ANALYSIS OF PLASTIC FLOW INSIDE THE FAMILY MOULD

By

MOHD AMRAN ALI

Project Paper submitted to Department of Mechanical and Manufacturing, Faculty of

Engineering, Universiti Putra Malaysia, in Partial FulCillment of Requirements for the

Degree of Master of Manufacturing Systems Engineering

May2006

ACKNOWLEDGEMENTS

I would like to thank to my supervisor, En. Zulkiflle Bin Leman, lecturer in Department of

Mechanical and Manufacturing, Faculty of Engineering, Universiti Putra Malaysia for his

guidance, comments, sharing ideas, trustfully and supportive effort from starting until

completing this project.

I would also like to take this opportunity to thank my project examiner, Associate Professor Dr.

Shamsuddin Sulaiman, Deputy Dean (Academic), Faculty of Engineering, Universiti Putra

Malaysia for his effort and guidance in correcting this project.

This project is combination three software and using electronic cash register (ECR) product as a

model for analysis. For this I would like to thank the individuals stated below for their time to

share information and ideas.

Unigraphics software instructor

Mr. Hafiz.al Abu Bakar

Universiti Putra Malaysia

Rhinoceros and Moldex software instructor

Mr. Nar Hai Shih

Coretech System (M) Sdn. Bhd.

Provide hardcopy of ECR product drawing

Mr. Chong Poh Wai

AOBA Electronics Co., (M) Sdn. Bhd.

Finally, I would like to express my hearties sincere appreciation to KUTKM which has given

opportunity to me to further my study and given the sponsorship during my study at UPM.

11

DEDICATION

In the name of Allah the most gracious most merciful, for my lovely mother and late father by

hoping Allah will bless you and Allah will love you as you love me when I was a child. Thank

you for your support and for your efficacious prayer. For my wife Fatonah Binti Daud who

understands my commitment and all my children; Muhammad Fikri Arif, Muhammad Amsyar

Arif, Fatini Arfah and Muhammad Afnan Arif you are always on my heart. I hope all of us will

be given guidance and piety by Allah swt and success in the world and hereafter.

111

ABSTRACT

This project involved the flow analysis on an Electronic Cash Register (ECR) housing using

Moldex software. There were three parts in ECR housing which included top case, bottom case

and paper holder. Demand on this ECR product has tremendously increased, so these three

mould need to be changed from single cavity into family mould because the cost of fabrication

family mould and the cost of production using family mould is cheaper than single cavity. This

project started with design the parts in 30 modeling in the Unigraphics software and then using

Rhinoceros software as post processing and finally using Moldex software for flow analysis in

2-plate and 3-plate mould. In the Moldex software the filling melt front time, packing melt front

time, cooling and warpage analysis were done to determine and solve the part defects which

included short shot, unequal filling, over filling, welding l~e, cooling time and warpage

measurement. Calculations were done to determine the size of gate, runner and sprue to ensure

the smooth flow of plastic material into the cavities area. In addition , calculations were used

for the water holes design based on the distance of parts surface and the distance between

external diameters of water holes. The modifications were made in 2-plate mould on the gate

size of paper holder by increasing it to 25% due to the short shot problem and the gate size of

bottom case was reduced by 25% due to the over filling in the cavity area. Moreover, to

overcome the short shot problem the paper holder part was located near to the centre of mould.

Furthermore, modifications were made in 2-plate mould and 3-plate mould due to the welding

line problem on top case. Finally, water holes were redesigned again from straight to the

slanting position for better cooling time. It can be concluded that this project showed

encouraging results for all the three parts of ECR product. It solved various problems such as

short shot, unequal filling, overfilling, welding line, cooling time and warpage on the all three

parts.

iv

ABSTRAK

Projek ini terlibat dalam penganalisaan aliran suatu perumahan iaitu Pencatat Wang Tunai

Elektronik menggunakan perisian Moldex. Terdapat tigajenis produk iaitu selongsong atas,

selongsong bawah dan pemegang kertas. Permintaan keatas ECR produk ini semakin

bertambah maka ketiga-tiga acuan ini perlu ditukarkan kepada acuan keluarga disebabkan oleh

kos membuat acuan keluarga serta kos pengeluaran menggunakan acuan keluarga lebih murah

berbanding acuan satu rongga. Projek ini bermula dari merekabentuk model tiga dimensi

dalam perisian Unigraphics dan telah dipindahkan kedalam perisian Rhinoceros untuk pra

prosses dan akhimya ke perisian Moldex untuk penganalisaan peringkat akhir. Ianya dilakukan

keatas kedua acuan 2-plat dan 3-plat. Didalam perisian Moldex penganalisaan masa hadapan

cairan isian, penganalisaan masa hadapan cairan padatan, penganalisaan penyejukan dan

penganalisaan ledingan telah dijalankan untuk menyelesaikan dan meramalkan masalah pada

produk seperti pengisian tak cukup, pengisian tak seimbang, pengisian lebihan, garisan

kimpalan, masa penyejukan dan pengukuran ledingan. Pengiraan telah dilakukan keatas pintu

masuk, pelari, dan spru untuk memastikan pengaliran berkesan ke kawasan rongaan. Tambahan

lagi, pengiraan keatas lubang air juga telah dilakukan berdasarkanjarak permukaan produk ke

lubang air dan jarak diantara kawasan luar lubang air. Didalam acuan 2-plat, saiz untuk pintu

masuk untuk pemegang kertas telah ditambahkan ke 25% untuk menyelesaikan masalah

pengisian tak cukup manakala pintu masuk untuk selongsong bawah telah dikurangkan 25%

untuk menahan keadaan lebihan. Untuk meyelesaikan masalah pegisian tak cukup kedudukan

pemegang kertas telah dianjakan kearah pusat acuan. Malah, pengubahsuaian telah dilakukan

keatas acuan 2-plat dan acuan 3-plat kerana masalah garisan kimpalan pada selongsong atas.

Akhirnya, kedudukan lubang air telah direkabentuk semula dari lurus ke condong untuk

mengurangkan masa penyejukan. Ianya boleh disimpulkan bahawa projek ini menunjukkan

keputusan penganalisaan yang mengalakan keatas ketiga-tiga produk Pencatat Wang Tunai

Elektronik. Ianya telah menyelesaikan masalah pengisian tak cukup, mengisian tak seimbang,

pengisian lebihan, garisan kimpalan, masa penyejukan dan pengukuran ledingan keatas ke tiga­

tiga bahagian dalam acuan 2-plat dan 3-plat.

v

APPROVAL

This project submitted to the Department of Mechanical and Manufacturing, Faculty of

Engineering of Universiti Putra Malaysia has been accepted as a partial fulfillment of the

requirements for the Degree of Master of Manufacturing Systems Engineering. The members of

the examination Committee are as follows:

Supervisor

En. Zulkiflle Bin Leman

Department of Mechanical and Manufacturing

Faculty of Engineering

Universiti Putra Malaysia

~r c..

Examiner

Dr. Shamsuddin Sulaiman,

Associate Professor

Faculty of Engineering

Universiti Putra Malaysia

Vl

DECLARATION

I hereby declare that the project paper is based on my original work except for quotations and

citations, which have been duly acknowledged. I also declare that it has not been previously or

concurrently for any other degree at UPM or others institutions.

MO~~! DATE: \~ t;" J zcs6b

vu

TABLE OF CONTENTS

Page

ACKNOWLEDGEMENTS ............................................................................ ................ ....... ii

DEDICATION ........ ...... .............. .... .................. ..................... ...... ..................... .... ...... .......... iii

ABSTRACT ..................... ·································································································· IV

ABSTRAK ........................................................................................................................ v

APPROVAL .................................................. ........................................... ................ .......... Vl

DECLARATION ......................... ........................................................................................ vii

TABLE OF CONTENTS ..... ................................. .............................................................. viii

LIST OF TABLES ........................................ .... .. ..................... ..... ................................ ...... xiii

LIST OF FIGURES .............................................................. ........... ....... ............................ xiv

LIST OF ABBREVATIONS ............... .......... .......................... ..................... ...... .............. .. xix

CHAPTER I

1.0 INTRODUCTION ........................... ................................................ ............. I

I. I Background ......................................................... ................ ................................... I

I .2 Problem statement ...... ........... ...... ..... ..... ...... ..... ..... ...... .... ................. ........... ........... 2

I .3 Objective ..... .............................. ..... ..... ...... ..... ..... ........... ....................................... . 5

1.4 Scope ............. ........ ............. ..... .... ..... ..... .. ..................... ..... ................ ........... .......... 5

CHAPTER2

2.0 LITERATURE REVIEW .... ..... .......... ........... ............ .... ........... .......... ......... 6

2. I Plastic materials ..................................................................................................... 6

2.1. I Thermoplastics ........ ....................................................................................... 6

2.I.2 Types of Thermoplastics Materials ................................................................ 7

2.2 Characteristics of Acrylonitrile-Butadiene Styrene ..................................... ..... ..... 9

2.2. I Common name ............................................................................................... 9

2.2.2 Abbreviation .......... ..................... ..................... ...... ..... ................. ................... 9

2.2.3 Systematic chemical name: ............................ ............. ~ .................................. 9

2.2.4 Suppliers and trade names .............................................................................. 9

2.2.5 Material properties ..... ..................... ...... ...................... .... .. ........................... 1 O

Vlll

2.2.6

2.2.7

2.2.8

2.2.9

2.2.10

2.2.11

2.2.12

2.2.13

2.2.14

2.2.15

2.2.16

2.2.17

2.2.18

2.2.19

2.2.20

2.2.21

2.2.22

2.2.23

2.2.24

2.2.25

2.2.26

2.2.27

2.2.28

Ease or flow ....... ...... , .......................................................... ................ .......... 10

Shrinkage ....... ........................... ................................................................... 10

Resistant to the following ............. ............................... ................................ 10

Not resistant .............................. ................................................. .................. 10

Material detection or identification .............................................................. 11

Colouring .................. ................ ............ .... ............................................ ....... 11

Material and component handling ....................... ................ , ........................ 11

Mould and gate considerations .................................... .... .. ..... ...................... 12

Flow path ................................................... ........................................... ........ 12

Projected area .............................................. ................................................. 12

Cylinder equipment ............... .......................................... ..... ........................ 12

Screw cushion ... ...................... .......... ...................... ..................................... 12

Shot capacity .............................. ................................................................. . 12

Melt temperature - in the nozzle or an air- shot technique .......................... 13

Barrel residence time .................................................................................... 13

Temperature settings .................................................................................... 13

Injection speed - mould filling speed ........................................................... 13

Injection pressure .................. ..................... .... ............ ................ .................. 14

Screw rotational speed (rpm) ... ........... ................ ..................................... .... 14

Back pressure .. ...... ...... ........... ..... ..... .......... ..... ............ ..................... ............ 14

Shutting down ...... ........................... ............... .............................................. 14

Reprocessing ........................... .......... ...... ..... ..... ........... ........... ............... ..... . 14

Finishing ..................................... ................................................. ................. 14

2.2.29 Other comments .. ...... ..... ..... ........... ..... .......... ...... .......................... ...... ......... 15

2.2.30 Typical components ..... ................ ............... ................................ ................. 15

2.3 Mould .......................... .................................. .......... ..... ........... .......................... ... 16

2.3 .1 Basic terminology ................................... ................. ........... ...................... ... 16

2.3.2 Characteristics of plastic injection mould ........ ................. .............. ............. 16

2.3.3 Components of mould ............... ................ ........... ...................... .................. 22

2.3.4 2-Plate mould .... ..... ...................................................... .... ...... .......... ..... ...... 30

2.3.5 3-Plate mould . . . ..... .. ...... .. . .............. ... .. ... . . . . .......... . . ... . . ... .. . ... 32

IX

2.3.6 Visible defects on plastic part ....... ....................................................... ........ 34

CHAPTER3

3.0 METHODOLOGY .............................................................................. .... ... 36

3.1 Introduction ...... ............................... ..... ..... .......... ...... .......... ................ ................. 36

3.2 Flowchart of product development ............................... ................ ................ ....... 38

3.2.1 Design part in 3D using Unigraphic .. ..................................................... ..... 39

3.2.2

3.2.3

3.2.4

3.2.5

3.2.6

3.2.7

3.2.8

3.2.9

3.2.10

3.2.11

CHAPTER4

Transferring file from Unigraphic to Moldex software ............................... 43

Meshing part surface ............................................................... ..................... 43

Circular layout design .................................................................................. 44

Design gate system .............. ..... ........... ..................................... .................... 45

Design of sprue system ..................................... ...... ...... ...... .... ..................... 50

Design of runners .................................. ..... ........... ........... ..... ....................... 53

Design of straight type water hole ...... ..................................... ...... ...... ........ 57

Set processing condition .............................................................................. 58

Select material ........... ..... ................................................ .............................. 58

Run analysis .......... .. .... ................ .................................. .... ...... .... ................. 58

4.0 ANALYSIS OF 2-PLATE MOULD ...... ........... ..... ........... ..... ...... ..... ..... ... 60

4.1 Export/import file ................................................................................................. 60

4.1.1 Imported file of top case .. .... ..... ........... ..... ................ ...... ................ .......... ... 60

4.1.2 Imported file of bottom case ............... ...... ................ ................ ........... ........ 64

4.1.3 Imported file of paper holder ............ .... ...... .......... .................. ..... ......... ....... 65

4.2 Layout of electronic cash register ...................... ..... ........... ................ .................. 66

4.3 Size of rectangulf1I edge gate ...... .... ................. ........... ..... ..... .......... ...... ..... ..... ..... 67

4.3.1 Depth of edge gate ............. ..... ..... ................................ ................................ 67

4.3.2 Width of edge gate ..... ..... ...... ..................... ..... ..................... ..... ...... ............. 68

4.4 Full dimension of gate ............... : ................ ......................................................... 69

4.4.1 Gate of top case ..................................... ................. ...... ..................... ........... 69

4.4.2 Gate of bottom Case ............................. ........................................................ 69

x

4.4.3 Gate of paper holder .......................... .................................................... ....... 69

4.5 Circular runner ........................ ...... ....................................................................... 70

4.5.1 Runner of top case ................................... ................ ...... .......... ......•... ........... 70

4.5.2 Runner of bottom case ............................................................................ ..... 71

4.5.3 Runner of paper holder ................................................................................. 71

4.6 Sprue .................................................................................................................... 72

4. 7 Cold slug well size ....................................... ........................................................ 73

4.8 Mould base and water hole size ...................... ......... ................. ..... ...................... 74

4.9 First filling analysis of2-plate mould .................................................................. 75

4.9.1 Plastic material .................... .............................. ...... ........... .......................... 76

4.9.2 Feed system and part thickness .................................................................... 77

4.9.3 First filling analysis ... .......................... ...... .............................................. ..... 79

4.10 First modification of2-plate mould .................................................................... . 81

4.10.1 Modified gate and runner of bottom case .................................................... 81

4.10.2 Modified gate and runner of paper holder ........................... ............... .......... 81

4.10.3 Modified thickness of top case .............................................. ....................... 83

4.10.4 Second filling analysis of 2-plate mould ............................. ......................... 84

4.11 Second modification of2-plate mould ................................................................. 86

4.11.1 Third filling analysis .................................................................................... 87

4.11.2 Packing analysis .............. ................ ............... ..... .............................. ..... ...... 90

4.11.3 Straight water holes ................. ..................................................................... 91

4.12 Slanting water holes ....... ..................... .......... .......... .................... ......................... 93

4.12.1 Cooling analysis .................... .......... .......... ..... .............................................. 93

4.12.2 Warpage analysis ...................................... ..... .............................................. 94

4.13 Discussion on 2-plate mould .. ... . ........... . .............. . ........................... 94

CHAPTERS

5.0 ANALYSIS OF 3-PLATE MOULD ....... ........... ....................................... 97

5.1 Size of pin point gate .................................................. ........................................ . 97

5.1.1 Diameter pin point gate for top case ....... ..... .......... ...................................... 97

5 .1.2 Diameter pin point gate for bottom case ................... ................................... 98

xi

5 .1.3 Diameter pin point gate for paper holder ..................................................... 99

5.1 .4 Secondary sprue ....................... ...... ..................... ....................................... 101

5.2 First filling analysis of 3-plate mould ................................................................ 102

5 .2.1 Filling analysis ................................ .......... ...................... .......... ................. 102

5.3 First modification of3-plate mould ................................................................... 104

5.3.1 Second filling analysis ..... ..... ..................................................... ............... . 104

5 .3 .2 Packing analysis ............................................................................. ............ 107

5.3.3 Cooling analysis of 3-plate mould .................................................. ........... 108

5.3.4 Warpage analysis of3-plate mould ........................... ...... ..... ................ ...... 109

5.4 Discussion on 3-plate mould ...... ........................................................................ 110

5.5 Summary comparison results ........ . . .......... ...... . .... ................... ........ 111

CHAPTER6

6.0 CONCLUSION ........................................................................... .............. 112

6.1 Recommendation for future research .............................................................. ... 113

REFERENCES

BIODATA OF THE AUTHOR

APPENDICES

XU

LIST OF TABLES

Page

Table 2-1: Supplier and trade names ............................ ............................... ....................... 9

Table 2-2: Different zone temperature at barrel.. ............................................................. 13

Table 3-1: CAD model conversion format ...................................................................... .43

Table 3-2: Plastics material constant. .......................... .... ................................................. 48

Table 3-3: C value of the wall thickness (t) .............................................................. ....... 50

Table 5-1 : Constant C .................................................................................................... 100

Table 5-2: Comparison result . ..... .. .. . .......... .. . .... .. .... . . ......... .. . ... ... .... .. .... . .. 111

X111

LIST OF FIGURES

Page

Figure 1-1: Electronic Cash Register ................................................................................. 3

Figure 1-2: Part of top case ......................................... ................ .... ............ ....................... 4

Figure 1-3: Part of bottom case .......................................................................................... 4

Figure 1-4: Part of paper holder ........................................................................................ 4

Figure 2-1: Basic mould consisting of cavity and core plate ........................................... 16

Figure 2-2: Impression in plastics injection mould ....... .......................................... ......... 17

Figure 2-3: Feeding system including sprue, runner, and gate ........................................ 18

Figure 2-4: Sprue, runner, gate, moulding and cold slug well ......................................... 19

Figure 2-5: Location of gate ............................................................................................. 20

Figure 2-6: Air vent through mould parting line ....................................................... ....... 21

Figure 2-7: Water cooling located inside the mould ........................................................ 22

Figure 2-8: Locating ring mounted at top clamping plate ..... .................................... ....... 23

Figure 2-9: Sprue bushes (a) Spherical seating and (b) Flat seating ................................ 24

Figure 2-10: Guide pillar and guide bush ......................... .......... ..... ............... ....... ..... ..... 24

Figure 2-11: Various types of ejector elements ............................................................... 25

Figure 2-12: Location of ejector pin ................................................................................ 26

Figure 2-13: Step ejector pin ............................................................................................ 27

Figure 2-14: Ejecting a moulding for a box lid by means ofD-shape ejector pin ........... 27

Figure 2-15: Sleeve ejector pin ........................................................................................ 28

Figure 2-16: Ejector blade using in slender moulding .... ................................................. 29

Figure 2-17: 2-plate mould .. .... ................. ..... ..... ..... ................................. ...... ................. 30

Figure 2-18: 3-plate mould .............................................................................................. 32

Figure 2-19: Point system of visible defects on plastic part ............ ................................ 34

Fi 2 20· E 1 . tur . d .c. • 1 . . . . uld. 35 gure - . xamp e pie es vanous eiect m p ast1c mJectlon mo mg .................. .

Figure 3-1: Conventional approach product development ...... ..................... ..... ...... ......... 36

Figure 3-2: Interaction of mould design, product design and part performance ....... ....... 37

Figure 3-3: flowchart of product development ................... ............................ ..... ........... .38

Figure 3-4: Model of 3D top case in Unigraphic ... ...... .................................................... 39

XlV

Figure 3-5: Radius profile at 3D top case ... ............................................ ................ ........ .40

Figure 3-6: Completed shape of the 3D top case ................ ...................................... ...... .40

Figure 3-7: Drafting 2D of top case ................. ................................................. ...... ......... 40

Figure 3-8: Drafting 3D of bottom case .......................................................... .............. .. .41

Figure 3-9: Drafting 2D of bottom case ............................................. .............................. 41

Figure 3-10: Drafting 3D of paper holder .. ........................................... .......................... .42

Figure 3-11: Drafting 2D of paper holder ....................................................................... .42

Figure 3-12: Element having three nodes ................... ............... ...................................... 44

Figure 3-13: circular layout with 4 cavities ..................................................................... 44

Figure 3-14: Electronic cash register use circular layout.. ................ .......... .................... .4 5

Figure 3-15: Rectangular edge gate ...................................................................... ........... 46

Figure 3-16: Depth (h) for rectangular edge gate ............... ......... ....... ......................... .... .47

Figure 3-17: Width (w) for rectangular edge gate ........................................... ............... .48

Figure 3-18: Methods to locate the rectangular edge gate ............................................... 48

Figure 3-19: Shape of pin point gate ................................................. ...................... ......... 49

Figure 3-20: Suggested dimension for pin point gate ................................................... ... 50

Figure 3-21: Sprue location at 2-plate mould .................... ...................... ..... ........... ..... ... 51

Figure 3-22: Sprue location at 3 plate mould ........ ................ .......... ...... .......... ................. 51

Figure 3-23: Guide lines for dimensioning sprue ............................................................ 52

Figure 3-24: Reverse taper cold slug well sprue puller .......... ..... ...... .......... ...... ............... 53

Figure 3-25: Circular cross section runner ....................................................... ........... ..... 54

Figure 3-26: Parabolic cross section runner ...................... ............ ........... ......... ........... .... 54

Figure 3-27: Diagram 1 applicable for PS, ABS, SAN and CAB ..... ............................... 55

Figure 3-28: Diagram 2 Correction diameter of runner .. .... ................ ...... ...... ................. 55

Figure 3-29: Diameter of runner ......................... .......................................................... ... 56 . Figure 3-30: Guideline of water hole .......................................... ................ ........... ..... ..... 57

Figure 4-1: Solid modeling of top case ................ ............................................................ 60

Figure 4-2: Mesh modeling of top case ......................... ..... ..... ................. ..... ..... .............. 61

Figure 4-3: Early aspect ratio .................. ............... ..................................... ..................... 61

Figure 4-4: Refine meshing of top case .......... ..... ................ ..... ................ .... .. .... ..... ........ 62

Fi 4 5· Final . gure - . aspect ratio ............. ...... ........... .................... ......................................... 62

xv

Figure 4-6: Separation process between cavity and core side ......................................... 63

Figure 4-7: Cavity side of top case .............. ......... ........................................................... 63

Figure 4-8: Mesh modeling of bottom case ..................................................................... 64

Figure 4-9: Refine meshing of bottom case ............................................ ......................... 64

Figure 4-10: Cavity layer of bottom case .............................. ........................................... 64

Figure 4-11 : Mesh modeling of paper holder .............. ................................. ................... 65

Figure 4-12: Refine meshing of paper holder ............................................................. ..... 65

Figure 4-13: Cavity of paper holder .................... ..... ........................................... .......... ... 65

Figure 4-14: 2-plate mould I.,ayout .............................................................. .................... 66

Figure 4-15: Gate of top case .. ............ ..................... ................................................ ........ 69

Figure 4-16: Gate of bottom case ..................................................................................... 69

Figure 4-1 7: Gate of paper holder ........................................................................ ............ 69

Figure 4-18: Runner of top case .............. ..... .................................................................... 70

Figure 4-19: Runner of bottom case .... ................................ ............ ..... .......... .................. 71

Figure 4-20: Runner of paper holder ................................................................................ 72

Figure 4-21: Size of sprue ................................................................................................ 72

Figure 4-22: Size of cold slug well .................................................................................. 73

Figure 4-23: Completed feeding system and parts ...... ................ ........... ..... .... ....... .......... 73

Figure 4-24: 2D drawing ofwaterhole ............................................................................ 74

Figure 4-25: Location of water hole ............................ .......... ........................................... 74

Figure 4-26: Initial process condition .............................................................................. 75

Figure 4-27: Final process condition ................................. ........... ........... ..... ................... 76

Figure 4-28: Graph viscosity versus shear rate ........... ................ ........... .......................... 76

Figure 4-29: General information of ABS material ......................................................... 77

Figure 4-30: Feeding system and parts thickness ......... ...................... ............................. 77

Figure 4-31: Completed design of 2-plate mould ..................... ...... ................ ................. 78

Figure 4-32: Stages of first filling analysis ..................................................... ........... ...... 79

Figure 4-33: Welding line on side body of top case .................... ........... ......................... 80

Figure 4-34: New diameter of bottom case gate .............................................................. 81

Figure 4-35: New diameter of bottom case runner .......................................................... 81

Figure 4-36: New diameter of bottom case runner ...... ........... ......................................... 81

XVI

Figure 4-37: First modified of feed system ........................................... ........................... 82

Figure 4-38: Flow front area ......................................................................... ................... 82

Figure 4-39: First modification of2-plate mould ............................................................ 83

Figure 4-40: Stages of second filling analysis .................... .... ...... ........................... ........ 84

Figure 4-41 : Welding line after first modification ....................................................... .... 85

Figure 4-42: Second modification of2-plate mould ....... .......... ................ .................... ... 86

Figure 4-43: Stages of third filling analysis ...................................... ............................... 88

Figure 4-44: Welding line after second modification .......................... .......... .................. 89

Figure 4-45: Stages of packing analysis ........................................................................... 90

Figure 4-46: Cooling analysis - straight water holes ............................ .... ....................... 91

Figure 4-47: Warpage analysis - straight water holes ......... ............................................. 92

Figure 4-48: Cooling analysis - slanting water holes ....................... ......................... ...... . 93

Figure 4-49: Warpage analysis - slanting water holes ... .................................................. 94

Figure 4-50: Result of welding line after first modification .. ..................... .... ................. 95

Figure 4-51: Result of welding line after second modification . .... .... . ..................... 96

Figure 4-52: Result of paper holder shifted from 50mm to 25mm ... ............................... 96

Figure 5-1 : Pin point gate of top case ............. ..... ................................................ ........... 98

Figure 5-2: Pin point gate of bottom case .... ..... ......................... ...... ...... ................ .... ..... 99

Figure 5-3: Value constant C ........................................................................................... 99

Figure 5-4: Pin point gate of paper holder .......... ................ ........................................... 100

Figure 5-5: Secondary sprue of 3-plate mould ............................................................... I 01

Figure 5-6: Completed design of 3-plate mould ... .... .......... ...... ..... ...... ..... ..... ..... ........... 101

Figure 5-7: Filling stages of 3-plate mould .................................................................... 103

Figure 5-8: Welding line after first filling ..................................................................... 103

Figure 5-9: Modifications of top case ....................... .......................................... ........... 104

Figure 5-10: Stages of second filing analysis ... .... .......... ........... ...... ..................... ......... 106

Figure 5-11: Welding line after first modification ......... ................................................ 106

Figure 5-12: Stages of packing analysis ......................................................................... 107

Figure 5-13: Cooling analysis of 3-plate mould ............................................................ 108

Figure 5-14: Warpage analysis of 3-plate mould .......... ............................... .................. 109

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Figure 5-15: Additional material .................................................................................... 110

Figure 5-16: Result of welding lines after modification ................................................ 110

Figure 6-1: Air vents location for 2-plate mould ........................................................... 113

Figure 6-2: Air vents location on 3-plate mould ............................................................ 114

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LIST OF ABBREV ATIONS

ECR - Electronic Cash Register

ABS - Acrylonitrile Butadiene Styrene.

PMMA - Polymethyl Methacrylate (Acrylic)

PP - Polypropylene

PE - Polyethylene

PE - Polyethylene

LDPE - Low Density Polyethylene

HDPE - High Density Polyethylene

PS - Polystyrene

HIPS - High Impacts Polystyrene

XIX

CHAPTER I

1.0 INTRODUCTION

1.1 Background

Plastic materials are the most important material in the world which are usually used in

agriculture, appliances, clothing, construction, electronics, furniture, packaging, transportation,

and numerous other areas. It can be said that almost in every human life activity, directly or

indirectly involves the products made from plastic materials.

There are many processes can be used to produce the plastic product such as injection process,

extrusion process, blow process, compression process, transfer process and rotating process.

The most popular process which can produce high mass production and complicated shape is

injection process. In injection process, mould is needed which it can be attached to the injection

machine to produce plastic part.

Mould is a tool to produce plastic parts. To get one mould involves various stages, from design

stage where the mould need to be designed using Computer Aided Design software and then

machine the raw materials to become mould parts and finally, assembly the mould parts to

become one complete set of mould.

It is very important to get good appearance such as no welding line, sink mark, accurate

dimension, flatness, and the most important capable to assemble to other parts. Some plastic

parts are produced using injection machine have various problems such as welding line, sink

mark and etc., due to various factors such as wrong gate location, wrong size of gate, wrong

size of runner, wrong length of runner, wrong location of water hole and other factors that

affect the quality of plastic part.

In the past few years, many mould makers have used trial and error method to produce mould

where they were usually very high skill people to assist on design stages. Sometime to produce

I

one set of mould had taken long time due to the many modifications and repairing at mould to

get good plastic part.

The defects of plastic part can be reduced by flow analysis on the plastic part at the design stage

which plastics part will be analyzed using flow analysis software. This analysis usually looks at

the various parameter such as flow front, flow rate, temperature different, shrinkage

distribution, air trap, optimum window condition and etc.

Design the mould in one cavity in one mould is easier than design many cavities in one mould

in term of gate location, size of gate, gate length and water hole location. The most difficult is

to design the family mould. This is because of every single part is different in terms of weight,

layout, shape, size that are more difficult to take decision on gate location, gate size and length

of gate and water hole.

1.2 Problem statement

The demand of Electronic Cash Register (ECR) product has tremendously increased, therefore

AOBA Electronics Sdn. Bhd. who the owner ofECR product has intention to invest by

fabricating a family mould because of two reasons. Firstly, the standard part cost of family

mould is more cheaper RM 1490.00 or approximately 17% than the standard part cost of single

cavity on each mould. Secondly, the cost of production using injection machine on each mould

reduced by using family mould which cheaper RM 70.00 per hour or approximately 39 %

when using only one injection machine. The detail of comparison cost between single cavity

mould and family mould as shown in Appendix 1.

These problems can be solved by designing one tooling including the top case, bottom case and

paper holder. The main challenge to design one tooling which including three parts are to

decide the injection location, the size of gates, runners, sprue, location of water hole and the

most important is the mould layout.

2

In this study, family plastic parts were analyzed using Moldex software. The family plastic

parts are consist of top case, bottom case and paper holder as shown from Figure 1-1 - 1-4.

Moldex software is used to analyse the optimum design of mould cavities layout, gates, runners

and sprue. The three dimensional shape will be drawn using Unigraphics software and then will

be exported to the Moldex software. Some tedious work need to do for repairing mesh surface

for three dimensional shape in Moldex software which many open area will be occurred at

surface. Repairing mesh surface need to do carefully because it will be affected the result of the

analysis. The capabilities of Moldex software are to optimize the injection location, design of

feed system including sprue, runner and gate, optimize the balance of feeds system, and predict

cycle time, shot size, clamp tonnage, shrinkage and cooling circuit.

Result from the Moldex software will be analyzed by taking consideration the parameters

involved such as optimum window parameters, shrinkage distribution, and balance of part

thickness, air trap, flow front temperature, warpage and various parameters. These parameters

will be collected and the optimum parameter will recommend for this family mould.

Figure 1 -1 : Electronic Cash Register

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Figure 1-2: Part of top case

Figure 1-3: Part of bottom case

Figure 1-4: Part of paper holder

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1.3 Objective

The aim of this project is to determine the optimum design of mould cavity layout, gate, runner,

sprue and water hole inside the family mould using plastics flow analysis.

The main objectives are:

• To determine the best location of top case, bottom case and paper holder at the

mould cavity layout.

• To find out the best location and size of gate, runner, sprue and water hole for this

mould.

• To analyse the different of filling, packing, cooling and warpage parameters

between 2-plate mould and 3-plate mould.

1.4 Scope

In this study four plastic parts which includes top case, bottom case and two parts from paper

holder are analyzed using flow analysis software. The simulation analyses are done on both 2-

plate mould and 3-plate mould. The analyses are done without carried out the mould

fabrication and experimental process. There are three software is used in this simulation

analysis. Unigraphics software is used to design the part in 3D solid modeling and Rhinoceros

software is used as post processing for meshing process, decision of mould layout, design of

gate, runner, sprue and water hole. In Moldex software the filling, packing, cooling and

warpage analysis is done to determine any defects on top case, bottom case and paper holder.

Results from simulation are analysed and modification will be done if any defects were found.

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