1. 1
Project On
Quality Improvement of Plastic Injection Mould Design
using Mould Flow Analysis
Submitted in partial fulfillment of the requirements for the award of the degree
BACHELOR OF TECHNOLOGY
IN
MECHANICAL ENGINEERING
Submitted by
Jatinder Singh (0816232)
Bhupender Sharma (0816233)
Under the guidance of
Sh. PUNEET KATYAL
Assistant Professor
DEPARTMENT OF MECHANICAL ENGINEERING
GURU JAMBHESHWAR UNIVERSITY OF SCIENCE & TECHNOLOGY
HISAR
(May, 2012)
2. 2
CONTENTS
Title Page No.
Certificate i
Candidate’s Declaration ii
Acknowledgement iii
Abstract iv
List of figures v
CHAPTER-1
Introduction 1
Introduction to Plastics 2
Injection Mould Design 3
Polymer Selection 5
Types of Gates 8
Feed System 10
Ejection System 13
Cooling System 12
Mould Design & their Considerations 14
CHAPTER-2
Product Drawings 17
CHAPTER-3
Analysis Report 20
CHAPTER-4
Conclusion 27
REFERENCES 28
3. 3
ABSTRACT
The main objective of the project is to improve the Quality of Plastic Injection Mould Design using Mould
Flow Process. In this project, an attempt has been made to design & development of the automatic
injection molded product for “GLASS”. The work started with concept generation of a mould glass using
brainstorming approach. Design concepts were developed on CATIA and best design was selected based
on analysis results achieved on Plastic Advisor/Pro-E. The results revealed the quality of mould design. In
doing so, Concurrent Engineering and Computer Aided Engineering made Mould Design process quick
and simpler. The main consideration of this project work is the product & mould design of the existing
product and do its quality improvement using mould flow analysis.
4. 4
INTRODUCTION
A tool is required for converting plastic into a product. The tool is called to be mould. In our life
we need so many types of components to fulfill our requirements. All these components cannot
be made in single method and from a single material. So depending upon the components shape
and material used for manufacture we need different types of moulds. For larger production,
automatic moulds are used where as a hand mould uses where the cost rate is primarily
considered and produced them is given least importance. Automatic injection moulds are
generally used for small to large components with any complicated shapes. Keeping the above
things is mould this project report covers theoretical input into of plastic property, processing
techniques and tooling considerations.
5. 5
INTRODUCTION TO PLASTICS
PLASTICS:
A polymer which is shaped into a hard and tough utility article by the application of heat and
pressure by using suitable techniques. All plastics are polymer but all polymers are not plastics.
Plastics are classified in to two types:
Thermoplastics
Thermosets
Thermoplastics:
The material, which can be soften when heated and solidify on cooling, is known as
“thermoplastic”. These materials can be recycled and can be processed through injection
molding process, extrusion process, Blow Molding etc.
Ex: - PP, ABS, PE etc.
Thermosets:
It is the hardest form of plastics which cannot be reduced once processed. These materials are
processed through compression molding.
Ex:- UF, MF, Epoxy resin etc.
According to source point of view:
Natural Plastics : which are readily available in nature
Synthetic : Which do not occur in nature but have prepared artificially.
Application : plastic industry is passing through different phases
1st
Phase : Replacement of Non- Metallic material by simple plastic
2nd
Phase : Number of engineering and high performance plastics have been
Introduced which are capable of exhibiting higher performance
characteristics
3rd
Phase : Substitution of metallic parts by use of advanced fiber
Composites using carbon or other high performance fiber
Reinforced which need not be the final stage.
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INJECTION MOULD DESIGN
Injection molding is one of the most versatile processing methods by means for manufacturing
small clips to large industrial crates.
In mold design, there are some rules which must be paid attention. The rules are:
(1) Use uniform wall thicknesses throughout the part. This will minimize sinking, warping,
residual stresses, and improve mold fill and cycle times.
(2) Use generous radius at all corners. The inside corner radius should be a minimum of one
material thickness.
(3) Use the least thickness compliant with the process, material, or product design requirements.
Using the least wall thickness for the process ensures rapid cooling, short cycle times, and
minimum shot weight. All these result in the least possible part cost.
(4) Design parts to facilitate easy withdrawal from the mold by providing draft (taper) in the
direction of mold opening or closing.
(5) Use ribs or gussets to improve part stiffness in bending. This avoids the use of thick section
to achieve the same, thereby saving on part weight, material costs, and cycle time costs.
Concerning radius, Sharp corners greatly increase the stress concentration. This high amount of
stress concentration can often lead to failure of plastic parts.
In these operation plastics granules are feed into the cylinder through a hopper, where it is
plasticized and then forced out to other end of cylinder through a nozzle in to a relatively cool
mould held closed under pressure. Here melt cools and hardened until fully setup and then opens
and the molded part is removed.
Classification of injection mould based on the design feature and manner of operation:
The type of gating and means of de- gating
The type of ejection.
The presence or absence of external and internal undercuts on the products.
The manner in which the product is released from the mould.
Types of injection moulds:
Two plate mould
Three plate mould
Split mould
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Mould for threaded components
Hot runner moulds
Two plate mould:
The basic mould consists of two parts namely a fixed half and a moving half. When these two
parts are opened the molding can be extracted. Such an assembly is some times referred to, as a
single day light mould because when the mould is open there is only one space as it is normally
termed day light, between the two mould halves.
Advantages:
Large components can be molded easily
Economical
Simple mould construction
Disadvantages:
Manual attention is needed
Automatic degrading is not possible
Number of impression is limited.
Three plate mould:
When the mould is opened there are two day- lights. This design permits a particular feed
technique known as underfeeding and double day light is necessary in this case to permit the feed
sustem to floating cavity plate.
Advantages:
Small components with inner cross section can be molded easily
Less manual attention
Automatic degating is possible
Number of impressions can be mote when compared to two- plate mould.
Disadvantages:
Cost of mould construction is more
Split mould:
A mould which has a recess or projection is termed as undercut molding. The design for this type
of component is initially more complex than for the inline of draw component as it necessitates
the removal of that part of the impression which forms the conduct prior to rejection. For such
molded parts with undercuts i.e. articles that cannot be released in the direction of the mould
opening, requires moulds with more than one opening for such articles. Various methods have
8. 8
been developed that may be operated Manually, Mechanically, Hydraulically, Pneumatically or
electromechanical.
9. 9
POLYMER SELECTION
In choosing the “right material to do a job, we may find several products that will meet the
requirement but in any case they present a choice. One should first list the condition then list all
of materials that provide need to meet criteria.
Material selected:
As our component is “Glass” right material will be “PP” (Poly Propylene)
About the material:
PP is a soft thermoplastic co-polymer
Amorphous in nature
Manufacture:
Styrene and acrylonitrile monomers are added to polybutadiene latex and the mixture is warmed
to 50 c to allow absorption of monomers
A water soluble initiator such as potassiumper sulphate is the added to polymerize styrene and
acrylonitrile.
Characteristics:
Good tensile strength
High glass transition temperature
High melting point
Excellent chemical resistance
Very good fatigue resistance
Less tendency to Stress
Low ultraviolet resistance
Properties Value
Specific gravity (density) 0.903 g/cc
Tensile strength, Mpa 35.5
Elongation at break % 35
Hardness R100
10. 10
Melting Point (celcius) 164
Impact-strength, izod, J/M 134-120
Glass transition temperature 5
Mould shrinkage,% 1 – 2.5
Processed by:
Injection molding
Extrusion molding
Rotational molding
Blow molding
Application:
Automotive – Bumpers, Steering cover, Seat covers, Door covers, Acceleration pedal etc.
Electrical & Electronics – Radio, Transformer housing, Switch gears, Table & Wire
coating etc.
House Hold – Hair dryers, Microwave ovens trays, Glasses, Chairs etc.
Packaging – Packing of goods, contact lens cases, buttons etc.
Appliances – Drain tables, Door Handles etc.
Medical – Disposable syringes.
Other application - Ropes.
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TYPES OF GATES
1. Sprues:
Sprues are generally used when the parts have relatively thick walls or when highly viscous
melts require gentle processing. The spme has to be removed mechanically from the molded part
after ejection. Appropriate spme bushes are available as standard units in various versions, for
example, with twist locks, temperature control, etc., see also IS0 10072. Due to their large flow
diameters, conventional spmes exhibit minimal pressure loss. However, it must be taken into
consideration that a too-large spme can determine the cycle time. Thus maximum diameter ought
not to exceed part wall-thickness plus approx. 1.5 mm. If temperature-controlled (cooled) spme
bushes are used, this value may be exceeded. Conventional spmes offer optimum holding time in
the injection molding process. To prevent sink marks or non-uniform gloss, sufficient (separate)
cooling power should be provided at a distance from the gate.
Fig: 1.1
2. Pinpoint gate
In contrast to the spme, the pinpoint gate is generally separated from the molded part
automatically. If gate vestige presents a problem, the gate dl can be located in a lens-shaped
depression on the surface of the molded part. Commercially available pneumatic nozzles are also
used for automatic ejection of a runner with pinpoint gate. Pinpoint gating has been especially
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successful in applications for small and/or thin-walled molded parts. At separation, however,
drool has been a problem with certain polymers and premature solidification of the pin gate may
make it diffcult to optimize holding time.
Fig: 1.2
3. Diaphragm gate
The diaphragm is useful for producing, for instance, bearing bushings with the highest possible
degree of concentricity and avoidance of weld lines. Having to remove the gate by means of
subsequent machining is a disadvantage, as is one-sided support for the core. The diaphragm,
Fig. 1.3, encourages jetting which, however, can be controlled by varying the injection rate so as
to create a swelling material flow. Weld lines can be avoided with this type of gating.
Fig: 1.3
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FEED SYSTEM
Design of runner:
Shape of the cross section of the runner.
This is simple two-plate mold, having flat paring surface so we use the fully round runner.
A circular cross section provides the largest flow area for the less mass. On the other hand, it is
more expensive to produce because the runner must be cut in to two parts. Hence machining is
more expensive.
Runner efficiency =cross-section area/Periphery of the runner = 0.25D
(Higher the value, grater the efficiency)
Fig: 1.4
Runner Size:
When deciding the size if the runner the designer must consider the following factors:
The wall section and volume of the molding.
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The distance of impression from the main runner or sprue.
Runner cooling consideration.
The range of mould maker’s cutter available.
The plastics material to be used
D= (√W * 4√L)/3.7
Where
D= runner diameter (mm)
W= weight of molding (mm)
L= length of runner (mm)
Design of Gate:
Agate is a channel or orifice connecting the runner with the impression. It is the thinnest part of a
feed system.
The optimum size of a gate will depends upon a number of factors including:
The flow characteristics of the plastics material.
The wall section of the molding.
The volume or weight of the molding.
The molding temperature.
The mould temperature.
Positioning of gate:
The position of gate should be such that there is an even flow of melt in all the impression so that
it fills all the impression uniformly at the same time.
Selection of gate:
A channel or orifice connecting the runner to impression is called as the gate .it is one of the
thinnest parts of feed system.
Types of gate:
For two plate mould:
1. Direct sprue gate
2. Edge gate
3. Fan gate
For three plate mould:
1. Pinpoint gate
2. Subsurface gate
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3. Submarine gate
Gate used for our Glass model is Sprue Gate.
Sprue Gate:
Fig: 1.5
This type is particularly desirable for use with material give differential shrinkage characteristics
and it often used as an alternatively to film gating. This type of gate often used for multi-point
feeding and for single off centre feeding.
To prevent gate fracturing the area of molding adjacent to the gate particularly with more brittle
materials, it is desirable to taper the gate so that the gate is caused to break at the junction with
the secondary sprue.
Land length L= 0.75-1 mm suitable
Gate diameter d= nC4√A
Where n= material constant in mm.
A= surface area of the cavity (mm^2)
C= function of wall section thickness (t)
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EJECTION SYSTEM
Ejection Used For Glass Model:
All the thermoplastics material contracts as they solidify, which means that the molding will
shrink on to the core, which forms it. This shrinkage makes the molding difficult to remove.
So, it is advisable, it possible, to use a type of ejection mechanism which doesn’t have any marks
on the molded part.
Various types of ejection are there but for this component (Glass Model) pin ejection is used.
Pin Ejection:
In this system molding is ejected by the application of a force by a circular steel rod called an
ejector pin.
The ejector pin is headed to facilitate its attachments to the ejector plate assembly. When
actuator of machine actuates the ejector rod which is attached with the ejector plate assembly the
molding is ejected with the help of pin.
Different shapes of ejector pin may be used based on the size and shape of the molding i.e. D-
shaped pin, part pin, circular pin etc.
Fig: 1.6
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COOLING SYSTEM
All the injection moulds are generally provided with cooling in order to solidify the hot plastics
material, which is injected inside the cavity during molding process. Cooling is accomplished by
a continuous circulation of chilled water, hot oil flowing through the channel which is drilled
into various portion of the molding order to control the mould temperature depends upon the
types of plastics material to be used. For many commodity plastics cooling water supply is in the
order of 4-60~c at pressure of at 4-5 kg/cm^2.
Cooling used for Glass Model:
Rectangular circuit:
In this system we have to drill two flow ways on either side of the cavity and further drill is done
in other two sides to ensure that the flow ways are closed to all four ways of the cavity allowing
a more even temperature control.
It is rectangular in shape so it is called as rectangular circuit cooling.
Straight hole drilled channel:
This type of cooling is achieved by drilling straight holes. The two ends of the holes are
connected by hose nipple. On one end water is inset and by the other end the water is out let.
According to the size of the pate the number of drilled holes would be provided.
Fig: 1.7
18. 18
MOULD DESIGN & THEIR CONSICERATION
The following design concepts are followed while designing plastics products:
Parting line
Bosses
Ribs
Radii, filets, gussets
Draft angle
Parting line:
The parting line may be described as those lines made by the juncture of male and female mould
half and loose mould section. It should be around the section of the part having the large cross
section area.
Bosses:
Bosses are defined as protruding studs on a part that assist in the assembly of the plastics part
with the other piece. Special attention should be paid to the design of bosses in contact with
exterior surfaces avoid any heavy sections to prevent voids or external sink marks.
Ribs:
Ribs may be defined as long protrusions on the part which may be used to decorate or strengthen
the part of if properly placed to help prevent it from warp age, radii, fillets, gussets:
Fillets and radii are used at the ribs or bosses to facilitate the flow of plastics material and to
eliminate sharp corners thus reducing stress concentration in the molded article. The overall
advantages of fillets and radii are:
Eliminates cracking and increase impact strength
Reduce cycle time
Uniform density of the molded parts
Draft angle:
Article produced by the molding processors must have or draft on all surface perpendicular to the
parting lines of the mould. Plastics materials tend to shrink around cores. In order to remove the
mould parts, adequate taper must be provided.
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MOLD MATERIAL & THEIR APPLICATION
SL NO. ISI BS APPLICATION
01 T35CrMo1 V30 BH 11 Cavities, core, ejector pins, guides wear pads of
molds.
02 T35CrMo1 W1 V30 BH 11 Die casting dies & plastic molds.
03 40N112CrMo28 EN 24 Cavities, core ejector pins guides, wear pads for
moulds
04 T35Cr5Mo1 V1 - High tensile load applications, Max strength
05 13Ni3Cr80 - Cavity & Core
*06 T10 5Cr1 EN31 Used for guide pillars
**07 T103 BW 18 Used as wear plate, backing plate
***08 C10 & C14 EN 2A Bolster, support, block, plates, backing plates,
holder plate
09 C35Mn75 EN 8 Moulds with shorter run and owes non accurate
cavities
10 40Cr1 EN 18 Pillar, brush, sprue brush, locating ring, bigger
diameter ejector pins
11 50Cr1 V23 EN 47 Bright steel, used for ejector pins
12 T55Ni2Cr65Mo30 - Core, Cavity
* Bearing Steel
** Carbon Tool Steel
*** Mild Steel
(A) 1% Chromium Steel
23. 23
ANALYSIS REPORT
MOLDFLOW PLASTICS ADVISERS REPORT
Prepared By:
Prepared for:
Date: 01/May/2012
INTRODUCTION
SUMMARY
Release Level: 7.0
Glass
Part Name: Glass
Part Revision: 4
Material Supplier: Generic Default
Material Grade: Generic PP
Max Injection Pressure: 180.00 MPa
Mold Temperature: 40.00 deg.C
Melt Temperature: 240.00 deg.C
Model Suitability: Part model was highly suitable for analysis.
24. 24
Filling Analysis Glass
Moldability:
Your part can be easily filled but part quality may be
unacceptable.
View the Quality plot and use the Dynamic Adviser to
get help on how to improve the quality of the part.
Confidence: Medium
Injection Time: 0.67 sec
Injection Pressure: 47.64 MPa
Weld Lines: Yes
Air Traps: Yes
Shot Volume : 24.21 cu.cm
Filling Clamp Force: 23.94 tonne
Packing Clamp Force
Estimate @20%:
( 9.53 )MPa 13.12 tonne
Packing Clamp Force
Estimate @80%:
( 38.11 )MPa 52.48 tonne
Packing Clamp Force
Estimate @120%:
( 57.17 )MPa 78.72 tonne
Clamp Force Area: 135.03 sq.cm
Cycle Time: 7.91 sec
30. 30
CONCLUSION
The result of this study using 3D design tools in conjunction with Mold-Flow analysis produced
an accurate representation of plastic part.
In summary, the results of this paper have shown the following
• Cycle time is the most critical factor affecting quality control.
• There are three contributors of warpage, the shrinkage due to differential cooling shrinkage,
differential shrinkage and orientation shrinkage. In most cases, the differential cooling shrinkage
and differential shrinkage cannot be avoided.
It has been shown in this study that the Mold-Flow analysis can have a significant positive
impact in the design and manufacturing processes. The using of Mold-Flow could help shorten
development time.
31. 31
REFERENCES
1. American Foundrymen’s Society, 2000, “Basic Principles of Gating”, American
Foundrymen’s Society, Inc., Illinois.
2. American Foundry Society, 2001, “Aluminum Permanent Mold Handbook”, American
Foundry Society, Illinois.
3. Strong, A. Brent, 2000, “Plastics Materials and Processing”, 2nd ed., Prentice Hall, New
Jersey.
4. Thomas, B.G., 2002, “Casting Process Simulation and Visualization: A JOM-e Perspective”,
