AN OPTIMIZATION OF THE PLASTIC INJECTION MOLDING...

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AN OPTIMIZATION OF THE PLASTIC INJECTION MOLDING

PARAMETERS FOR SPORT EQUIPMENT BY USING DOE METHODS

RADHWAN BIN HUSSIN

A project submitted in partially fulfillment of

the requirements for the award of the Master Degree in

Mechanical Engineering (Advanced Manufacturing Technology)

Faculty of Mechanical Engineering

Universiti Teknologi Malaysia

JANUARY, 2013

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ABSTRACT

This thesis, research about the defect on plastic product in injection molding

process. During producing a product using injection molding process, various of

defects such as warpage, weld lines, shrinkage and sink mark can be occurred. A set

of Optimal setting of injection molding parameters is very important to be

determined after various trials has been made, because to reduce and controlling the

quality on defect of the injection molded product. The purpose of this research is to

minimizing warpage and shrinkage defect on material Polycarbonate(PC)

thermoplastic and simulate the injection molding process using Moldflow Plastic

Insight software (MPI).Optical glasses has been selected as a product to be

studied and design the model by using Unigraphic NX 7.5. The approach based on

Design of Experiment (Taguchi Method) has been implemented to analyze and

optimize the processing parameters such as mold temperature, melt temperature,

packing time, packing pressure, cooling time, cooling temperature, and runner size.

Experimental plans available in the form of Orthogonal Arrays. Minitab Software

using for automatic experiments design and analysis of results based on Design of

Experiments (Taguchi Method) to find the best setting of injection molding plastic

part.

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ESPECIALLY DEDICATED TO

My beloved wife

Noorzalifah Bt Mohamed

My supportive parents

Hussin Bin Talib

Rosnah Bt Saad

My wonderful brothers and sisters

Noraini Binti Hussin

Rushidan Bin Hussin

Razaidi Bin Hussin

Razi Bin Hussin

Mohd Khairi Bin Hussin

Munirah Binti Hussin

And last but not least to all my relatives and my close friends

Thank you for all the prayers, courage, confident and trust that you all gave to me.

May Allah bless all people that I love and it’s my honor to share this happiness with

my love ones.

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ACKNOWLEDGEMENTS

First of all, I would like to express appreciation to thank my supervisor Mr.

Rozaimi Bin Mohd Saad for his guidance and advice, without it I would not be able

to achieve the objective of my project. His Wisdom and determination have become

a source of inspiration, demand to meet the level of quality and perfection be a

challenge for me. It taught me to learn beyond the reach of what has been learned in

class.

Secondly, I would like to express special thanks to all lecturers for Advanced

Manufacturing Technology course especially to Mr Jafri Bin Mohd Rohani give a

good knowledge of Design of Experiments (DOE), Dr Ariffin Bin Haji Abdul Razak

taught me in the manufacturing process and Dr Khidzir Bin Zakaria with Mr

Roslan@Iskandar Bin Ismail technical staff CADCAM laboratory the help and

support in completing this project.

Finally, I would also like to express my special thanks to my wife and my

family for believing in me and always supported me throughout this project. I would

like to thank those who have contributed directly or indirectly to the success of this

research.

Radhwan Bin Hussin

January 2013

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ABSTRAK

Tesis ini, menjalankan penyelidikan berkenaan kecacatan yang terhasil pada

produk plastik didalam proses pengacuan suntikan. Semasa menghasilkan produk

menggunakan proses pengacuan suntikan, pelbagai kecacatan seperti melenting,

garis kimpal, pengecutan dan tanda tenggelam boleh berlaku. Satu set parameter

optimum pengacuan suntikan adalah sangat penting untuk ditentukan selepas

pelbagai ujian telah dibuat bagi mengurangkan dan mengawal kualiti kecacatan

produk acuan suntikan. Tujuan kajian ini adalah meminimumkan kecacatan

melenting dan pengecutan pada bahan polikarbonat (PC) termoplastik dan proses

simulasi pengacuan suntikan dengan menggunakan Moldflow Plastics Insight

Software (MPI). Cermin mata optik telah dipilih sebagai produk yang akan dikaji dan

model direkabentuk dengan menggunakan aplikasi UNIGRAPHIC NX 7.5.

Pendekatan berdasarkan Design of Experiment (Taguchi Method) telah dilaksanakan

untuk menganalisis dan mengoptimumkan parameter seperti suhu acuan, suhu

leburan, masa padatan, tekanan padatan, masa penyejukan, suhu penyejukan, dan

saiz pelari. Pelan eksperimen didapati dalam bentuk Orthogonal Arrays. Perisian

Minitab digunakan untuk merekabentuk eksperimen secara automatic dan

menganalisis keputusan dengan berdasarkan Design of Experiment (Taguchi Method)

bagi mencari satu set parameter terbaik terhadap plastik acuan suntikan.

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CONTENTS

CHAPTER TITLE PAGE DECLARATION ii

DEDICATION iii

ACKNOWLEDGEMENTS iv

ABSTRACT v

ABSTRAK vi

CONTENTS vii

LIST OF TABLES x

LIST OF FIGURES xii

LIST OF APPENDICES

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1 INTRODUCTION

1.1 Introduction to the Problem 2

1.2 Objective of Project 3

1.3 Scope of Project 3

1.4 Methodology of Study 4

1.5 Significant of finding 4

1.6 The Purpose and the Limit of This Study 5

1.7 Report Structure 5

1.8 Summaries 6

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2 LITERATURE REVIEW

2.1 Introduction 7

2.2 Injection Molding Process 9

2.2.1 Injection Molding Machine Component 10

2.2.1 Injection Molding Machine Parameter 15

2.2.1 Injection Mold Design 19

2.3 Computer Aided Design 26

2.4 Moldflow Plastics Insight Software (MPI) 27

2.5 Design of Experiment 29

2.5.1 Taguchi Method 30

2.5.2 The Orthogonal Array (OA) 31

2.5.3 Signal to Noise (S/N) Ratio 32

2.5.4 Measurable Characteristics 33

2.5.5 Analysis of Variance 34

3 METHODOLOGY

3.1 Research Methods and Procedures 35

3.2 Design of Optical Glasses in using Unigraphics NX7.5 37

3.3 Injection Mold Design 38

3.3.1 Prepare the Model 38

3.3.2 Refine Mesh Density 39

3.3.3 Gate Location 40

3.3.4 Design of Runner, Sprue and Gate 41

3.3.5 Design of Cooling System 42

3.4 Experimental Design 43

3.4.1 Create Taguchi Orthogonal Array 44

3.5 Analysis Implementation 47

3.6 Simulation Process 50

3.7 Conformation Test 50

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4 RESULTS AND DISCUSSION 4.1 Simulation Results 52

4.1.1 Summary of Result Respectively 55

4.2 Analysis of Results 57

4.2.1 Analysis Results for Warpage 57

4.2.2 Analysis Results for Shrinkage 60

4.3 Confirmation Tests 64

4.3.1 Recommended Setting Result 64

4.3.2 Confirmation Tests Result 66

4.3.3 Comparison of Test Results 67

5 CONCLUSION 5.1 Conclusions 68

5.2 Recommendations 71

REFERENCES 72

APPENDIX A 75

APPENDIX B 78

APPENDIX C 83

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LIST OF TABLES

TABLE NO TITLE PAGE

2.1 Advantages and disadvantages of injection molding process 10

2.2 Gating systems 20

2.3 Summary of gate types 20

2.4 Other kinds of defects on injection molding process 25

2.5 Summaries CAD vendors 27

2.6 3 Signal-to-Noise ratios of common interest for optimization 34

3.1 The process parameters and their levels 45

3.2 Orthogonal array L27 (37) 46

3.3 Noise factors and their levels 47

3.4 The Physical Properties of polycarbonates PC 47

3.5 Combination parameter for the control factor 48

4.1 Result analysis 1 and 2 53

4.2 Result analysis 3 and 4 54

4.3 Summary results of warpage 55

4.4 Summary results of shrinkage 56

4.5 Response Table for signal to noise ratio-warpage 57

4.6 Response Table for Means-warpage 58

4.7 Optimum setting Table for warpage 59

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4.8 ANOVA for warpage 60

4.9 Response Table for signal to noise ratio-Shrinkage 61

4.10 Response Table for Means-Shrinkage 61

4.11 Optimum setting Table for Shrinkage 62

4.12 ANOVA for shrinkage 63

4.13 Recommended Setting for warpage 65

4.14 Recommended Setting for Shrinkage 65

4.15 Confirmation test results for warpage 66

4.16 Confirmation test results for shrinkage 66

4.17 Comparison test results 67

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LIST OF FIGURES

FIGURE NO TITLE PAGE

2.1 Schematic of an injection molding machine 9

2.2 Reciprocating screw that features three zones 11

2.3 Exploded view of the A-side of an injection mold 13

2.4 Exploded view of the B-side of an injection mold 13

2.5 Exploded view of the ejector plate assembly of an injection mold 14

2.6 The categories of parameters 15

3.1 The overall research methodology 36

3.2 3D View of optical glass in Unigraphics NX 7.5 37

3.3 General dimensions of optical glasses 37

3.4 First step importing picture to MPI 38

3.5 Solid model before mesh process in MPI 38

3.6 Model after meshing process 39

3.7 Gating suitability 40.

3.8 Dimension of runner system 41

3.9 Location of gating system at model 42

3.10 A specific design of cooling systems 43

3.11 Selection of noise factors and control factor of injection molding 44

process.

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3.12 Parameter setting in moldflow plastics insight software 49

3.13 Model after analysis 49

3.14 The optimal conditions 50

4.1 Response diagram of S/N ratio for warpage 58

4.2 Response diagram of means for warpage 59

4.3 Response diagram of S/N ratio for shrinkage 61

4.4 Response diagram of means for Shrinkage 62

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LIST OF APPENDICES

APPENDIX TITLE PAGE

A1 Master Project planning 76

A2 The common cooling medium 76

A3 The average diameter of runner according to material being used 77

B1 The result conformation test of warpage analysis (A1) 79




B5 The result conformation test of Shrinkage analysis (A1) 81




C1 Technical Drawing 84

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CHAPTER 1

INTRODUCTION

In recent years, Plastic injection molding is one of the most important

polymer processing operations in the plastic industry and it is the fastest growing

major industries now days. Every year, plastic products increases rapidly for replace

product plastic with other material products to saving the manufacturing cost , as

well as make sure it works the same or better than the existing . It is a good situation

can be seen in the increase of percentage of plastics used in industry today’s. Mostly,

people are depending on plastic products to make a human life easier and simple.

Therefore plastic products play an important role in human life and are widely used.

Injection molding product has been used in the daily application such as for

household appliances, industry field and sport equipments because plastic materials

has low cost and light in weight compare to other material.

With this process, it has opened the door to applications never thought

possible before. These are emerging both as product innovations and as existing

products converted from materials such as metal, glass, wood or paper to plastics

for competitive and economic advantages.

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1.1 Introduction to the Problem

Nowadays, the design of plastics injection molding product becomes more

complicated and the requirement for quality characteristic is keep increase. Plastic

injection molding process produces various defects such as warpage, sink marks,

weld lines and shrinkage. Warpage and shrinkage is a common issue related with

injection molding process and shall be minimized. The defects of injection molding

process usually arise from several sources, which include the preprocessing

treatment of the plastic resin before the injection molding process, the selection of

the injection-molding machine, and the setting of the injection molding process

parameters.

The easiest way to do the set-up on the injection-molding machine is based

on the machine set-up operator or technician’s experience, or trial and error method.

This trial and error method is unacceptable because it is time consuming and not cost

effective. Some industries still using this method and produces so many products

abandoned in order to determine the most appropriate parameter. This method cannot

find the most appropriate parameters to reduce the defect of the product, so that

should provide some jigs to clamp the product after the injection molding process for

reducing the defect like warpage. Accordingly, it has increased the production cycle.

Therefore, using design of experiment for this study is to find the optimal

parameters to minimize defects produced after injection molding process that can be

increase productivity with save costs in manufacturing industries.

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1.2 Objective of Project

The objective of the study is:

i. To study the modeling/analysis of plastic injection molding parameters

with moldflow plastics insight software.

ii. To optimize the process parameters using Design of Experiment

(Taguchi Method).

1.3 Scope of the Project

The scope of the study for this project consists:

i. Defect warpage and shrinkage will be observed for the optimized

parameters.

ii. Parameters to be studied include mold temperature, melt temperature,

packing time, packing pressure, cooling time, cooling temperature, and

runner size.

iii. Moldflow plastics insight software and Design of experiment will be

employed.

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1.4 Methodology of Study

This research is divided into two parts. Part one is done in first semester and

part two is done in the second semester. The activities of part one consists of

literature review on plastic injection molding process and parameters, analyzing the

product including the consideration on mold temperature, melt temperature, packing

time, packing pressure, cooling time, cooling temperature, and runner size by using

MoldFlow software and collect the data. The product will be designed by using

Unigraphics NX7.5 software.

Then it is further continued part two with the study on optimization by using

Design of Experiment (Taguchi Method) of plastic defect on the machine parameter

which affects on the product. From Design of Experiment (Taguchi Method), it will

get the best parameters of the product.

1.5 Significance of Finding

The research will be fine the defect of parameters in injection molding

process for the Selected product. Hopefully at the end of this project, the research

will be:

i. Able to understand the parameters for injection molding process.

ii. Able to use Mold Flow software to analyze the defect in injection

molding process.

iii. Able to do the optimization by using Design of Experiment (Taguchi

Method) for the part selected and any parts in the future.

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1.6 The Purpose and the Limit of This Study

The main objective of this thesis is to study the modeling/optimization of

plastic injection molding parameters with combination of CAD and CAE on sport

equipment. DOE method was used to optimize the process parameters incorporated

with three levels in every parameter. Those parameters are mold temperature, melt

temperature, packing time, packing pressure, cooling time, cooling temperature, and

runner size. By doing this, hope to get a better product quality with fewer defects and

moreover, will affecting the cost of scrap productions. Furthermore, Moldflow

Plastic Insight software was used to simulate injection-molding process and show the

prediction of how large defects that were happen during process. There is warpage

and shrinkage defect that will become issue to be optimized.

1.7 Report Structure

This thesis is arranged by dividing into six chapters. It includes introduction,

literature review, methodology, results and discussion, conclusion and

recommendation. The contents of each chapter are briefly explained as follows:

Chapter 1: Introduction – overviews of hard coating research and several

studies related to this research were done. The scope of study and objectives

of the work are identified.

Chapter 2: Literature review –Literature review on injection molding

process, injection molding parameters, material to be used, Unigraphics

software, MoldFlow Software and Design Of Experiment (Taguchi Method).

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Chapter 3: Research methodology – The methodology of the project,

include the flow chart for the whole thing on how the study is done. Also,

contains brief explanations of the method to be used.

Chapter 4: Results and Discussion – Includes the experiment results from

MoldFlow Plastics Insight software analysis and result from Design of

Experiment (Taguchi Method). Discussion, Results represented by graph and

graphic image to provide understanding and easier analysis.

Chapter 5: Conclusion -The value of the project itself and the

recommendation for the same kind of project to be developed in the future

are determined in this chapter. Finally, the conclusion about the whole field

of study in the experiments, based from the objectives of the study.

1.8 Summary

In this chapter, the overview of the study such as, introduction to the research

area, objective of the study, scope of the study and methodology of the study and

also significance of findings is presented. The next chapter will discuss the literature

reviews on plastic injection process and parameters.

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Juliawati, A.B.S.Alias, Optimization of Warpage Defect in Injection

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the plastic injection molding. Materials and Design 30 2009: p. 367–375.

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injection molding using ANOVA, neural network model and genetic

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