UNIVERSITI TEKNIKAL MALAYSIA MELAKA

OPTIMIZATION OF INJECTION MOLDING PROCESS ON

NAME TAG PLASTIC PRODUCT

This report is submitted in accordance with the requirement of the Universiti

Teknikal Malaysia Melaka (UTeM) for the Bachelor of Manufacturing Engineering

Technology (Product Design) with Honours.

by

STUDENT NAME: LIM CUI FEN

MATRIX NUMBER: B 071310502

IC NUMBER: 930512-02-5764

FACULTY OF ENGINEERING TECHNOLOGY

2016

UNIVERSITI TEKNIKAL MALAYSIA MELAKA

BORANG PENGESAHAN STATUS LAPORAN PROJEK SARJANA MUDA

TAJUK: Optimization of Injection Moulding process on Name Tag Plastic Product SESI PENGAJIAN: 2016/17 Semester 1 Saya LIM CUI FEN Mengaku membenarkan Laporan PSM ini disimpan di Perpustakaan Universiti Teknikal Malaysia Melaka (UTeM) dengan syarat-syarat kegunaan seperti berikut: 1. Laporan PSM adalah hak milik Universiti Teknikal Malaysia Melaka dan penulis. 2. Perpustakaan Universiti Teknikal Malaysia Melaka dibenarkan membuat salinan

untuk tujuan pengajian sahaja dengan izin penulis. 3. Perpustakaan dibenarkan membuat salinan laporan PSM ini sebagai bahan

pertukaran antara institusi pengajian tinggi. 4. **Sila tandakan ( )

SULIT

TERHAD

TIDAK TERHAD

(Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia sebagaimana yang termaktub dalam AKTA RAHSIA RASMI 1972)

(Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi / badan di mana penyelidikan dijalankan)

AlamatTetap: 62A, Taman Lam Sun,

05200 Alor Setar,

Kedah Darul Aman. Tarikh: _____________________

Disahkanoleh:

Cop Rasmi: Tarikh: _______________________

** Jika Laporan PSM ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi berkenaan dengan menyatakan sekali sebab dan tempoh laporan PSM ini perlu dikelaskan sebagai SULIT atau TERHAD.

DECLARATION

I hereby, declared this report entitled “Optimization Of Injection Molding Process On

Name Tag Plastic Product” is the results of my own research except as cited in

references.

Signature : …………………………………………

Author’s Name : LIM CUI FEN

Date : 30 DECEMBER 2016

APPROVAL

This report is submitted to the Faculty of Engineering Technology of UTeM as a partial

fulfilment of the requirements for the degree of Bachelor of Manufacturing Engineering

Technology (Product Design) with Honours. The member of the supervisory is as

follow:

………………………………..

(Project Supervisor)

i

ABSTRAK

Proses pengacuan suntikan adalah satu proses yang digunakan secara meluas

untuk pembuatan kompleks berbentuk produk polimer. Proses pengacuan suntikan

terdiri daripada empat peringkat utama: proses plastifikasi, proses suntikan, proses pek

& tahan dan proses pelemparan. Selepas proses pelemparan, menyedari bahawa dimensi

bahagian adalah berbeza dari dimensi acuan yang dikehendaki, saiz produk telah

menjadi lebih kecil. Pengecutan adalah satu fenomena yang berlaku semasa pemejalan

bahan plastik lebur, tetapi ia juga boleh menjadi masalah utama yang sering dihadapi

oleh industri plastik jika ia adalah berlebihan disebabkan oleh faktor-faktor proses

parameter tanpa pengoptimuman. Kajian ini telah dibangunkan untuk menentukan faktor

utama yang menjejaskan sebahagian pengecutan, dan juga untuk mengoptimumkan

faktor proses parameter untuk produk tag nama. Faktor-faktor yang terlibat dalam kajian

ini ialah Tekanan Suntikan, Tekanan Ketahanan, Masa Ketahanan dan Masa Penyejukan.

Bahan yang dipilih untuk kajian ini adalah Acrylonitrile Butadiene Styrene (ABS) bahan

plastik. Kajian ini telah direka dengan menggunakan kaedah Taguchi, pendekatan

berstruktur yang biasa digunakan untuk menentukan kombinasi input yang "terbaik"

untuk menghasilkan satu produk plastik. Selepas menentukan keadaan operasi bagi

setiap parameter dan tahap (minimum, semasa dan maksimum), sebuah ortogon Array

(OA) yang sesuai telah dipilih untuk menghasilkan bilangan minimum percubaan untuk

menganggarkan kesan utama. 9 ujian telah dijalankan dan 10 sampel telah diambil dari

setiap percubaan. Pemeriksaan dimensi telah dibuat dengan menggunakan Mesin

Pengukuran Koordinat (CMM), untuk mendapatkan nilai purata tepat untuk mengira

nilai pengecutan. Nilai pengecutan digunakan untuk mencari Nisbah Isyarat-Hingar (SN)

dengan menggunakan Minitab, plot kesan utama bagi nilai purata dan nisbah SN telah

diperhatikan. Hasil kajian menunjukkan hubungan antara nisbah SN dan nilai

ii

pengecutan. Satu set faktor proses parameter yang telah dioptimumkan pada akhir

pengajian ini.

iii

ABSTRACT

Injection moulding is a widely used process for manufacturing complex shaped

polymer products. An injection moulding process consists of four main stages:

plastification, injection, pack & hold, and ejection. After ejection, noticed that the

dimension of the part is different from the desired mould dimension, the part size

becomes smaller. Shrinkage is a phenomenon which occurs during the solidification of

molten plastic material, but it can also be a main problem that often faced by the plastic

industry if it is excessive due to the process parameter factors without optimization. This

study was developed to determine the significant factor affecting the part shrinkage, and

also to optimize the process parameter factors for name tag product. The factors which

involved in this study were Injection Pressure, Holding Pressure, Holding Time and

Cooling Time. The selected material for this study was Acrylonitrile Butadiene Styrene

(ABS) plastic material. The experiments were designed by using Taguchi method, a

structured approach which commonly used for determining the “best” combination of

inputs to produce a plastic product. After determining the operating conditions for each

parameter and levels (minimum, current and maximum), a proper Orthogonal Array (OA)

was selected to create the minimum number of trials to estimate the main effects. The 9

trials were conducted and 10 samples were collected from each trial. The dimension

inspection were done by using Coordinate Measuring Machine (CMM), in order to obtain

the average value accurately in order to calculate the shrinkage value. The shrinkage

values were used to find the Signal-to-Noise (SN) ratios using Minitab software, the main

effect plots for means and SN ratios were observed. The results showed the relationship

between the SN ratios and the shrinkage value (means). A set of optimized process

parameter factors were obtained at the end of study.

iv

DEDICATION

This thesis is dedicated to my beloved family, my supervisor En Salleh bin Aboo Hassan

and all my fellow friends for their guidance and help to complete the Final Year Project

successfully.

v

vi

ACKNOWLEDGEMENT

Firstly, I would like to express my sincere appreciation to my supervisor, Encik

Salleh bin Aboo Hassan for his guidance, patience and encouragement. Thanks for

spending your precious time to teach me and guide me for the project. A special thank to

my friend, Ivy King Chien Chien who always helped me, guided me and supported me

all the time although she was also busy in her final year project. Without Encik Salleh

and Ivy, I would never able to complete this project on time.

I would like to express my gratitude to my parents and my family for giving me

support and encouragement. Not to forget my fellow friends who always support me

when I faced difficulties and problems. I am also thanks to the lecturers and technicians

who had borrowed me the machine instruments and laboratories, and guided me while

doing the experiments for the project.

vii

TABLE OF CONTENT

Abstrak i

Abstract iii

Dedication iv

Acknowledgement v

Table of Content vi

List of Tables ix

List of Figures x

List of Abbreviations, Symbols and Nomenclatures xii

CHAPTER 1: INTRODUCTION 1

1.0 Overview 1

1.1 Introduction 1

1.2 Project Background 4

1.3 Problem Statement 5

1.4 Research Objectives 5

1.5 Scope 5

CHAPTER 2: LITERATURE REVIEW 7

2.0 Introduction 7

2.1 History of Injection Moulding 7

2.2 Injection Moulding Process 10

2.2.1 Plastification Stage 11

2.2.2 Injection Stage 13

2.2.3 Packing or Cooling Stage 14

viii

2.2.4 Ejection Stage 14

2.3 Cold Runner VS Hot Runner 14

2.3.1 Cold Runner 15

2.3.2 Hot Runner 16

2.4 Defects in Injection Moulding process 17

2.4.1 Sink Mark 17

2.4.2 Flash 18

2.4.3 Short Shot 19

2.4.4 Gate Blush 19

2.4.5 Jetting 20

2.4.6 Weld lines 21

2.4.7 Vacuum Voids 21

2.4.8 Splay 22

2.4.9 Warpage 23

2.4.10 Burn Marks 23

2.5 Design of Experiment (DOE) 24

2.5.1 Taguchi Method 25

2.6 Plastic Materials 27

2.6.1 Acrylonitrile Butadiene Styrene (ABS) 27

2.7 Shrinkage 29

CHAPTER 3: METHODOLOGY 31

3.0 Introduction 31

3.1 Flow Chart 31

3.1.1 Planning of Study 33

3.1.2 Define Input Parameter and Variable 33

3.1.3 Apply Taguchi Method (DOE) 35

3.1.4 Injection Moulding Experiment 38

ix

3.1.5 Dimension Inspection 38

3.1.6 Data Collection & Analysis 40

3.1.7 Results & Discussion 41

3.1.8 Conclusion & Recommendation 41

3.2 Gantt Chart 41

CHAPTER 4: RESULT & DISCUSSION 43

4.0 Introduction 43

4.1 Operating Conditions for Each Parameter and Levels 43

4.2 Orthogonal Array by Minitab Software 47

4.3 Data Collection 48

4.3.1 Mean and Shrinkage Values 48

4.4 Data Analysis 51

4.4.1 Means and Signal-to-Noise ratios (SNR) 52

4.4.2 Analyzing the Relationship Between Means & SN Ratios 53

4.4.3 Optimizing the Process Parameters 54

4.4.4 Predicted Value 55

CHAPTER 5: CONCLUSION & FUTURE WORK 56

5.0 Introduction 56

5.1 Summary 56

5.2 Achievement of Research Objectives 57

5.3 Problems Encountered 58

5.4 Future Work Recommendation 58

x

LIST OF TABLES

1.1: Overview of Injection Moulding Process 2

2.1: General Properties of ABS. 28

2.2: Processing Characteristics of ABS 28

2.3: Moulding Shrinkage For Each Plastic Materials 29

3.1: Process Parameters of Injection Moulding Machine 34

4.1: Operating Conditions for Each Parameter and Levels 43

4.2: Uncoded L9 orthogonal array. 47

4.3: Sample Data. 49

4.4: Means and SNR values obtained from Taguchi Analysis from Minitab. 52

4.5: The Optimized Process Parameter. 54

5.1: The Optimized Process Parameter. 58

xi

LIST OF FIGURES

1.1: Injection Moulding Machine Overview. 3

1.2: Plastic Pellets for Injection Moulding Process. 3

2.1: Patent Drawings for Henry Injection Moulding Machine 8

2.2: Drawings for Willert Reciprocating Injection Moulding Machine. 9

2.3: Injection Moulding Machine 10

2.4: Diagram of Injection Moulding Process. 10

2.5: Structure of Injection Moulding Machine. 12

2.6: Hopper dryer. 12

2.7: Reciprocating Screw of Injection Moulding Machine. 12

2.8: Flights of Reciprocating Screw. 13

2.9: Check Ring and Thrust Ring. 13

2.10: Two-Plates Mould for Cold Runner. 15

2.11: Three-Plates Mould for Cold Runner. 16

2.12: Hot Runner Moulding System 17

2.13: Sink Mark Defect Sample. 18

2.14: Flash Mark Defect Sample. 18

2.15: Short Shot Defect Sample. 19

2.16: Gate Blush Defect Sample. 20

2.17: Jetting. 20

2.18: Weld Lines Defect Sample. 21

2.19: Voids Defect Sample. 22

2.20: Splay Marks Defect Sample. 22

2.21: Warpage Defect Sample. 23

2.22: Burn Marks Defect Sample. 24

2.23: Flow Chart of a DOE. 25

2.24: Ishikawa Diagram of Injection Moulding’s Process Parameters. 26

xii

3.1: Flow Chart of Research Methodology 32

3.2: ZHAFIR Plastic Machinery VE1200 II Injection Moulding Machine 34

3.3: Taguchi Design of Experiment (DOE) in MINITAB V6 Software. 36

3.4: The Taguchi Design with 3-Level Design and 4 Factors in MINITAB V6 software.

36

3.5: L9 Taguchi Design. 37

3.6: L9 Taguchi Design with Four Factors. 37

3.7: A Sample Product of the Experiment (Name Tag). 38

3.8: CONTURA G2 Coordinate Measuring Machine 39

3.9: UTeM’s Name Tag Product. 39

4.1: Short Shot Defect Sample. 44

4.2: Sink Mark Defect Sample. 44

4.3: Acceptable Sink Mark Sample. 45

4.4: Overpacked Samples due to Overpack Pressure. 45

4.5: Overpacked Part Stuck at the Mould. 46

4.6: Splay Defect Sample. 46

4.7: Coded L9 Orthogonal Array. 47

4.8: MINITAB V6 Software Data Analysis. 51

4.9: Taguchi Analysis Shrinkage versus IP, HP, HT, CT. 52

4.10: Main Effect Plot for Means. 53

4.11: Main Effect Plot for SN Ratios. 53

4.12: Predicted Values. 55

xiii

LIST OF ABBREVIATIONS, SYMBOLS AND

NOMENCLATURE

ABS Acrylonitrile-Butadiene-Styrene

ANOVA Analysis of Variance

CAB Cellulose Acetate Butyrate

CMM Coordinate Measuring Machine

DOE Design of Experiment

GF Glass Fiber

HDPE High-Density Polyethylene

LDPE Low-Density Polyethylene

OA Orthogonal Array

OAPEC Organization of Arab Petroleum Exporting Countries

PBT Polybutylene Terephthalate

PC Polycarbonate

PEEK Polyetheretherketone

PET Polyethylene Terephthalate

PPO Polyphenylene Oxide

PVC Polyvinyl Chloride

PVC-P Plasticized Polyvinyl Chloride

PVC-U Polyvinyl Chloride Unplasticized

SAN Styrene Acrylonitrile

SN ratio Signal-to-Noise ratio

TPE Thermoplastic Elastomers

1

CHAPTER 1 INTRODUCTION

1.0 Overview

This chapter explained about the basic knowledge of injection moulding process

and project title. Besides that, this chapter also described the project background, the

problem statement, objectives and the scope of this study.

1.1 Introduction

In the current market, there are many products made from plastic due to the

inexpensive price and attractive appearance. These plastic products were made by using

the technique of injection moulding process. Injection moulding is a manufacturing

process which commonly applied in industry field. It is a process of fabricating thin-wall

plastic products by injecting the molten plastic material into a mould, then ejected the

plastic products from the mould after cooling down. The shape of the plastic product can

be simple or complex, it also can be flexible or hard, thick or thin, and the size will not

be a problem for the injection moulding process. To set up a mould, it can take few

minutes or hours to maintain the process in stable. Typically, the cycle time for injection

moulding process will be taken only a few seconds or few minutes to produce one part.

The injection moulding machine consists of three main parts, they are injection unit, the

mould assembly and the clamping unit. The injection moulding process consists of four

main steps to complete one cycle of a production; the following table describes an

overview of the injection moulding process:

2

Table 1.1: Overview of Injection Moulding Process

Step 1

The plastic pellets (raw materials) are fed

into the barrel through a hopper. The

pellets are then transported forward when

the reciprocating screw is turning.

Step 2

The plastic pellets are melted by the

external pressure from the narrow space in

barrel, the friction inside the barrel and

the additional heat from the heater bands

which are surrounded the barrel. The

molten material flow into the nozzle, the

screw is then pushed forward to inject the

molten material into the mould cavity.

Step 3

The reciprocating screw holds and pack s

the molten material in the time set in order

to ensure the molten part was completely

solidified when the mould opens. The

cooling process is then proceed when the

holding time ends.

Step 4

After cooling process, the injected

material is fully solidified. The mould

opens eject the product by using the

ejector pins. One cycle of production

completes and repeats to produce the next

product.

There are various types of plastic materials used in the injection moulding

process, such as Polypropylene, Polystyrene, Polyethylene and other plastic materials.

Acrylonitrile-Butadiene-Styrene (ABS) (C8H8)x·(C4H6)y·(C3H3N)z) is one of the

popular amorphous thermoplastic which is commonly used in injection moulding

3

process. It is opaque, high resist to heat and chemicals, and even able to maintain high

durability at low temperature. Each material has different physical and chemical

properties which may affect the setting of process parameters in an injection moulding

machine. The process parameters such as mould temperature, injection pressure and

injection speed. Therefore, the process parameters are needed to be optimized based on

the material properties in order to produce a part with good quality.

Figure 1.1: Injection Moulding Machine Overview.

Figure 1.2: Plastic Pellets for Injection Moulding Process.

4

1.2 Project Background

Injection moulding process is a manufacturing process which can be applied by

using different materials such as glasses, metals, thermoplastic and thermosetting plastic.

Plastic injection moulding is the most common mass production process due to the low

cost materials used in that process. However, different plastic materials have the

different properties such as melting point, heat resistance, crystalline percentage and

others, which are required to take into consideration when running an injection moulding

process. This is because these properties will cause the occurs of defect if the injection

moulding process parameters are not optimized. The main problem that usually faced by

injection moulding process is shrinkage problem. Shrinkage is a phenomenon which

occurs during the solidification of molten material, as the dimensions of solidified part is

smaller than the size of mould cavity. This phenomenon could affect the product quality

if its percentage value is too high when the injection moulding is not optimized. An

excessive shrinkage can be detected from the warpage of the plastic product. In order to

minimize the shrinkage and warpage problems, researchers had contributed several

methods for the improvement. They had applied Taguchi Method and Signal-to-Noise

ratio to obtain the optimized process parameters. Taguchi Method was developed by

Dr.Genichi Taguchi, a Japanese engineer of Nippon Telephones and Telegraph

Company. This method applies a set of Orthogonal Arrays in order to set the minimum

experiment to be conducted, which could provide the most information of all the factors

that affect the performance parameter. While Signal-to-Noise ratios, a log function of

desired outputs will be applied to analyse the experimental and also to predict the

optimum results.

5

1.3 Problem Statement

The reason for this study is to address the need for controlling and minimize the

part of shrinkage formation in plastic materials for name tag product. Shrinkage is a

major problem when dealing with plastic injection moulding. Shrinkage could affect the

quality of moulded product. In this shrinkage study, we focused only on the ABS plastic

shrinkage problem which could be affected by many factors which could caused lower

quality of product in terms of dimension and well-finished surfaces. There were many

process factors that were required to be considered during an injection moulding process,

such as barrel temperature, mould temperature, injection speed, holding pressure and

more. These factors were analysed and optimized in order to produce a good quality

with less shrinkage moulded part.

1.4 Research Objectives

The objectives of this research study are:

i. To determine the significant factors affecting the part shrinkage.

ii. To optimize the process parameter factors for name tag product.

1.5 Scope

For the purpose of addressing the need to control and minimize the part of

shrinkage formation, we were only focused on shrinkage problem of one product, that

was UTeM name tag holder. The main process that involved in this study was the

injection moulding process, there was no other additional process involved in this study.

An electrical injection moulding machine (ZHAFIR Plastic Machinery VE1200 ton) was

used along this project to evaluate the shrinkage problem study. ABS (Acrylonitrile

Butadiene Styrene) was the only selected plastic material and it was evaluated for this

study. In order to ease the process, Taguchi Method was applied as Design of

6

Experiment (DOE) for this study for analysing the data observed. The dimensions of the

name tag holder such as length was recorded and also been measured for the calculation

of the product’s shrinkage percentage. To measure the dimensions precisely,

CONTURA G2 Coordinate Measuring Machine (CMM) was used for the measuring

process along this study.

7

CHAPTER 2 LITERATURE REVIEW

2.0 Introduction

This chapter had covered the literature review of the project study. In this chapter,

the literature review had introduced about the history of injection moulding, and also

reviewed the topics such as injection moulding process, plastic defects, plastic material,

Taguchi method and part shrinkage.

2.1 History of Injection Moulding

Injection moulding was a great invention for the human being to make many

kinds of product. Reviewing the history, it was started with Jons Jacob Berzelius, who

generated the first condensation polymer – polyester. In 1861, a British named

Alexander Parkes invented the first profitable plastic, he called it “Parkesine”, and also

demostrated it at 1862 International Exhibition in London. John Wesley Hyatt, an

American inventor, he had combined the cellulose nitrate and camphor for the purpose

of replacing the ivory in a billiard ball, a plastic material named “Celluloid” was born in

the year 1868. After four years, John Wesley Hyatt and his brother Isaiah had patented

the first injection moulding machine. People had described that the working of this first

injection moulding machine just like a hypodermic needle because a plunger was used to

inject the material.In 1909, a type of plastic called phenolformaldehyde plastic was

discovered by Leo Hendrik from Belgium. This substance was first controlled by Leo

and became usable on a large scale. During the 1930s, the major vinyl thermoplastics

such as polystyrene, PVC and polyolefins, were in the initial development stage. In 1938,