INVESTIGATION OF MOULD DESIGN AND PROCESS PARAMETER OPTIMISATION OF PLASTIC INJECTION MOULDING FOR THIN WALL PART AZNIZAM BIN AHMAD A thesis submitted in fulfillment of the requirement for the award of the Degree of Master of Mechanical Engineering TITLE Faculty of Mechanical and Manufacturing Engineering Universiti Tun Hussein Onn Malaysia MAY 2019
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PTTAPERP
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UN AMINAH
INVESTIGATION OF MOULD DESIGN AND PROCESS PARAMETER
OPTIMISATION OF PLASTIC INJECTION MOULDING FOR THIN WALL
PART
AZNIZAM BIN AHMAD
A thesis submitted in
fulfillment of the requirement for the award of the
Degree of Master of Mechanical Engineering
TITLE
Faculty of Mechanical and Manufacturing Engineering
Universiti Tun Hussein Onn Malaysia
MAY 2019
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DEDICATION
Special thanks to my strength on their support and cares, father, mother, wife and
kids.
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ACKNOWLEDGEMENT
First of all, thanks to Allah S.W.T for giving me the strength and chances in completing
this master thesis. In preparing this research report, I would like to express my sincere
appreciation and gratitude to my supervisor, Prof. Ir. Dr. Md. Saidin bin Wahab for his
guidance, critics and friendship along the journey to complete my study.
I would also like to thank to staff and lecturers in Universiti Tun Hussein Onn
Malaysia (UTHM) that have assisted me, their support and encouragement. May all
the good deeds that were done will be blessed by Allah S.W.T.
Last but not least, my greatest thanks from my deepest heart to my father,
Ahmad bin Ihsan, my mother Junaidah binti Sahib, my beloved wife Norasliza binti
Mohd Bisri, my kids Muhammad Faris, Muhammad Faiz and the rest of my family
member for their support. I just want them to know that I am very grateful to have
them whom always assisting me despite of many challenges that I had faced in
completing this research.
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ABSTRACT
In plastic injection moulding industries such as automotive, packaging and medical,
demands for thin wall parts increases for the reason of light weight, lower cycle time,
lower part cost and higher productivity. However, a lot of challenges faced by the
moulders since the mould and processing parameters are critical to produce good
quality of thin wall parts. This research describes the mould design and process
parameter aspects of thin wall part focusing on tubular shape The aim of the research
is to investigate the factors that influence the moulded part quality in terms of part
shrinkage and weight. The research begin with development of mould for a
polypropylene thin wall tubular part and followed by study on the effect of injection
moulding process parameter towards moulded part quality. In order to identify the
moulding parameters that influences the moulded part quality, Taguchi optimisation
method was employed in the research. Based on the obtained simulation result, the
preferred size of runner was diameter of 4 mm, gate size was 1 mm and the gate
number was 4 number for actual mould fabrication. On the effect of injection pressure,
the result shows that with increasing in injection pressure the part shrinkage reduced
and part weight increased. As for the effect of melt temperature, the result shows that
with increasing in melt temperature the part shrinkage increased and part weight
reduced. As for the optimisation, the result shows that temperature contributed
significantly to shrinkage and weight of moulded part. Mould temperature have
significant effect to outer diameter shrinkage while melt temperature have significant
effect to inner diameter shrinkage.
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ABSTRAK
Dalam industri pengacuanan suntikan plastik seperti automotif, pembungkusan dan
perubatan, permintaan untuk komponen dinding nipis semakin meningkat disebabkan
oleh ringan, masa kitaran yang lebih rendah, kos yang lebih rendah dan produktiviti
yang lebih tinggi. Walau bagaimanapun, banyak cabaran yang harus dihadapi oleh
pihak industri kerana acuan dan parameter pemprosesan adalah rumit bagi
menghasilkan komponen dinding nipis yang berkualiti. Kajian ini menerangkan aspek
reka bentuk acuan dan parameter proses dalam proses pengacuan suntikan plastik
(PIM) untuk menghasilkan komponen tiub dinding yang nipis. Tujuan penyelidikan
dijalankan adalah untuk mengkaji faktor-faktor yang mempengaruhi kualiti komponen
yang terhasil dari segi pengecutan dan berat komponen. Penyelidikan bermula dengan
pembangunan acuan untuk komponen tiub dinding polipropilena nipis dan diikuti
dengan kajian mengenai kesan parameter proses pengacuanan suntikan terhadap
kualiti komponen yang dihasilkan. Untuk mengenalpasti parameter pengacuanan yang
mempengaruhi kualiti komponen yang dihasilkan, kaedah pengoptimuman Taguchi
telah digunakan dalam penyelidikan. Berdasarkan hasil yang diperoleh, saiz pelayar
yang dipilih adalah 4 mm, saiz pintu adalah 1 mm dan bilangan pintu adalah 4 untuk
pembuatan acuan sebenar. Bagi kesan tekanan suntikan, hasilnya menunjukkan
bahawa dengan peningkatan tekanan suntikan, pengecutan komponen berkurangan
manakala berat komponen meningkat. Untuk kesan suhu leburan pula, hasilnya
menunjukkan bahawa dengan peningkatan suhu pencairan, pengecutan komponen
meningkat dan berat komponen berkurangan. Bagi pengoptimuman, dapatan
menunjukkan bahawa suhu menyumbang dengan ketara kepada pengecutan dan berat
komponen acuan. Suhu acuan mempunyai kesan ketara kepada pengecutan diameter
luar manakala suhu pencairan mempunyai kesan ketara kepada pengecutan diameter
dalaman.
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CONTENTS
TITLE i
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vi
CONTENTS vii
LIST OF TABLES x
LIST OF FIGURES xiii
LIST OF SYMBOLS AND ABBREVIATIONS xvi
LIST OF APPENDICES xix
CHAPTER 1 INTRODUCTION 1
1.1 Background of study 1
1.2 Problem statement 2
1.3 Objectives 4
1.4 Scope of study 4
1.5 Thesis outline 5
CHAPTER 2 LITERATURE REVIEW 6
2.1 Introduction 6
2.1.1 Mould for injection moulding 6
2.1.2 Simulation for injection moulding 11
2.1.3 Injection moulding process parameter 12
2.1.4 The effect of injection moulding process
parameter
13
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2.1.5 Optimisation in injection moulding 16
2.2 Polymer material for injection moulding 19
2.3 Thin wall part in injection moulding 22
2.4 Summary 25
CHAPTER 3 METHODOLOGY 26
3.1 Introduction 26
3.2 Development of mould 27
3.2.1 Runner size 33
3.2.2 Gate size 34
3.2.3 Gate number 35
3.2.4 Assembly and evaluation of mould design 36
3.3 Injection moulding process parameter 39
3.3.1 Short shot and injection pressure
comparison
41
3.3.2 The effect of process parameter on part
shrinkage
47
3.3.3 The effect of process parameter on part
weight
49
3.4 Optimisation of injection moulding process
parameter
51
3.4.1 Quality factor evaluation on part
shrinkage and part weight
55
3.4.2 Signal to noise ratio 56
3.4.3 Optimised injection moulding process
parameter
57
3.5 Summary 58
CHAPTER 4 RESULTS AND DISCUSSION 59
4.1 Introduction 59
4.2 Development of mould outcomes 59
4.2.1 Runner size result (simulation) 61
4.2.2 Gate size result (simulation) 63
4.2.3 Gate number result (simulation) 65
4.2.4 Assembly and evaluation of actual mould 67
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design result
4.3 Injection moulding process parameter outcomes 69
4.4.1 Short shot and injection pressure
comparison result
69
4.3.2 The effect of process parameter on part
shrinkage result
72
4.3.3 The effect of process parameter on part
weight result
74
4.4 Optimisation of injection moulding process
parameter outcomes
76
4.4.1 Part shrinkage result 76
4.4.2 Part weight result 78
4.4.3 Signal to noise ratio result 79
4.4.4 Optimised injection moulding process
parameter result
86
4.5 Summary 87
CHAPTER 5 CONCLUSION AND RECOMMENDATIONS 88
5.1 Conclusion 88
5.2 Recommendations 89
5.2.1 Mould design and development 89
5.2.2 Injection moulding process parameter 90
5.2.3 Optimisation of process parameter 90
5.2.4 Polymer material 90
REFERENCES 91
APPENDIX 99
VITA 121
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LIST OF TABLES
2.1 Simulation software used by previous researches 11
2.2 Process parameter in injection moulding used by previous
researches
13
2.3 Previous researches study involved on mould temperature 14
2.4 Previous researches study involved on melt temperature 15
2.5 Previous researches study involved on injection time 15
2.6 Previous researches study involved on injection pressure 16
2.7 Design of experiment (DOE) method used by the previous
researches
17
2.8 ANOVA method used by previous researches 18
2.9 Hypothesis of process parameter for shrinkage response
(Hindle, 2018)
19
2.10 Differences in homopolymer and copolymer (Charles &
Carraher, 2012)
21
2.11 Advantages and disadvantages of polypropylene (Maddah,
2016)
21
2.12 Specification of Titanpro® PM803 (M-Base Engineering,
2015)
21
2.13 Thermoplastic material in injection moulding used by
previous researches
22
2.14 Maximum (L/t) ratio for few common polymer materials
(Mastip, 2015)
23
2.15 Definition of the thin wall by previous researches 24
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2.16 Recommended wall thickness for the polymer material
(Berlin, 2017)
25
3.1 List of considered polymer materials 31
3.2 Typical properties of polypropylene polymer material used
in the experiment (M-Base Engineering, 2015)
32
3.3 Key characteristics of typical mould material (Beaumont et
al., 2002)
33
3.4 Specification for plastic injection mould 33
3.5 Factors related to runner size 34
3.6 Factors related to gate size 35
3.7 Factors related to gate number 35
3.8 Initial Processing Parameter for the simulation of moulding 40
3.9 Typical polymer material properties polypropylene
Titanpro® PM803 (Titan, 2017)
40
3.10 Short shot comparison process parameter 42
3.11 Injection pressure comparison process parameter 43
3.12 Comparison of various pressure transducers (Rauwendaal,
2000)
44
3.13
Effect of injection pressure towards part shrinkage process
parameter
47
3.14 Effect of melt temperature towards part shrinkage process
parameter
47
3.15 Effect of injection pressure towards part weight process
parameter
50
3.16 Effect of melt temperature towards part weight process
parameter
50
3.17 Factor and level selection for part shrinkage and part
weight
52
3.18 Orthogonal array for part shrinkage and part weight 52
3.19 Standard specifications of Matsui mould temperature
controller
53
3.20 List of polymer material for mould temperature controller
setting
54
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3.21 Quality characteristics and the formula (Michaeli &
Wolters, 2000)
56
4.1 Result of melt flow rate for considered polymer materials 60
4.2 Result of factors related to runner size 61
4.3 Result of factors related to gate size 63
4.4 Result of factors related to gate number 65
4.5 Comparison of the flow length between simulation and
experiment at different injection time
70
4.6 Simulation and experiment shrinkage result 77
4.7 Comparison of shrinkage result between experimental and
simulation
78
4.8 Difference percentage between simulation and
experimental of part weight
79
4.9 The S/N ratio value for inner diameter shrinkage at 37.50
mm
80
4.10 The S/N ratio value for outer diameter shrinkage at 37.50
mm
80
4.11 The optimum parameter to control inner diameter
shrinkage at 37.50 mm
81
4.12 The optimum parameter to control outer diameter
shrinkage at 37.50 mm
82
4.13 ANOVA result for inner diameter shrinkage at 37.50 mm 83
4.14 ANOVA result for outer diameter shrinkage at 37.50 mm 83
4.15 The S/N ratio value for part weight 84
4.16 The optimum parameter to control part weight 85
4.17 ANOVA result for part weight 85
4.18 Confirmation test result for inner diameter shrinkage at
37.50 mm
86
4.19 The confirmation test result for outer diameter shrinkage at
37.50 mm
86
4.20 Margin error in experimental of ID and OD shrinkage 86
4.21 Confirmation test result for part weight 87
4.22 Margin error in experimental of part weight 87
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LIST OF FIGURES
2.1 A plastic injection moulding system (Rosato & Rosato,
2000)
7
2.2 Two plate cold runner mould system (Clara, 2006) 10
2.3 The position of stripper in a mould (Misumi, 2018) 10
2.4 The processing effects on thermoplastic polymer (IMould,
2009)
20
2.5 Thin wall injection flow (Mastip, 2015) 24
3.1 Overview of the work flow process for the research 27
3.2 Cross section drawing of cup in AutoCAD 29
3.3 A cup part modeling in SolidWorks 29
3.4 Part in 3D printing process using UP Mini 3D Printer 30