OPTIMIZATION OF FEED SYSTEM DESIGN IN FAMILY MOULD USING

MOULD FLOW SIMULATION SOFTWARE

MOHD U'KASYAH BIN HASHIM

A thesis submitted is fulfillment of the requirements

for the award of the degree of

Bachelor of Manufacturing Engineering

Faculty of Manufacturing Engineering

UNIVERSITI MALAYSIA PAHANG

JUNE 2012PERPUSTAKAA.N .

UNIVERSfl1 MALAYSIA PAHANG

No. Perooh3n No. Panggilan

06737 0" Tarikh JU33

ç\ L-

vi'

ABSTRACT

Various problems have been found in the plastic injection industry recently. One of the

major obstacles is a balancing of gates and runners in a family mold due to lack of clear

understanding of the flow behavior of plastic in the mold resulting in overpacking, short

shot or any other defects on the parts. The objective of this research is to to compare

mould flow simulation software with actual injection molding and predict possibility of

injection molding defect before injection. 'The aim of our analysis is to provide a

simple experimental model simulation was performed. Different sizes of simple

geometric parts were selected as a case study for a family mold with two cavities.

Mould flow simulation software was employed to analyze the plastic feeding system

such as sprues, runners and gates. The simulation results were obtained as a useful

guideline for balancing of gate and runner system for a family mold. Consequently, a

numerical tool simulating plastic injection processes can assist mold designers to design

molds and to optimize the injection processes in order to avoid any defects such as fill

time, pressure, pressure at end of fill, volumetric shrinkage, pressure at V/P switchover,

temperature at flow front, sink mark index, weld lines and many more before

manufacturing the molds. After get result we chose the best and compare the actual after

injection.

vii'

ABSTRAK

Pelbagai masalah yang telah dijumpai dalam industri suntikan plastik baru-baru mi.

Salah satu halangan utama adalah pengimbangan pintu pagar dan pelari mengikut acuan

keluarga yang disebabkan kekurangan kefahaman yang jelas tentang kelakuan aliran

plastik mengikut acuan menyebabkan tembakan overpacking, pendek atau mana-mana

lain-lain kecacatan pada bahagian. Objektif kajian mi adalah untuk membandingkan

perisian simulasi aliran acuan dengan pengacuan suntikan sebenar dan meramalkan

kemungkinan kecacatan pengacuan suntikan sebelum suntikan. 'Tujuan analisis kami

adalah untuk menyediakan model simulasi eksperimen mudah dilakukan. Saiz yang

berlainan bahagian geometri mudah telah dipiih sebagai kajian kes untuk membentuk

keluarga dengan dua rongga. Perisian simulasi aliran Acuan telah digunakan untuk

menganalisis sistem memberi makan plastik seperti sprues, pelari dan pagar. Keputusan

simulasi telah diperolehi sebagai garis panduan yang berguna untuk mengimbangi

sistem pintu gerbang dan naib juara untuk membentuk sebuah keluarga. Akibatnya, alat

yang berangka simulasi proses suntikan plastik boleh membantu pereka acuan acuan

reka bentuk dan mengoptimumkan proses suntikan untuk mengelakkan sebarang

kecacatan seperti isimasa, tekanan, tekanan pada akbir pengecutan isi, isipadu, tekanan

di V / P peralihan, suhu di bahagian hadapan aliran, tenggelam indeks tanda, garisan

kimpalan dan banyak lagi sebelum pembuatan acuan. Selepas keputusan mendapatkan

kita memilih yang terbaik dan membandingkan sebenar selepas suntikan.

IA

TABLE OF CONTENT

Page

EXAMINER'S DECLARATION ii

SUPERVISOR'S DECLARATION

STUDENT DECLARATION iv

DEDICATION v

ACKNOWLEDGEMENTS vi

ABSTRACT vii

ABSTRAK viii

TABLE OF CONTENTS ix

LIST OF FIGURES xiii

LIST OF TABLES xv

LIST OF SYMBOLS xvi

LIST OF ABBREVIATIONS xvii

CHAPTER 1 INTRODUCTION

1.1 Introduction I

1.2 Problem Statement 2

1.3 Significant Study 3

1.4 Project Objectives 3

1.5 Scopes of The Project 3

CHAPTER 2 LITERATURE REVIEW

2.1 Introduction

2.2 Mold Flow Plastic Insight Software

2.3 Plastic simulation

2.4 Mesh Analysis

2.5 Flow Analysis

2.5.1 Advantages of Flow Analysis

2.6 Family Moulds

4

5

6

7

7

8

8

x

2.7 Governing Equations 10

2.8 Equipment 13

2.8.1 Injection Molding 13

2.8.2 Injection Unit 14

2.8.3 Moulds 15

2.8.4 Shrinkage and Warpage 19

CHAPTER 3 METHODOLOGY

3.1 Introduction 22

3.2 Method 22

3.3 Software 23

3.3.1 Blood Flow Properties 23

3.3.2 CATIA Software 24

3.3.3 Autodesk Mouldflow Plastic Insight Software (MPI 5.0) 24

3.4 Numerical Simulation 25

3.5 Steps Analysis 26

3.5.1 Design 27

3.5.2 Import Cad Model 27

3.5.3 Set the Mesh Density 28

3.5.4 Generate Mesh 28

3.5.5 Clean Up The Mesh 28

3.5.6 Select the Material 29

3.5.7 Select the Gate Location 29

3.5.8 Select the Molding Machine 29

3.5.9 Determine the Molding Conditions 29

3.5.10 Set the Analysis Parameters 30

3.5.11 Run the Analysis 30

3.5.12 Solve Filling Problems 30

3.5.13 Runners Balancing 31

3.5.14 Packing Profile Selection 31

3.6 Polymer 32

XI

3.6.1 Overview 32

3.7 Product Design And Insert Mould Design 34

3.7.1 Design of Types Bag Holder 34

3.8 Mould Design 35

Insert Cavity and Insert Core 36

3.9 Mould Base 38

CHAPTER 4 RESULTS AND DISCUSSION

4.1 Introduction 39

4.2 Mouldflow Setup Parameter 39

4.3 Feed System Setup 40

4.4 Result Discussion Of Simulation 42

4.4.1 Fill Time 42

4.4.2 Fill Time rate 43

4.4.3 Pressure 44

4.4.4 Pressure At End of Fill 45

4.4.5 Pressure at V/P switchover 46

4.2.6 Temperature At Flow Front 47

4.2.7 Sink Index 48

4.2.8 Weld line 49

4.5 Comparison Between Simulated and Actual Moulded Product 50

CHAPTER 5 CONCLUSION AND RECOMMENDATIONS

5.1 Introduction 51

5.2 Conclusions 51

5.3 Recommendation 54

XII

REFERENCES .55

APPENDICES

Al Gant Chart for FYP 1 56

A2 Gant Chart for FYP 2 57

B! Summary Result Analysis 1 58

Cl Result Analysis 2 73

C2 Result Analysis 3 74

C3 Result Analysis 4 75

C4 Result Analysis 5 76

Dl Machining Process 77

D2 Insert and Mould 78

D3 Application of actual product 79

LIST OF FIGURES

Figure No. Title Page

2.1 Balance runner 5

2.2 Some examples of possible cavity and runner layout design 9

alternatives of a family mould of four dissimilar parts.

2.3 Cross-sectional view of the flow front 10

2.4 Flow paths in unbalanced flow 10

2.5 Flow paths in balance flow 11

2.6 Plot of fill times at different thicknesses 12

2.7 An injection molding machine 13

2.8 Injection molding machine in plant environment 14

2.9 Reciprocating screw machine 15

2.10 Mould Parts 16

2.11 The molded system. 17

2.12 Hot runner system types: (a) the insulated hot runner, (b) the 18 internally heated hot-runner system, and (c) the externally heated hot-runner system

3.1 The Flow Diagram of the Project 25

3.2 The Step for Analysis Diagram 26

3.3 Bag holder 27

3.4 3D view of 2 design bag holder 34

3.5 General dimensions of bag holder 35

3.6 Insert cavity 36

3.7 Insert core 36

XIII

3.8 Cavity and core 37

3.9 insert cavity and insert core when assemble 37

3.10 Isometric view 38

3.11 front view and side view 38

4.1 Runner system with dimension 40

4.2 Fill Time for analysis 1 42

4.3 F ill time rate for analysis 1 43

4.4 Pressure for analysis 1 44

4.5 Pressure end of fill for analysis 1 45

4.6 Pressure at v/p switchover for analysis 1 46

4.7 Temperature at flow front for analysis 1 47

4.8 Sink index for analysis 1 48

4.9 weld line for analysis 1 49

4.10 Actual part bag holder fabricated from rapid prototyping 50 used in this study

4.11 Actual part bag holder developed in this study 51

4.12 Simulate model of bag holder using MPI software 51

4.13 Sink index area in simulate model for this study 52

4.14 Area sink mark at actual bag holder 52

4.15 Location of weld line in the simulated model carried out in 53 this study

4.16 The location of weld line (indicated by the weld line) 54

xiv

xv

LIST OF TABLES

Table No. Title Page

2.1 Advantages and disadvantages of hot-runner systems 18

2.2 Other kinds of defects on injection molding process. 21

3.1 Molding temperature for variation of polymer materials 33

4.1 Other paremeters' changes in these 5 different analysis 41

5.1 Summarization of product

52

5.2 Defect prediction before injection 53

LIST OF SYMBOLS

V Velocity

R, r Radius

r Density

T Temperature

11 Shear Viscosity

k Thermal conductivity

€ Strain

P Pressure

a Modulus of Elasticity

Cp Specific heat

D, d Diameter

C Celsius

V Volume

t Time

s second

v/p velocity/peresure

MPa Mega Pascal

xv

LIST OF ABBREAVIATION

MPI Mouldflow Plastic Insight

CAD Computer-Aided Design

CAM Computer-Aided Manufacturing

CAE Computer Aided Engineering

CNC Computer Numeric Control

FMLD Family Mould Layout Design

31) Three Dimensional

PP Polypropylene

PS Polystyrene

PE Polyethylene

PC Polycarbonate

PMMA Poly(rnethacrylic acid)

PA Polyacetylene

PVC Polyvinyl Chloride

PPS Polyphenylene Sulphide

LDPE Low-density Polyethylene

HDPE High-density Polyethylene

ABS Acrylonitrile Butadiene Styrene

HIPS High Impact Polystyrene

AS Acrylonitrile Styrene

PU Polyurethane

PBT Polybutylene Terephthalate

xvii

CHAPTER 1

INTRODUCTION

1.1 INTRODUCTION

In an age of globalization, the technology of the tool and die fabrication in plastic

injection is one of the world's fastest growing industries. Plastic is now used in almost

every application, ranging from household articles to space travel, from transportation to

packing, from medicine to toys, from bridge building to sports. Generally, injection

moulding is a process that forms the plastic into a desired shape by melting the plastic

material and forcing the plastic material under pressure into the mould cavity. The shape of

the plastic that is desired is achieved by cooling in thermoplastic or by chemical reaction

for thermosetting. (Source by Shamsuddin Sulaiman, Napsiah Ismail & A.M.S. Hamouda,

Design and Simulation of Plastic Injection Moulding Process. Department of Mechanical

and Manufacturing Engineering Universiti Putra Malaysia).

Mould design and fabrication is a costly and high technology process because it

uses science-based as mould flow plastic insight (MPI) software to analyse and simulate

the plastic parts, computer-aided design (CAD) software to design the complicated plastic

Product and computer-aided manufacturing (CAM) to do the programming fabrication to

run the computer numerical control (CNC) for milling or latch. Advances in computer

technology have led to an increasingly favorable power to cost ratio for computers. So this

advantageous and costly technology will improve productivity and process consistency.

Thus, for this fast growing industry, new technologies are vital to ensure that this

technology reaches perfection. So mould flow, plastic insight (MPI) is the assistant to

Process and calculate the plastic material flow inside the injection moulding.

I

2

1.1 PROBLEM STATEMENT

In the mould manufacturing nowadays, Family mould is still being used by some

companies especially when the production volume is low and tooling cost is an issue. One

of the above started reason is batch production that becoming common in manufacturing

today. Global market competition and customer demand had lead to shorter product

lifecycle complicated and quality product with competition price and the essence of right

time delivery to market.

Family mould is due to can save money on multiple part types. It consists of a

complete mold with a few or many different cavity inserts that runs as a single part each

cycle or more parts each cycle. Family molds are often utilized when two or more part

designs are similar but not identical, or if mold cost is a driving factor. Two different parts

can be produced from a single mold. This can save on time and expenses by sharing

common mold components such as the mold base, but also allows for a single mold setup.

Family molds are typically better suited for lower volume applications, and

automation may be necessary to separate pieces during or after production. They also have

the potential for greater downtime as repairs and modifications to a single part affect all the

components within the mold. Some of the benefits of a family mold are lost if the parts in

the mold are run in different resins. When designing plastic parts for the injection moulding

process, the important element to understand is how the plastic is filling in the mould. In

the mould injection filling phase, molten plastic is injected into the cavity until the cavity is

just filled. As plastic flows into the cavity, the plastic in contact with the mould wall

quickly freezes and this will create a frozen layer of plastic between the mould and the

molten plastic. The problem also can detect when use mould flow simulation, example

balance flow, clamping force, feed system not balance. In this experiment can know how to

compare from data Autodesk mould flow inside with actual while injection molding.

3

1.2 SIGNIFICANT OF STUDY

There are few significances of this study when objectives have been achieved as

follow:

L We can use simulation software before produce product in injection molding.

Comparison in software analysis.

ii. We can study design balance flow analysis in family mould and optimization

of feed system design.

13 PROJECT OBJECTIVES

The objectives of this study are:

i. To compare mould flow simulation software with actual injection molding

ii. To predict possibility of injection molding defect before injection.

iii. To apply knowledge of machining process into practical way.

1.4 SCOPES OF THE PROJECT

The scopes of this project are limited to:

L Study on feed system design for the gate and runner modeling-critical to

achieving accurate results.

ii. Study on the Optimization of the design to anticipate any molding problems

before the tool is constructed.

CHAPTER 2

LITERATURE REVIEW

2.1 INTRODUCTION

In this research, will discuss about the mould flow simulation software

Mould flow Plastic Insight (MPI). MPI is used to study the effects of feed system

design in family mould. There are a number of factors to consider when designing

the feed system, including the gate locations, the number of cavities, the shape of

the runner system components, and flow balance.

The first step in designing the feed system is to determine the gate locations

for each part in the mold. The rest of the components will fit into place depending

upon each gate location. The objective when designing the feed system is to design

it with balanced flow so that each part in the mold fills at the same rate. The

creation of a well-balanced feed system requires careful consideration the following

elements: [1]

• Single-cavity, multi-cavity, or family mold

• Cavity layout

• Location of the sprue

• Runner system layout

• Shape of the sprue, runners, and gates

4

5

In general, make runners as short as possible, with the lowest possible shot

weight. In the following diagram, the flow length for every part is the same. This is

a naturally balanced runner system [1] . Balance runner as shown in the Figure 2.1

Figure. 2.1: Balance runner

The balancing of the runner system is an iterative, trial-and-error process,

relying heavily on the knowledge and experience of the mold designer. It is

generally a three phase process comprising filling, packing and cooling phases. Its

popularity is typified by the numerous products produced in this way at the present

time by L.W. Scow, Y.C. Lam [2]. These analysis programs can be used by a mold

designer to simulate and balance the runner system of the mold. The goal during

runner balancing is to vary the diameters of the runner segments such that all the

cavities fill at the same time and pressure by Ivan W.M. Chan Martyn Pinfold

C.K. Kwong W.H. Szeto [3].

2.2 MOLD FLOW PLASTIC INSIGHT SOFTWARE

Moldilow Plastic Insight software was developed by Mold flow. Corporation

to aid designers in the plastic industries to:

• reduce product development time and rework, hence decreasing

overall costs

6

reduce manufacturing cycle time;

• improve product design and foresee any problems related to product

manufacturability.

• provide options for various processing parameters and material for

both plastic and composite product.

The software provides simulation modules for various processes such as:

• thermoplastic injection molding;

• gas assisted injection molding

• co-injection molding

• injection-compression molding

• reaction injection molding

• microchip encapsulation

• underfihl encapsulation (flip chip)

Thermoplastic injection molding simulation involves solving the governing

equation of mass, momentum, and energy numerically over the physical domain.

The numerical implementation involves discretizing the physical domain into a

number of sub domains, or elements. The dependent variables (velocity, pressure

and temperature) are approximated within each element.

2.3 PLASTIC SIMULATION

Simulation tools used range from simple, CAD centric filling and gating

studies, to product optimization, highly complex warp predictions, and visco

elasticity load cases. Presented below are some examples of mold flow projects,

many were performed in concert with a design optimization effort prior to tooling

release. There are two major benefits to performing a serious mold flow study prior

to part release.

Optimization of the design to anticipate any molding problems before the

tool is constructed. Capture of the "as-molded" structural properties of the part not

as designed, but as manufactured, enabling highly accurate FEA of the part.

The bottom line-these tools and techniques reduce tool validation times,

decrease or eliminate unanticipated part failures, and provide indicators for

dimensional stability before releasing the part.

Formally the domain of the tool shop, the value of performing these types of

studies as a component of the design and part engineering process is well

established. Review the examples below and see how your project can benefit from

using advanced mold flow simulation.

2.4 MESH ANALYSIS

There are two main prerequisites that must be specified in the model in order

to run a flow analysis. They are:

(i) A meshed part model;

(ii) Specifying injection nodes in a boundary condition file.

There are three main types of mesh provided by this software; midplane,

surface (fusion) and volume (31)) mesh. The clutch pedal model is drawn using the

software attributes and meshed using a midplane mesh. A midplane mesh consists

of three nodded triangular elements located at the half thickness of the part surface.

By stating the thickness of the part, the two-dimensional midplane mesh represents

the solid model during the molding analysis.

2.5 FLOW ANALYSIS

Mould Flow analysis is recommended be performed on this project. This is

because it will assist in identifying potential problems in the molding process and

allow to vary gate location, process conditions, and/or geometry to predict problems

8

and determine solutions. A filling analysis will allow the make these changes before

the tool is cut and will reduce potential costs associated with reworking a tool. The

field of flow analysis has gained increasing importance in injection molding. Flow

analysis has provided rational solution to many of the hard-to-understand effect that

cause problem in he molding process. These effects have including warping,

molded-in stress, excessive fill pressure, part flashing and other.

2.5.1 Advantages of Flow Analysis

The CAE simulation provides engineers, designers, moulders with a visual

and numerical feedback about what actually happens inside the mould cavity during

the injection moulding process.

2.6 FAMILY MOULDS

Cold runner family moulds are widely used in some industries, such as toys

and domestic products, because it is an economical method to produce plastic parts

of different shapes of the same plastic material with a relatively low-dimensional

accuracy requirement for a small-to-medium production volume.

The cost estimation for quotation and themoulding performance of a family

mould are highly dependent on a family mould layout design (FMLD) decision

made during the early mould design phase. It is because FMLD determines many

key design factors such as cavity layout design, runner layout design, mould base

selection, cooling system design and so forth by Ivan W.M. Chan Martyn Pinfold

C.K. Kwong W.H. Szeto [3]

For example, a simple family mould of four dissimilar parts already involves

a number of possible cavity layout and runner layout design alternatives can be see

in Figure 8. Design alternative (a) seems to be the best one because of its compact

and balanced layout, but it requires two individual sliders for part 2 and part 3.

Design alternative (h) can save cost by combining the two individual sliders into

one but at the expense of an unbalanced layout and larger mould base. In some

cases, a larger mould base is not preferable or even not allowed due to the

insufficient space of the mould platen of a customer's molding machine. Layout

possible cavity and runner respectively as shown in the Figure 2.2 by Ivan W.M.

Chan Martyn Pinfold C.K. Kwong W.H. Szeto [3].

cavity mould insert

1 E slider

a runner

0

U!.

U

0

onw

Figure 2.2: Some examples of possible cavity and runner layout design

alternatives of a family mould of four dissimilar parts

(Source by Ivan W.M. Chan Martyn Pinfold • C.K. Kwong W.H. Szeto, A review of research, commercial software packages and patents on family mould layout design

automation and optimisation, hit J Adv Manuf Technol 2011)

10

Simulation software solves the governing equation of mass,

momentum,band energy of injection moulding process numerically. Simulation of

filling and packing phase of injection moulding process depends on accurate

characterization of the material properties by Iwan Halim Sahputra [7]

2.7 GOVERNING EQUATIONS

Plastic flow in the filling phase is like flow between two plates separated by

a small distance. This is well modelled by the Hele-Shaw approximation in general

by L.W. Scow, Y.C. Lam [2]. Assuming an incompressible, generalized, non-

Newtonian fluid, the equations for the filling phase can be written as:

Frozen Layer I I ow waN

Z

WK Front

— - — - — - — \---- 12h

Figure 2.3: Cross-sectional view of the flow front

IlFiow Front I

Figure 2.4: Flow paths in unbalanced flow

Continuity equation:

(1)

& —+--±—=o ox cij Oz

Momentum Equation:

Op 0 ( iiu

Ox TZ

ap (7 Ov

- Oz Oz

Energy Equation:

(LaTtOT OT\ 02T

pC1 + u---± 'jy- +k 0z2

where (x, y, z) are the Cartesian coordinates and (u, v, w) are the velocity

components, respectively. T is the temperature, p the pressure, r is the density, Cp is

the specific heat and k is the thermal conductivity of the material whilst q is the

shear viscosity where the shear rate y is:

(4)

F(Ly+\zJ \Oz

Following the treatment by Kennedy [5], the continuity and momentum

equations can be combined to yield:

(5)

11

(2)

(3)

- 0X \, aX j aj

(sip)

12

Where

Flow Pethsl

Figure 2.5: Flow paths in balance flow

Plot of fill time vs thickness 1.6 1.4 1.2

U a, a,

a,

0.4

00 0.5 1 1.5

lIt(mm-1)

Figure 2.6: Plot of fill times at different thicknesses.

(6)

s= I (12)dz