i optimization of molding parameter effect to...
Post on 20-Mar-2020
0 Views
Preview:
TRANSCRIPT
i
OPTIMIZATION OF MOLDING PARAMETER EFFECT TO WARPAGE AND
SHRINKAGE BASED ON PLASTIC FLOW SIMULATION SOFTWARE: HAND
PHONE CASING
MOHD NORHAFIZI BIN ROHAIZAT
A report submitted in partial fulfilment of
The requirements for the award of the degree of
Bachelor of Mechanical Engineering with Manufacturing
Faculty of Mechanical Engineering
UNIVERSITI MALAYSIA PAHANG
DECEMBER 2010
ii
UNIVERSITI MALAYSIA PAHANG
FACULTY OF MECHANICAL ENGINEERING
We certify that the project entitled “Optimization of Molding Parameter Effect to Warpage
and shrinkage based on Plastic Flow Simulation Software: Hand Phone Casing” is written
by Mohd Norhafizi Bin Rohaizat. We have examined the final copy of this project and in
our opinion; it is fully adequate in terms of scope and quality for the award of the degree of
Bachelor of Engineering. We herewith recommend that it be accepted in partial fulfilment
of the requirements for the degree of Bachelor of Mechanical Engineering with
Manufacturing Engineering.
Examiner Signature
iii
SUPERVISOR’S DECLARATION
I hereby declare that I have checked this project and in my opinion, this project is adequate
in terms of scope and quality for the award of the degree of Bachelor of Mechanical
Engineering with Manufacturing Engineering.
Signature : ..................................
Name of Supervisor : Mr Mohd Reza Zalani Bin Mohd Suffian
Position : Lecturer Faculty of Mechanical
Engineering Universiti Malaysia Pahang
Date : .................................
iv
STUDENT’S DECLARATION
I hereby declare that the work in this project is my own except for quotations and
summaries which have been duly acknowledged. The project has not been accepted for any
degree and is not concurrently submitted for award of other degree.
Signature : ................................
Name : MOHD NORHAFIZI BIN ROHAIZAT
ID Number: ME07036
Date : ...............................
vi
ACKNOWLEDGEMENTS
First of all, thanks to ALLAH SWT for giving me the strength and the chances in
completing this first Final Year Project. In preparing this thesis, I was in contact with many
people, researchers, academicians, and practitioners. They have contributed towards my
understanding and thoughts.
In particular, I wish to express my sincere appreciation to my previous thesis
supervisor, Mrs Siti Haryani Binti Tomadi for her encouragement, guidance, critics and
friendship in order to finish my final year project. I am also very thankful to all lecturers in
Faculty of Mechanical Engineering for their guidance, advices and motivation. The credit
also goes to all lecturers, tutors, teaching engineers (JP) especially Mr Imran and assistant
teaching engineers (PJP), Mr Faizul for helping me. Without their continued support and
interest, this thesis would not have been the same as presented here.
I am also indebted to Universiti Malaysia Pahang for funding my degree study. My
coursemates should also be recognized for their support. My sincere appreciation also
extends to all my colleagues and others who have provided assistance at various occasions.
Their views and tips are useful indeed. Unfortunately, it is not possible to list all of them in
this limited space. I am grateful to all my family members.
Finally, I would like to thanks my family especially my parent for their constant
support, encouragement and understanding during my studies.
vii
ABSTRACT
Injection molding is a manufacturing process for producing part for both thermoplastic and
thermosetting plastic material. Objective of this project to determine the parameter effect to
the warpage and shrinkage of the handphone casing and to determine the optimization
parameter for reduce the warpage and shrinkage. For this project 3D scanner are use to scan
the hand phone casing to get the parameter and analyse with MoldFlow simulation software
to optimize the effect to warpage and shrinkage. Shrinkage and warpage tendencies in
molded parts,are influenced by actions taken in each and all of the manufacturing stages of
part design, material selection, tool design, and processing. The mold temperature(MT),
packing time (Pt), packing pressure (PP) and cooling time (Ct) in the packing stage are
considered as machining parameters. As increase in mold temperature (MT), the shrinkage
also increase and as increase in cooling time (Ct), the shrinkage decrease. Other than that,
as increase the packing pressure (PP), the shrinkage usually decrease.
viii
ABSTRAK
Pembentukan suntikan adalah proses pembuatan untuk menghasilkan bahagian untuk
kedua-dua bahan plastik termoplastik dan termoset. Tujuan projek ini untuk mengetahui
pengaruh parameter pada melenting dan penyusutan selongsong telefon bimbit dan juga
untuk menentukan parameter yang optimum untuk mengurangkan melenting dan susut.
Dalam projek ini, 3D scanner yang digunakan untuk mengimbas solongsong telefon bimbit
untuk mendapatkan parameter dan dianalisis dengan perisian simulasi MoldFlow untuk
mengoptimumkan kesan untuk melenting dan susut. Susut dan kecenderungan melenting di
bahagian dibentuk, dipengaruhi oleh tindakan yang diambil dalam mana-mana dan semua
tahap pembuatan desain bahagian, pemilihan material, rekaan alat, dan pemprosesan. Suhu
acuan (MT), masa padatan (Pt), tekanan padatan (PP) dan masa pendinginan (Ct) dalam
tahap kemasan dianggap sebagai parameter pemesinan. Seperti kenaikan suhu acuan (MT),
susut juga meningkat dan peningkatan masa pendinginan (Ct), susut juga menurun. Selain
itu, seperti peningkatan tekanan padatan (PP), susut biasanya menurun.
x
TABLE OF CONTENTS
Page
TITLE i
APPROVAL DOCUMENT ii
SUPERVISOR’S DECLARATION iii
EXAMINER’S DECLARATION iv
STUDENT’S DECLARATION v
DEDICATION vi
ACKNOWLEDGEMENTS vii
ABSTRACT viii
ABSTRAK ix
TABLE OF CONTENTS x
LIST OF TABLE xiii
LIST OF FIGURE xiv
CHAPTER 1 INTRODUCTION
1.1 Project Background 1
1.2 Project Title 2
1.3 Objective 2
1.4 Problem Statements 2
1.5 Scope of Project 3
CHAPTER 2 LITERATURE REVIEW
2.1 Introduction 5
2.2 Injection Molding 6
2.3 Warpage 9
2.4 Shrinkage 10
2.5 Parameter 12
xi
2.5.1 Injection Time 14
2.5.2 Mold Temperature 14
2.5.3 Packing Time 14
2.5.4 Packing Pressure 15
2.5.5 Melt Temperature 15
2.5.6 Cooling Time 16
2.6 MoldFlow Simulation Software 16
2.7 SolidWorks 19
2.8 3D scanner 20
2.9 Conclusion 22
CHAPTER 3 METHODOLOGY
3.1 Introduction 24
3.2 Flow Chart 25
3.3 Decide Objective and Scope of Project 26
3.4 Literature 26
3.5 3D Modelling Of Hand Phone Casing Using 3D Scanners 27
3.6 Generation of Hand Phone Casing 34
3.7 Dimension Obtain For Solidwork 34
3.8 Analysis Using Moldflow Simulation Software 34
3.9 Generation of New Molding Parameter 35
3.10 Analysis 35
3.11 Documentation & Presentation 36
3.12 Conclusion 36
CHAPTER 4 RESULTS & DISCUSSION
4.1 Introduction 37
4.2 Material Selection 37
4.3 Result 39
4.3.1 Result for Top Hand Phone Casing 39
4.3.1.1 Mold Temperature 39
xii
4.3.1.2 Melt Temperature 41
4.3.1.3 Injection Pressure 43
4.3.1.4 Cooling Time 45
4.3.2 Result for Bottom Hand Phone Casing 47
4.3.2.1 Mold Temperature 47
4.3.2.2 Melt Temperature 49
4.3.2.3 Injection Pressure 51
4.3.2.4 Cooling Time 53
4.4 Discussion 55
4.4.1 Mold Temperature 55
4.4.2 Melt Temperature 55
4.4.3 Injection Pressure 55
4.4.4 Cooling Time 56
CHAPTER 5 CONCLUSIONS & RECOMMENDATION
5.1 Introduction 57
5.2 Conclusion 57
5.3 Recommendation 58
REFERENCES 61
xiii
LIST OF TABLES
Table No. Title Page
4.1 Properties to Analyze Mold Temperature Parameters 38
4.2 Properties to Analyze Melt Temperature Parameters 38
4.3 Properties to Analyze Injection Pressure Parameters 39
4.4 Properties to Analyze Cooling Time Parameters 39
4.5 Result Warpage and Shrinkage for Mold Temperature 41
4.6 Result Warpage and Shrinkage for Melt Temperature 42
4.7 Result Warpage and Shrinkage for Injection Pressure 44
4.8
4.9
4.10
4.11
4.12
Result Warpage and Shrinkage for Cooling Time
Result Warpage and Shrinkage for Mold Temperature
Result Warpage and Shrinkage for Melt Temperature
Result Warpage and Shrinkage for Injection Pressure
Result Warpage and Shrinkage for Cooling Time
46
48
50
52
54
xiv
LIST OF FIGURES
Figure No. Title Page
2.2.1 The injection major part 6
2.2.2 The injection molding major part (front view) 7
2.4.1 The pvT curves for amorphous and crystalline polymers 11
2.4.2 Processing and design parameters that affect part shrinkage 12
2.6.1 Example of warp analysis 16
2.6.2 Preview of moldflow Simulation Software 17
2.8.1 3D scanner 20
3.5.1
3.5.2
3.5.3
3.5.4
3.5.5
3.5.6
3.5.7
3.5.8
3.5.9
3.5.10
3.5.11
3.5.12
3.7.1
Image from 3d Scanner for Front Cover Top
Image from 3d Scanner for Front Cover Bottom
Image from 3d Scanner for Back Cover Top
Image from 3d Scanner for Back Cover Bottom
Image from 3d Scanner for Front Cover Top
Image from 3d Scanner for Front Cover Bottom
Image from 3d Scanner for Back Cover Top
Image from 3d Scanner for Back Cover bottom
Image from 3d Scanner for Front Cover after Merge
Image from 3d Scanner for Back Cover after Merge
Image from 3d Scanner for Back Cover after Edit
Image from 3d Scanner for Back Cover after Edit
Solidwork Drawing Bottom Hand Phone Casing
27
27
28
28
29
29
30
30
31
31
32
32
33
xv
3.7.2 Solidwork Drawing Top Hand Phone Casing 34
4.1.1 Warpage at Mold Temperature Is 60°C 40
4.1.2 Shrinkage at Mold Temperature Is 60°C 40
4.1.3 Warpage at Melt Temperature Is 205°C 41
4.1.4 Shrinkage at Melt Temperature Is 205°C 41
4.1.5 Warpage at Injection Pressure Is 120 MPa 43
4.1.6 Shrinkage at Injection Pressure Is 120 MPa 44
4.1.7
4.1.8
4.1.9
4.1.10
4.1.11
4.1.12
4.1.13
4.1.14
4.1.15
4.1.16
Warpage at Cooling Time is 20s
Shrinkage at Cooling Time is 20s
Warpage at Mold Temperature Is 60°C
Shrinkage at Mold Temperature Is 60°C
Warpage at Melt Temperature Is 205°C
Shrinkage at Melt Temperature Is 205°C
Warpage at Injection Pressure Is 120 MPa
Shrinkage at Injection Pressure Is 120 MPa
Warpage at Cooling Time is 20s
Shrinkage at Cooling Time is 20s
45
46
47
48
49
50
51
52
53
54
CHAPTER 1
INTRODUCTION
1.1 Project Background
Injection molding is a very mature technology, but the growth of layer-build,
additive, manufacturing technologies has the potential of expanding injection molding into
areas not commercially feasible with traditional molds and molding technique. What is
missing is the fundamental understanding of how the modifications to the mold material
and mold manufacturing process impact both the mold design and the injection molding
process. Plastic injection processes comprise plastication, injection, packing, cooling,
ejection and process/part quality control applications. These steps are followed for the
parts, which are designed to be produced by plastic injection method.
There are many factors affecting warpage and shrinkage. These are mold
temperature, melt temperature, packing pressure, packing time, cooling time, injection
velocity, injection time, injection pressure, gate location, runner type, etc. The warpage and
shrinkage is reduced further by optimizing the six significant process variables: injection
time, post fill (cooling plus packing) time, packing time, packing pressure, melt
temperature, and coolant temperature. Computer-aided analysis and engineering software
are used in order to minimum the warpage. For plastic injection process, one of the
commercial computer-aided engineering software is the MoldFlow. In this study,
MoldFlow simulation software is used to make the analysis and optimize the parameter
effect to the warpage and shrinkage.
2
1.2 Project Title
Optimization of Molding Parameter Effect to Warpage and shrinkage based on
Plastic Flow Simulation Software: Hand Phone Casing
1.3 Objective
1. To define the molding parameter in injection molding of hand phone casing.
2. To determine parameter effect in molding parameter to warpage and shrinkage of hand
phone casing.
3. To optimize the molding parameter and minimize the warpage and shrinkage of hand
phone casing based on Plastic Flow simulation software.
1.4 Problem Statements
In this project, warpage and shrinkage are depends on so many factors and one of it
is the injection molding parameter. The parameter includes mold temperature, melt
temperature, injection time, packing pressure, packing time, and so on. 4 parameters were
chosen to make the analysis in order to make the optimization of molding parameter and
minimize the warpage and shrinkage of hand phone casing. The parameters include mold
temperature, melt temperature, injection pressure and cooling time.
The parameters are used to make analysis base on plastic flow simulation software.
In this project, MoldFlow Plastic Insight was use to make the analysis on the chosen
parameter. The analysis includes warpage and shrinkage in hand phone casing to optimize
the parameters that affect the both defect.
3
1.5 Scope of Project
Obtain the data and all the information for the title to understand this project by do a
lot of research that come from many sources such as internet, books, journals, articles and
many more. In other to make more understand on this project, the guidance from the
supervisor is important. Also, to check the progress is going smoothly by make sure that the
data and information that obtain from the source are really useful for this project. Meeting
with supervisor is needed in every week until this project is done.
3D scanning is used in this project also referred as 3D digitizing. This device is
utilization of a three dimensional data acquisition device to acquire a multitude of X, Y, Z
coordinates on the surface of a physical object or object’s shape and appearance include
points. The scanner then uses these points to form a 3D digital model of the part. This
captured data is typically stored as a list of xyz-coordinates in a point cloud file. 3D
scanners can be categorized as contact (CMM arms) or non-contact (white light, 3D laser
scanners, or stereo-vision based). Some can even capture internal features.
After getting the shape of the object from the 3D scanning, then the data is
transferred into CAD software that known as SolidWorks. SolidWorks is software that uses
to utilize a parametric feature-based approach to create models and assemblies. Parameters
refer to constraints whose values determine the shape or geometry of the model or
assembly. The data is transferred into the SolidWorks because to get the parameters of the
objects that will use in further analysis.
Plastic Flow simulation software then will be used to make the analysis to the
parameter of the object. SolidWorks Flow Simulation is a Computational Fluid Dynamics
(CFD) product for SolidWorks users. It is embedded inside SolidWorks and can perform
fluid flow and heat transfer analysis for some types of fluids (liquids, gases, Non
Newtonian fluids, Compressible liquid. Other than that, it’s a sophisticated practice that’s
gaining popularity. It helps identify a variety of potential problems and improvements for a
4
mold before it gets built. With this software, analysis about this project can be done also get
result to optimize the molding parameter and reduce the warpage and shrinkage.
5
CHAPTER 2
LITERATURE REVIEW
2.1 Introductions
This project title is optimization of molding parameter effect to warpage and
shrinkage based on plastic flow simulation software. Optimization means to make
something as good as possible. In this case, optimization of molding parameter is to make
improvement about the molding parameter that effect to warpage and shrinkage in injection
molding.
Plastic injection processes comprise plastication, injection, packing, cooling,
ejection and process/part quality control applications. These steps are followed for the
parts, which are designed to be produced by plastic injection method. Having initial
knowledge about the process that will be undertaken is necessary because of present-day
competitive conditions that force us to produce faster and cheaper with a higher quality,
such as minimum warpage, sink marks, etc. Computer-aided analysis and engineering
software are used in order to meet this necessity.
In plastic injection process, there is one the commercial computer-aided engineering
software’s is the MoldFlow Plastic Insight. In this study, process parameters such as mold
temperature, melt temperature, packing pressure, packing time, cooling time, runner type
and gate location are considered as parameter variables in order to minimize the warpage
and shrinkage.
6
2.2 Injection Molding
Injection molding is one of the most common processing methods for
thermoplastics. Nowadays one sees a multitude of different types of injection molded
products in homes, vehicles, offices and factories. These include combs, syringes, paint
brush handles, crash helmets, telephones, soft drink glasses, gearwheels, brief cases,
television housings, typewriters—the list is almost endless.
In the injection molding process, a thermoplastic in the form of granules or powder,
passes from a feed hopper into a barrel where it is heated until it becomes soft. It is then
forced through a nozzle into a relatively cold mold which is clamped tightly closed. After
the plastic is cooled and solidified, the article is ejected and the cycle is repeated. The major
advantages of the process includes its versatility in molding a wide range of products, the
ease with which automation can be introduced, the possibility of high production rates and
the manufacture of articles with close tolerances (R.J. Crawford,1989).
Figure 2.21: The injection major part
Adapted from:
7
Figure 2.22: The injection molding major part (front view)
Adapted from:
Injection molding is one of the most important polymer processing methods for
producing plastic parts (H.T. Paro, C.P. Bosnyak, K. Sehanobish, 1986). Process
parameters in addition to molding material and part design are major factors affecting the
quality of plastic parts produced by injection molding. Quality of these parts is often
associated with warpage. Effects of process parameters on non-uniform shrinkage leading
to warpage are investigated from several aspects in literature (A.I. Isayav, Marcel Dekker,
1987).
The injection molding process was first designed in the 1930s and was originally
based on metal die casting designs. Injection molding offers many advantages to alternative
manufacturing methods, including minimal losses from scrap (since scrap pieces can be
melted and recycled), and minimal finishing requirements. Injection molding differs from
metal die casting in that molten metal’s can simply be poured; plastic resins must be
injected with force.
8
The process uses large injection molding machines, which advance the resins
through six major processes to produce everything. Although an injection molding machine
is a complex piece of equipment, it consists of two basic elements, the injection unit and
the clamping unit.
The process starts with a mold, which is clamped under pressure to accommodate
the injection and cooling process. Then, pelletized resins are fed into the machine, followed
by the appropriate colorants. The resins then fall into an injection barrel, where they are
heated to a melting point, and then injected into the mold through either a screw or
ramming device.
Then comes the dwelling phase, in which the molten plastics are contained within
the mold, and hydraulic or mechanical pressure is applied to make sure all of the cavities
within the mold are filled. The plastics are then allowed to cool within the mold, which is
then opened by separating the two halves of the mold. In the final step, the plastic part is
ejected from the mold with ejecting pins. The completed part may contain extraneous bits
called runners, which are trimmed off and recycled. The entire process is cyclical, with
cycle times ranging from between ten and 100 seconds, depending on the required cooling
time.
The injection molding process requires some complex calculations. Every different
type of resin has a shrinkage value that must be factored in, and the mold must compensate
for it. If this value is not precisely determined, the final product will be incorrectly sized or
may contain flaws. Typically, this is compensated for by first filling the mold with resin,
holding it under pressure, and then adding more resin to compensate for contraction. Other
complications may include burned parts resulting from the melt temperature being set too
high, warpage resulting from an uneven surface temperature, or incomplete filling due to a
too slow of an injection stroke.
9
2.3 Warpage
Warpage is a distortion where the surfaces of the molded part do not follow the
intended shape of the design. Part warpage results from molded-in residual stresses, which,
in turn, is caused by differential shrinkage of material in the molded part. If the shrinkage
throughout the part is uniform, the molding will not deform or warp, it simply becomes
smaller. However, achieving low and uniform shrinkage is a complicated task due to the
presence and interaction of many factors such as molecular and fiber orientations, mold
cooling, part and mold designs, and process conditions (Kurtaran, H. Kurtaran, B. Ozcelik,
T. Erzurumlu, 2005 ; Dong, B.B. Dong, C.Y. Shen, C.T. Liu, 2005).
.
Warpage in molded parts results from differential shrinkage. Variation in shrinkage
can be caused by molecular and fiber orientation, temperature variations within the molded
part, and by variable packing, such as over-packing at gates and under-packing at remote
locations, or different pressure levels as material solidifies across the part thickness.
Thicker part sections have limited cooling available and cool more slowly than their
thinner or better cooled counterparts. Ribs, bosses, corners, differential mold temperatures,
etc., all contribute to variations in cooling time and rate of cooling. In the mold, a part
develops a differential temperature profile. When the part is ejected, the thicker sections
are still cooling while thinner sections may have reached their final temperature. As the
part cools further the thicker areas, which are no longer restrained, contract and possibly
cause warpage.
10
Other causes:
• Warping can also be caused due to non-uniform mold temperatures or cooling rates.
• Non-uniform packing or pressure in the mold.
• Alignment of polymer molecules and fiber reinforcing strands during the mold fill
results in preferential properties in the part.
• Molding process conditions--too high an injection pressure or temperature or improper
temperature and cooling of the mold cavity.
2.4 Shrinkage
The shrinkage of molded plastic parts can be as much as 20 percent by volume,
when measured at the processing temperature and the ambient temperature. Crystalline and
semi-crystalline materials are particularly prone to thermal shrinkage; amorphous materials
tend to shrink less. When crystalline materials are cooled below their transition
temperature, the molecules arrange themselves in a more orderly way, forming crystallites.
On the other hand, the microstructure of amorphous materials does not change with the
phase change. This difference leads to crystalline and semi-crystalline materials having a
greater difference in specific volume ( ) between their melt phase and solid (crystalline)
phase. This is illustrated in Figure 2.41 below. Cooling rate also affects the fast-cooling
pvT behavior of crystalline and semi-crystalline materials (Kurtaran , H. Kurtaran, B.
Ozcelik, T. Erzurumlu, 2005; Dong, B.B. Dong, C.Y. Shen, C.T. Liu, 2005).
11
FIGURE 2.41: The pvT curves for amorphous and crystalline polymers and the specific
volume variation ( ) between the processing state (point A) and the state at room
temperature and atmospheric pressure (point B). Note that the specific volume decreases as
the pressure increases.
Adapted from:
Causes of excessive part shrinkage Excessive shrinkage, beyond the acceptable
level, can be caused by the following factors. The relationship of shrinkage to several
processing parameters and part thickness is schematically plotted in Figure 2.
• low injection pressure
• short pack-hold time or cooling time
• high melt temperature
• high mold temperature
• Low holding pressure.
Problems caused by part shrinkage Uncompensated volumetric contraction leads to
either sink marks or voids in the molding interior. Controlling part shrinkage is important in
part, mold, and process designs, particularly in applications requiring tight tolerances.
Shrinkage that leads to sink marks or voids can be reduced or eliminated by packing the
top related