University of DelawareDecember 10, 2007

Senior Design Team 15

Anthony Brazen IVNick HirannetSam Holland

Megan Keenan

To improve the robustness and reliability of the tablet feeding process.◦ This can be done through prevention and

detection

The tablets are moved along the tracks with the aid of a linear vibrator creating backpressure

The tablets drop through the holes and chutes into the flex

Sensors are currently placed at the top of the chute to detect that a tablet has fallen

What?◦ A flex does not receive a tablet◦ Entire lot must be opened and inspected

Happens 45 out of 8 million tablet drops

Why? Tablet breaks top sensor and may get

stuck in the chute◦ Tablet bounces off side walls causing delayed

drop◦ Tablet never exits the chute

Possibility for erroneous test result Loss of time and money due to product re-inspection

◦ Hand inspection is currently used to ensure that the correct amount of tablets are in each flex Expensive Time consuming

•The tablets exit the chute at a 90 degree angle from entrance into chute•The drastic turn could cause the tablet to hit the side walls, delaying exit from the chute

Top 10 WantsFinal

RankingWants Rate of

Importance

1 Quality control 37

2 Reliability 18

3 Robustness 15

4 Ease of Integration 13

5 Justifiable Cost 9

ConstraintsConstraints

Size

Cleanable

Removable

Compatibility

Prevention Detection

Too many modifications to the chute would cause Siemens to redesign the entire process◦ Too expensive and time consuming

New Feature: Add sensors to the bottom of the chute◦ Sensor detection in current process is placed at

the top, which provides knowledge of the tablet entry, but problem arises upon tablet exitMetrics Performance Value

Process Time >= 1.1 tablets per second

Impact <= a one second greater process time

Cost Less than $60,000 for one working line

Holes will be drilled into the sides of the chutes and the lowest point where the chutes and Lexan meetTwelve sets of visual sensors will be attached to the bottom surface of the Lexan guard Will utilize same communication software that Siemens currently uses

Met with Keyence Sales Rep.4 sensors were ordered Two were able to be eliminated immediately based on visual inspection

FU-12 and FU-51TZThe FU-50 and FU-59 were tested

Test station set-up

Diameter of ALL tablets = 0.2185 in.Large tablet height = 0.1510 in.Small tablet height = 0.0835 in.Red = Strength of beamGreen = Threshold setting

•FU-50 worked well for large tablets, but was quickly eliminated after missing several small tablets in the first two trials

•Due to large beam aperture, which causes a decrease in sensitivity

2000 tablets were dropped Eight trials of 250 tablets were tested ALL tablets were detected

SMALL TabletsLARGE Tablets

Diameter of ALL tablets = 0.2185 in.Large tablet height = 0.1510 in.Small tablet height = 0.0835 in.Red = Strength of beamGreen = Threshold setting

Diameter of ALL tablets = 0.2185 in.Large tablet height = 0.1510 in.Small tablet height = 0.0835 in.Red = Strength of beamGreen = Threshold setting

4 modes of failure for detection have been identified◦ 2 create undesirable risk levels

Sensor gets blocked by an object Sensor becomes unaligned

◦ Both potential effects are that sensor detects a non-existent tablet

◦ HMI and PLC controls will identify a blocked beam or misalignment

Cutting an existing tablet track and adding a 90° turn

• Desired chute drops tablets straight down•Eliminates current chute

2 ways to achieve this• 2- 45° straight angle turn• Curved radius turn

Current StateDesired State

Metrics Performance ValueProbability of Error 0 Errors for 250 Tablets

Impact <= a one second greater process time

TimeLess than 2 mins configuration time

on chute change

CostLess than $60,000 for one working

line

2 aluminum tracks were milled Tracks were mounted on linear vibrator

◦ Test to determine what prototype allows: Tablets to reach the end of the track Tablets get to end of track fastest

VibrationVibration

Tracks without flipper mechanism

• Radius Track has ability

to move tablets faster

• Current system rate =

1.1 tablets/sec

•Both new designs

exceed this rate

•Angle track moved Large

tablets faster

If Siemens decides to replace their current tracks with our 45 degree turned tracks◦ May not allow required space for vacuum

mechanism Alternative to vacuum – flipper mechanism

Full circle rotation

Half rotation

Aluminum cylindrical flipper placed at end of track◦ Six slots cut along the cylinder to receive tablets

from track◦ Upon loading, cylinder will rotate CW allowing

tablets to be released

Cost Justification: 1 bad flex = $25,000 in lost productivity, re-packaging,and labor• 10 bad lots per year = $250,000• Detection at the bottom of chute pays for itself

Metrics Performance Value Achieved Value

Process Time >= 1.1 tablets per second up to 3.5 tablets per second

Impact Does not perform slower than current system Up to 350% Faster

Cost Less than $60,000 for one working line $18,353.84

Detection

Metrics Performance Value Achieved Value

Probability of Error 0 Errors for 250 Tablets 0 Errors for 2000 Tablets

Impact Does not slow down current system by > 1 sec No extra process time

Time Less than 2 mins configuration time on chute change Automated on Computer

Cost Less than $60,000 for one working line $12,840

Tracks

0 defects in a sample of 250 tablets is considered acceptable by Siemens statistical analysis◦ We tested 8 samples of 250 tablets to validate

this acceptance

The number of samples (n) to be taken can be calculated by the following expression:

Z(A) = standard normal variant value for error Z(B) = standard normal variant value for β error = AQL (Average Quality Level) = LTPD (Lot Tolerance Percent Defective)

nz A z B

( ) ( )

* arcsin * arcsin2 20 1

2

01

The acceptance number (c) (number of “defects” per sample permitted) can be determined by the following expression:

= Producer’s Risk = Consumer’s Risk = AQL (Average Quality Level) = LTPD (Lot Tolerance Percent Defective) n = Required Sample Size c = Acceptance Number (Number of Defects Permitted in Sample)

2

c =

01

]2/)(sin[arcsin* 0 nAnc