 Scope of Project 3

CHAPTER 2 LITERATURE REVIEW

2.1 Introduction 5

2.2 Injection Molding 6

2.3 Warpage 9

2.4 Shrinkage 10

2.5 Parameter 12

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2.5.1 Injection Time 14

2.5.2 Mold Temperature 14

2.5.3 Packing Time 14

2.5.4 Packing Pressure 15

2.5.5 Melt Temperature 15

2.5.6 Cooling Time 16

2.6 MoldFlow Simulation Software 16

2.7 SolidWorks 19

2.8 3D scanner 20

2.9 Conclusion 22

CHAPTER 3 METHODOLOGY

3.1 Introduction 24

3.2 Flow Chart 25

3.3 Decide Objective and Scope of Project 26

3.4 Literature 26

3.5 3D Modelling Of Hand Phone Casing Using 3D Scanners 27

3.6 Generation of Hand Phone Casing 34

3.7 Dimension Obtain For Solidwork 34

3.8 Analysis Using Moldflow Simulation Software 34

3.9 Generation of New Molding Parameter 35

3.10 Analysis 35

3.11 Documentation & Presentation 36

3.12 Conclusion 36

CHAPTER 4 RESULTS & DISCUSSION

4.1 Introduction 37

4.2 Material Selection 37

4.3 Result 39

4.3.1 Result for Top Hand Phone Casing 39

4.3.1.1 Mold Temperature 39

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4.3.1.2 Melt Temperature 41

4.3.1.3 Injection Pressure 43

4.3.1.4 Cooling Time 45

4.3.2 Result for Bottom Hand Phone Casing 47

4.3.2.1 Mold Temperature 47

4.3.2.2 Melt Temperature 49

4.3.2.3 Injection Pressure 51

4.3.2.4 Cooling Time 53

4.4 Discussion 55

4.4.1 Mold Temperature 55

4.4.2 Melt Temperature 55

4.4.3 Injection Pressure 55

4.4.4 Cooling Time 56

CHAPTER 5 CONCLUSIONS & RECOMMENDATION

5.1 Introduction 57

5.2 Conclusion 57

5.3 Recommendation 58

REFERENCES 61

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LIST OF TABLES

Table No. Title Page

4.1 Properties to Analyze Mold Temperature Parameters 38

4.2 Properties to Analyze Melt Temperature Parameters 38

4.3 Properties to Analyze Injection Pressure Parameters 39

4.4 Properties to Analyze Cooling Time Parameters 39

4.5 Result Warpage and Shrinkage for Mold Temperature 41

4.6 Result Warpage and Shrinkage for Melt Temperature 42

4.7 Result Warpage and Shrinkage for Injection Pressure 44

4.8

4.9

4.10

4.11

4.12

Result Warpage and Shrinkage for Cooling Time

Result Warpage and Shrinkage for Mold Temperature

Result Warpage and Shrinkage for Melt Temperature

Result Warpage and Shrinkage for Injection Pressure

Result Warpage and Shrinkage for Cooling Time

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xiv

LIST OF FIGURES

Figure No. Title Page

2.2.1 The injection major part 6

2.2.2 The injection molding major part (front view) 7

2.4.1 The pvT curves for amorphous and crystalline polymers 11

2.4.2 Processing and design parameters that affect part shrinkage 12

2.6.1 Example of warp analysis 16

2.6.2 Preview of moldflow Simulation Software 17

2.8.1 3D scanner 20

3.5.1

3.5.2

3.5.3

3.5.4

3.5.5

3.5.6

3.5.7

3.5.8

3.5.9

3.5.10

3.5.11

3.5.12

3.7.1

Image from 3d Scanner for Front Cover Top

Image from 3d Scanner for Front Cover Bottom

Image from 3d Scanner for Back Cover Top

Image from 3d Scanner for Back Cover Bottom

Image from 3d Scanner for Front Cover Top

Image from 3d Scanner for Front Cover Bottom

Image from 3d Scanner for Back Cover Top

Image from 3d Scanner for Back Cover bottom

Image from 3d Scanner for Front Cover after Merge

Image from 3d Scanner for Back Cover after Merge

Image from 3d Scanner for Back Cover after Edit

Image from 3d Scanner for Back Cover after Edit

Solidwork Drawing Bottom Hand Phone Casing

27

27

28

28

29

29

30

30

31

31

32

32

33

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3.7.2 Solidwork Drawing Top Hand Phone Casing 34

4.1.1 Warpage at Mold Temperature Is 60°C 40

4.1.2 Shrinkage at Mold Temperature Is 60°C 40

4.1.3 Warpage at Melt Temperature Is 205°C 41

4.1.4 Shrinkage at Melt Temperature Is 205°C 41

4.1.5 Warpage at Injection Pressure Is 120 MPa 43

4.1.6 Shrinkage at Injection Pressure Is 120 MPa 44

4.1.7

4.1.8

4.1.9

4.1.10

4.1.11

4.1.12

4.1.13

4.1.14

4.1.15

4.1.16

Warpage at Cooling Time is 20s

Shrinkage at Cooling Time is 20s

Warpage at Mold Temperature Is 60°C

Shrinkage at Mold Temperature Is 60°C

Warpage at Melt Temperature Is 205°C

Shrinkage at Melt Temperature Is 205°C

Warpage at Injection Pressure Is 120 MPa

Shrinkage at Injection Pressure Is 120 MPa

Warpage at Cooling Time is 20s

Shrinkage at Cooling Time is 20s

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CHAPTER 1

INTRODUCTION

1.1 Project Background

Injection molding is a very mature technology, but the growth of layer-build,

additive, manufacturing technologies has the potential of expanding injection molding into

areas not commercially feasible with traditional molds and molding technique. What is

missing is the fundamental understanding of how the modifications to the mold material

and mold manufacturing process impact both the mold design and the injection molding

process. Plastic injection processes comprise plastication, injection, packing, cooling,

ejection and process/part quality control applications. These steps are followed for the

parts, which are designed to be produced by plastic injection method.

There are many factors affecting warpage and shrinkage. These are mold

temperature, melt temperature, packing pressure, packing time, cooling time, injection

velocity, injection time, injection pressure, gate location, runner type, etc. The warpage and

shrinkage is reduced further by optimizing the six significant process variables: injection

time, post fill (cooling plus packing) time, packing time, packing pressure, melt

temperature, and coolant temperature. Computer-aided analysis and engineering software

are used in order to minimum the warpage. For plastic injection process, one of the

commercial computer-aided engineering software is the MoldFlow. In this study,

MoldFlow simulation software is used to make the analysis and optimize the parameter

effect to the warpage and shrinkage.

2

1.2 Project Title

Optimization of Molding Parameter Effect to Warpage and shrinkage based on

Plastic Flow Simulation Software: Hand Phone Casing

1.3 Objective

1. To define the molding parameter in injection molding of hand phone casing.

2. To determine parameter effect in molding parameter to warpage and shrinkage of hand

phone casing.

3. To optimize the molding parameter and minimize the warpage and shrinkage of hand

phone casing based on Plastic Flow simulation software.

1.4 Problem Statements

In this project, warpage and shrinkage are depends on so many factors and one of it

is the injection molding parameter. The parameter includes mold temperature, melt

temperature, injection time, packing pressure, packing time, and so on. 4 parameters were

chosen to make the analysis in order to make the optimization of molding parameter and

minimize the warpage and shrinkage of hand phone casing. The parameters include mold

temperature, melt temperature, injection pressure and cooling time.

The parameters are used to make analysis base on plastic flow simulation software.

In this project, MoldFlow Plastic Insight was use to make the analysis on the chosen

parameter. The analysis includes warpage and shrinkage in hand phone casing to optimize

the parameters that affect the both defect.

3

1.5 Scope of Project

Obtain the data and all the information for the title to understand this project by do a

lot of research that come from many sources such as internet, books, journals, articles and

many more. In other to make more understand on this project, the guidance from the

supervisor is important. Also, to check the progress is going smoothly by make sure that the

data and information that obtain from the source are really useful for this project. Meeting

with supervisor is needed in every week until this project is done.

3D scanning is used in this project also referred as 3D digitizing. This device is

utilization of a three dimensional data acquisition device to acquire a multitude of X, Y, Z

coordinates on the surface of a physical object or object’s shape and appearance include

points. The scanner then uses these points to form a 3D digital model of the part. This

captured data is typically stored as a list of xyz-coordinates in a point cloud file. 3D

scanners can be categorized as contact (CMM arms) or non-contact (white light, 3D laser

scanners, or stereo-vision based). Some can even capture internal features.

After getting the shape of the object from the 3D scanning, then the data is

transferred into CAD software that known as SolidWorks. SolidWorks is software that uses

to utilize a parametric feature-based approach to create models and assemblies. Parameters

refer to constraints whose values determine the shape or geometry of the model or

assembly. The data is transferred into the SolidWorks because to get the parameters of the

objects that will use in further analysis.

Plastic Flow simulation software then will be used to make the analysis to the

parameter of the object. SolidWorks Flow Simulation is a Computational Fluid Dynamics

(CFD) product for SolidWorks users. It is embedded inside SolidWorks and can perform

fluid flow and heat transfer analysis for some types of fluids (liquids, gases, Non

Newtonian fluids, Compressible liquid. Other than that, it’s a sophisticated practice that’s

gaining popularity. It helps identify a variety of potential problems and improvements for a

4

mold before it gets built. With this software, analysis about this project can be done also get

result to optimize the molding parameter and reduce the warpage and shrinkage.

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CHAPTER 2

LITERATURE REVIEW

2.1 Introductions

This project title is optimization of molding parameter effect to warpage and

shrinkage based on plastic flow simulation software. Optimization means to make

something as good as possible. In this case, optimization of molding parameter is to make

improvement about the molding parameter that effect to warpage and shrinkage in injection

molding.

Plastic injection processes comprise plastication, injection, packing, cooling,

ejection and process/part quality control applications. These steps are followed for the

parts, which are designed to be produced by plastic injection method. Having initial

knowledge about the process that will be undertaken is necessary because of present-day

competitive conditions that force us to produce faster and cheaper with a higher quality,

such as minimum warpage, sink marks, etc. Computer-aided analysis and engineering

software are used in order to meet this necessity.

In plastic injection process, there is one the commercial computer-aided engineering

software’s is the MoldFlow Plastic Insight. In this study, process parameters such as mold

temperature, melt temperature, packing pressure, packing time, cooling time, runner type

and gate location are considered as parameter variables in order to minimize the warpage

and shrinkage.

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2.2 Injection Molding

Injection molding is one of the most common processing methods for

thermoplastics. Nowadays one sees a multitude of different types of injection molded

products in homes, vehicles, offices and factories. These include combs, syringes, paint

brush handles, crash helmets, telephones, soft drink glasses, gearwheels, brief cases,

television housings, typewriters—the list is almost endless.

In the injection molding process, a thermoplastic in the form of granules or powder,

passes from a feed hopper into a barrel where it is heated until it becomes soft. It is then

forced through a nozzle into a relatively cold mold which is clamped tightly closed. After

the plastic is cooled and solidified, the article is ejected and the cycle is repeated. The major

advantages of the process includes its versatility in molding a wide range of products, the

ease with which automation can be introduced, the possibility of high production rates and

the manufacture of articles with close tolerances (R.J. Crawford,1989).

Figure 2.21: The injection major part

Adapted from:

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Figure 2.22: The injection molding major part (front view)

Adapted from:

Injection molding is one of the most important polymer processing methods for

producing plastic parts (H.T. Paro, C.P. Bosnyak, K. Sehanobish, 1986). Process

parameters in addition to molding material and part design are major factors affecting the

quality of plastic parts produced by injection molding. Quality of these parts is often

associated with warpage. Effects of process parameters on non-uniform shrinkage leading

to warpage are investigated from several aspects in literature (A.I. Isayav, Marcel Dekker,

1987).

The injection molding process was first designed in the 1930s and was originally

based on metal die casting designs. Injection molding offers many advantages to alternative

manufacturing methods, including minimal losses from scrap (since scrap pieces can be

melted and recycled), and minimal finishing requirements. Injection molding differs from

metal die casting in that molten metal’s can simply be poured; plastic resins must be

injected with force.

8

The process uses large injection molding machines, which advance the resins

through six major processes to produce everything. Although an injection molding machine

is a complex piece of equipment, it consists of two basic elements, the injection unit and

the clamping unit.

The process starts with a mold, which is clamped under pressure to accommodate

the injection and cooling process. Then, pelletized resins are fed into the machine, followed

by the appropriate colorants. The resins then fall into an injection barrel, where they are

heated to a melting point, and then injected into the mold through either a screw or

ramming device.

Then comes the dwelling phase, in which the molten plastics are contained within

the mold, and hydraulic or mechanical pressure is applied to make sure all of the cavities

within the mold are filled. The plastics are then allowed to cool within the mold, which is

then opened by separating the two halves of the mold. In the final step, the plastic part is

ejected from the mold with ejecting pins. The completed part may contain extraneous bits

called runners, which are trimmed off and recycled. The entire process is cyclical, with

cycle times ranging from between ten and 100 seconds, depending on the required cooling

time.

The injection molding process requires some complex calculations. Every different

type of resin has a shrinkage value that must be factored in, and the mold must compensate

for it. If this value is not precisely determined, the final product will be incorrectly sized or

may contain flaws. Typically, this is compensated for by first filling the mold with resin,

holding it under pressure, and then adding more resin to compensate for contraction. Other

complications may include burned parts resulting from the melt temperature being set too

high, warpage resulting from an uneven surface temperature, or incomplete filling due to a

too slow of an injection stroke.

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2.3 Warpage

Warpage is a distortion where the surfaces of the molded part do not follow the

intended shape of the design. Part warpage results from molded-in residual stresses, which,

in turn, is caused by differential shrinkage of material in the molded part. If the shrinkage

throughout the part is uniform, the molding will not deform or warp, it simply becomes

smaller. However, achieving low and uniform shrinkage is a complicated task due to the

presence and interaction of many factors such as molecular and fiber orientations, mold

cooling, part and mold designs, and process conditions (Kurtaran, H. Kurtaran, B. Ozcelik,

T. Erzurumlu, 2005 ; Dong, B.B. Dong, C.Y. Shen, C.T. Liu, 2005).

.

Warpage in molded parts results from differential shrinkage. Variation in shrinkage

can be caused by molecular and fiber orientation, temperature variations within the molded

part, and by variable packing, such as over-packing at gates and under-packing at remote

locations, or different pressure levels as material solidifies across the part thickness.

Thicker part sections have limited cooling available and cool more slowly than their

thinner or better cooled counterparts. Ribs, bosses, corners, differential mold temperatures,

etc., all contribute to variations in cooling time and rate of cooling. In the mold, a part

develops a differential temperature profile. When the part is ejected, the thicker sections

are still cooling while thinner sections may have reached their final temperature. As the

part cools further the thicker areas, which are no longer restrained, contract and possibly

cause warpage.

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Other causes:

• Warping can also be caused due to non-uniform mold temperatures or cooling rates.

• Non-uniform packing or pressure in the mold.

• Alignment of polymer molecules and fiber reinforcing strands during the mold fill

results in preferential properties in the part.

• Molding process conditions--too high an injection pressure or temperature or improper

temperature and cooling of the mold cavity.

2.4 Shrinkage

The shrinkage of molded plastic parts can be as much as 20 percent by volume,

when measured at the processing temperature and the ambient temperature. Crystalline and

semi-crystalline materials are particularly prone to thermal shrinkage; amorphous materials

tend to shrink less. When crystalline materials are cooled below their transition

temperature, the molecules arrange themselves in a more orderly way, forming crystallites.

On the other hand, the microstructure of amorphous materials does not change with the

phase change. This difference leads to crystalline and semi-crystalline materials having a

greater difference in specific volume ( ) between their melt phase and solid (crystalline)

phase. This is illustrated in Figure 2.41 below. Cooling rate also affects the fast-cooling

pvT behavior of crystalline and semi-crystalline materials (Kurtaran , H. Kurtaran, B.

Ozcelik, T. Erzurumlu, 2005; Dong, B.B. Dong, C.Y. Shen, C.T. Liu, 2005).

11

FIGURE 2.41: The pvT curves for amorphous and crystalline polymers and the specific

volume variation ( ) between the processing state (point A) and the state at room

temperature and atmospheric pressure (point B). Note that the specific volume decreases as

the pressure increases.

Adapted from:

Causes of excessive part shrinkage Excessive shrinkage, beyond the acceptable

level, can be caused by the following factors. The relationship of shrinkage to several

processing parameters and part thickness is schematically plotted in Figure 2.

• low injection pressure

• short pack-hold time or cooling time

• high melt temperature

• high mold temperature

• Low holding pressure.

Problems caused by part shrinkage Uncompensated volumetric contraction leads to

either sink marks or voids in the molding interior. Controlling part shrinkage is important in

part, mold, and process designs, particularly in applications requiring tight tolerances.

Shrinkage that leads to sink marks or voids can be reduced or eliminated by packing the