IJRI-MT-01-005

1International Journal of Research and Innovation (IJRI)

PREDICTIVE ANSLYSIS OF GATE AND RUNNER SYSTEM FOR PLASTIC INJUCTION MOULD

Paravataneni Prabhu Kumar, D.Gopichand Mother Theresa Institute of Technology(mist) Sanketika Nagar Sathupally Khammam,India

*Corresponding Author: Paravataneni Prabhu Kumar, Mother Theresa Institute of Technology(mist) Sanketika Nagar Sathupally Khammam,India Published: Sep 30, 2014

Volume No: IIssue No. : III

Citation:V.Venkata Krishna Mohan, D.Gopichand (2014) PREDICTIVE ANSLYSIS OF GATE AND RUNNER SYSTEM FOR PLASTIC INJUCTION MOULD

INTRODUCTION TO INJECTION MOULDING

Injection molding machine

From Plastics Wiki, free encyclopedia

Injection molding machines consist of two basic parts, an injection unit and a clamping unit.Injection molding machines differ in both injection unit and clamping unit. The name of the injection molding machine is generally based on the type of injection unit used.

RUNNERS

Distribution system for the resin from the sprue to the cavities Flow characteristics (viscosity), temper-ature and other factors are important in determin-

ing the runner diameter and lengthIf the diameter of the runner is too small or the length is too long, the resin can freeze in the runner before the mold is completely fullIf the runner system is too large, excess material would be ejected and too much regrind createdIf the resins have a high viscosity, larger runners are needed compared to low viscosity resinThe optimum flow of the resin through the runner system depends on the shape and diameter of the channelRound channel give the best flow characteristics but difficult to machineMachining cost can be reduce by machining one side of the mold platesBetter shape where the depth of the channel is at least two-thirds the size of the width and the sides are tapered between 2 to 5.

Secondary Runners

Secondary runner channel are used for multi cav-ity molds The flow into the secondary channel should be streamlined (angle in flow direction)The streamlined minimizes shear on the resin

Runners are the major part of feed system of mould-ing process it has to design very carefully most com-monly USED CROSS-SECTIONS AS BELOW.

Abstract

A runner system is an assembly of heated components used in plastic injection molds that inject molten plastic into the cavities of the mold. Every injection mold design has to have a gate or an opening through which the molten plastic is injected into the cavity of the mold. The type and size of gate plays a very significant role in the process of injection molding and must not be overlooked. Gates vary in size and shape depending upon the type of plastic being molded and the size and shape of the part as well. Obviously, larger parts require larger gates, or even several gates. The aim of the project work is to specify optimum design of runner and gate systems to enhance the production rate for plastic part manufacturing. Literature study will be done on runner and gate system for understanding simulation approach. Data collection will be done to brief about runner and gate system importance, design method and variations. Plastic flow analysis will be done on digital prototype of a specimen by various runner and gate profiles and also done by changing materials. The optimum profiles for the runner and gate system by comparing flow results with specific materials with profiles.

Peer Review- 1401-1402

International Journal of Research and Innovation (IJRI)


The above image shows machine schematic


Gate type

As important as selecting the optimal gate size and location is the choice of the type of gate.Gate types can be divided between manu-ally and automatically trimmed gates.Manually trimmed gatesManually trimmed gates are those that re-quire an operator to separate parts from runnersduring a secondary operation. The reasons for using manually trimmed gates are:

The gate is too bulky to be sheared from the part as the tool is opened. Some shear-sensitive materials (e.g., PVC) should not be exposed to the high shearrates inherent to the design of automati-cally trimmed gates. Simultaneous flow distribution across a wide front to achieve specific orientation offibers of molecules often precludes auto-matic gate trimming

Gate types trimmed from the cavity manu-ally include: Sprue gate Edge gate Tab gate Overlap gate Fan gate Film gate Diaphragm gate External ring Spoke or multipoint gate

Sprue gate

Recommended for single cavity molds or for parts requiring symmetrical filling. This

type of gate is suitable for thick sections be-cause holding pressure is more effective. A short sprue is favored, enabling rapid mold filling and low-pressure losses. A cold slug well should be included opposite the gate. The disadvantage of using this type of gate is the gate mark left on the part surface af-ter the runner (or sprue) is trimmed off.

Freeze-off is controlled by the part thick-ness rather than determined the gate thick-ness. Typically, the part shrinkage near the sprue gate will be low; shrinkage in the sprue gate will be high. This results in high tensile stresses near the gate.DimensionsThe starting sprue diameter is controlled by the machine nozzle. The sprue diameter here must be about 0.5 mm larger than the nozzle exit diameter. Standard sprue bush-ings have a taper of 2.4 degrees, opening to-ward the part. Therefore, the sprue length will control the diameter of the gate where it meets the part; the diameter should be at least 1.5 mm larger than or approximately twice the thickness of the part at that point. The junction of sprue and part should be radiused to prevent stress cracking

A smaller taper angle (a minimum of one degree) risks not releasing the sprue fromthesprue bushing on ejection. A larger taper wastes material and ex-tends cooling time. Non-standard sprue tapers will be more expensive, with little gain.


Edge gate

The edge or side gate is suitable for medi-um and thick sections and can be used onmulticavity two plate tools. The gate is lo-cated on the parting line and the part fills from the side, top or bottom.

Dimensions

The typical gate size is 80% to 100% of the part thickness up to 3.5 mm and 1.0 to 12 mm wide. The gate land should be no more than 1.0 mm in length, with 0.5 mm being the optimum.

Tab gate

A tab gate is typically employed for flat and thin parts, to reduce the shear stress in the cavity. The high shear stress generated around the gate is confined to the auxiliary tab, which is trimmed off after molding. A tab gate is often used for molding P.

Dimensions

The minimum tab width is 6 mm. The min-imum tab thickness is 75% of the depth of the cavity.

Overlap gate

An overlap gate is similar to an edge gate, except the gate overlaps the wall or sur-faces. This type of gate is typically used to eliminate jetting.

DimensionsThe typical gate size is 10% to 80% of the part thickness and 1.0 to 12 mm wide. The gate land should be no more than 1.0 mm in length, with 0.5 mm being the optimum.

Fan gateA fan gate is a wide edge gate with variable thickness. This type is often used for thick-sectioned moldings and enables slow injec-tion without freeze-off, which is favored for low stress moldings or where warpage and dimensional stability are main concerns. The gate should taper in both width and thickness, to maintain a constant cross sectional area. This will ensure that:The melt velocity will be constant.The entire width is being used for the flow.The pressure is the same across the entire width.DimensionsAs with other manually trimmed gates, the maximum thickness should be no more than 80% of the part thickness. The gate width varies typically from 6 mm up to 25% of the cavity length.


External ring gate

This gate is used for cylindrical or round parts in a multicavitymould or when a dia-phragm gate is not practical. Material en-ters the external ring from one side form-ing a weld line on the opposite side of the runner this weld line is not typically trans-ferred to the part.DimensionsTypical gate thickness is 0.25 to 1.5 mm.

Film or flash gateA film or flash gate consists of a straight runner and a gate land across either the entire length or a portion of the cavity. It is used for long flat thin walled parts and provides even filling.Shrinkage will be more uniform which is important especially for fiber reinforcedthermoplastics and where warpage must be kept to a minimum.DimensionsThe gate size is small, typically 0.25mm to 0.5mm thick. The land area (gate length) must also be kept small, approximately 0.5 to 1.0 mm long.

Diaphragm gate

A diaphragm gate is often used for gating cylindrical or round parts that have an open inside diameter. It is used for single cavity molds that have a small to medium

internal diameter. It is used when concen-tricity is important and the presence of a weld line is not acceptable.DimensionsTypical gate thickness is 0.25 to 1.5 mm.

Spoke gate or multipoint gate

This kind of gate is used for cylindrical parts and offers easy de-gating and mate-rial savings.Disadvantages are the possibility of weld lines and the fact that perfect roundness is unlikely.DimensionsTypical gate size ranges from 0.8 to 5 mm diameter

Pin gates

Pin gates are only feasible with a 3-plate tool because it must be ejected separate-ly from the part in the opposite direction The gate must be weak enough to break off without damaging the part. This type of gate is most suitable for use with thin sections. The design is particularly useful when multiple gates per part are needed to assure symmetric filling or where long flowpaths must be reduced to assure packing to all areas of the part.DimensionsGate diameters for unreinforced thermo-plastics range from 0.8 up to 6 mm. Small-er gates may induce high shear and thus thermal degradation. Reinforced thermo-plastics require slightly larger gates > 1 mm The maximal land length should be 1 mm.


Advised gatedimensions can be found in the table below

Submarine (tunnel) gates

A submarine gate is used in two-plate mold construction. An angled, tapered tunnel ismachined from the end of the runner to the cavity, just below the parting line. As the parts and runners are ejected, the gate is sheared at the part. The tunnel can be lo-cated either in the moving mould half or in the fixed half. A sub-gate is often located into the side of an ejector pin on the non-visible side of the part when appearance is important. To degate, the tunnel requires a good taper and must be free to bend.DimensionsTypical gate sizes 0.8 mm to 1.5 mm, for glass reinforced materials sizes could be larger.

Most raw materials can be used. The resin is in pellets before processing. Acrylonitrile-Butadiene-Styrene ABSNylon PAPolycarbonate PCPolypropylene PPPolystyrene GPPS INTRODUCTION TO CAD

Computer Aided Design (CAD) is a tech-nique in which man and machine are blended in to problem solving team, inti-mately coupling the best characteristics of each. The result of this combination works better than either man or machine would work alone , and by using a multi disci-pline approach, it offers the advantages of integrated team work.

The above image shows semi circular runner

Modeling of SpecimanModel of Speciman With Runners


The above image shows square runner

The above image shows trapezoid

The above image shows modified trapezoid


2D DRAFTING


MOULD FLOW ANALYSIS

Mould flow, 3D solids-based plastics flow simula-tion that allows plastics part designers to determine the manufacturability of their parts during the pre-liminary design stages and avoid potential down-stream problems, which can lead to delays and cost overruns. Following are the benefits: Optimize the part wall thickness to achieve uniform filling patterns, minimum cycle time and lowest part cost Identify and eliminate cosmetic is-sues such as sink marks, weld lines and air traps. Determine the best injection locations for a given part design Mould flow analysis gives you the ability to main-

tain the integrity of your product designs. It pro-vides you the tools to quickly optimize part designs and check the impact of critical design decisions on the manufacturability and quality of the product early in the design process.There is no need to: Compromise the aesthetics of your design concept for manufacturability; Go through a lengthy trial and error process to find the most suitable material to produce the part with the highest possible quality and the lowest possible cost Find out during trial runs that the produced part has visual blemishes, such as sink marks, weld lines, air traps or burn marks

MATERIAL PROPERTIES

Acrylonitrile Butadiene System (ABS)

High Density Polyethylene (HDPE)

10


Polyvinyl Chloride (PVC)

Plastic Flow Analysis of Specimen Using Semi Circular Runner

The above image shows solid model

11


The above image shows fill time

The above image shows confidence of fill

The above image shows injection pressure

12


The above image shows pressure drop

The above image shows flow front temp

The above image shows quality prediction

13


The above image shows weld lines

The above image shows air traps

The above image shows next best gate location

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The above image shows cooling quality

The above image shows surface temp variance

The above image shows freeze time variance

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The above image shows skin orientation

Plastic Flow Analysis Of Specimen Using Square Runner


The above image shows Injection Pressure

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The above image shows surface temp variancePlastic Flow Analysis of Specimen Using Trapezoid Runner



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Plastic Flow Analysis of Specimen Using Modified Trapezoid Runner



Model of Modified Trapezoid Runner With Gates Geomentry

The above image shows semi circular gate

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The above image shows square type gate

The above image shows modified trapezoid type gate

2D DRAFTING

19


The above images shows 2d drafting

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Plastic Flow analysis of Specimen using Semi - Circular Gate



Plastic Flow Analysis of Specimen Using Square Gate


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Plastic Flow Analysis of Specimen Using Trapezoid Gate



22


Plastic Flow of Specimen Using Modified Trapezoid Gate



Model of Modified Trapoizoid Runner with Types of Gates Systems

The above image shows overlap type gate

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The above image shows bottom type gate

The above image shows top type gate

The above image shows tap type gate

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The above image shows fan type gate

The above image shows ring type gatePlastic Flow analysis of Specimen using modified trapezoid runner with over

Lap Gate


25



Plastic Flow analysis of Specimen using modified trapezoid runner with Bottom Gate



26


Plastic Flow analysis of Specimen using modified trapezoid runner with Top Gate


The above image shows fill timePlastic Flow analysis of Specimen using modified trapezoid runner with Tap Gate


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Plastic Flow analysis of Specimen using modified trapezoid runner with Fan Gate



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Plastic Flow analysis of Specimen using modified trapezoid runner with Ring Gate



MODEL OF MULTI CAVITY SPECIMEN

Plastic Flow Analysis Using Multi Cavity System Polypropylene (PP)

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The above image shows confidence of fill

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The above image shows injection pressure

The above image shows pressure drop

The above image shows flow front temp

31


Results tables

The above image shows quality prediction

Semi-Circular Square Trapezoid Modified Trap-ezoid

Fill Time 6.82 5.12 5.34 5.27Injection Pres-sure

14.45 5.92 7.24 5.90

Pressure Drop 14.45 5.92 7.24 5.90Flow Front Temp 240.10 240.02 240.02 240.01Surface Temp Variance

91.58 89.18 101.80 39.99

Runner system

Gate geometryGate geometrySemi-Circular Square Trapezoid Modified Trap-

ezoidFill Time 5.34 5.56 5.77 5.11Injection Pres-sure

6.55 7.82 7.44 6.12

Pressure Drop 6.55 7.81 7.44 6.04Flow Front Temp 240 240.03 240.02 240Surface Temp Variance

1.46 1.67 1.69 1.61

Gate systems

Over Lap Bottom Top Tap Fan RingFill Time 4.93 5.58 5.21 6.02 5.34 3.37Injection Pressure

4.05 8.11 5.97 10.12 7.34 8.75

Pressure Drop

4.05 8.11 5.97 10.12 7.34 8.75

Flow Front Temp

240 240.01 240 240.02 240.01 240.02

Surface Temp Vari-ance

1.99 1.87 1.60 3.84 1.45 4.68

32


Multi cavity

PP ABS HDPE PVCFill Time 6.03 7.84 6.40 13.82Injection Pressure 18.77 28.38 34.87 43.87Pressure Drop 18.77 28.38 34.87 43.87Flow Front Temp 240.08 230.16 210.46 170.45Surface Temp Vari-ance

11.30 11.30 11.30 11.30

CONCLUSIONThis research paper gives the complete orientation on runner and gate system of plastic manufactur-ingMould.Initially literature survey and data collection was done on gate and runner system to understand the methodology and selection of geometryMould flow analysis was done using plastic advisor on various runners and gate profiles, to specify the optimum model for gate and runner.In first case:- Semi circular, square, trapezoid and modified trapezoid models where analyzed using standard pressure with regular material polypropyl-ene, In this case modified trapezoid runner system is giving optimum Flow with low pressure.In second case:- Various geometric profiles of gate system are implemented to provide the optimum gate geometry.In this case modified trapezoid gate geometry with modified trapezoid runner is having optimum qual-ity.In third case:-Different methods of gate systems are implemented to fine optimum feed system. In this case overlap type is showing good charter sticks.In fourth case:-The mould flow analysis was done using different materials on multi cavity model. In this case all the thermo plastics (PP, ABS, HDPE) is showing good charter sticks, along with trapezoid gate with runner with overlap system , but when coming to thermo setting plastic(PVC) is not suit-able for multicavity system.As per the obtaining results of above four differ-ent cases this research work concludes that modi-fied trapezoid runner and gate system with overlap method will perform better injection moulding pro-cess, it uses very low pressure, it losses pressure drop with nominal surface temperature variance.

REFERENCE1 Chandan Deep SinghDepartment of Mechanical Engineering,University College of Engineering, Punjabi Univer-sity, Patiala, (PB) (India2Mohd. RizwanHamsin, AzuddinMamat and Aznija-rAhmad-YazidDepartment of Engineering Design and Manufac-tureFaculty of Engineering, University of Malaya,3E. Bociga, T. Jaruga*Institute of Polymer Processing and Production Management,4E. Bociga, T. Jaruga*

Institute of Polymer Processing and Production Management,Czestochowa University of Technology,5Yuan Hsu1, Mark R. Jolly2and John Campbell21 Department of Materials Science and Engineering, National United University,6ThiTruc-Ngan Huynh*Department of Mechanical Engineering,National Kaohsiung University of Applied Sciences Kaohsiung, Taiwan, R.O.C.7Srisit Chianrabutra1, a, Anchana Wongsto2, b, Taweedej Sirithanapipat1, 2, cResearch and Development Institute of Industrial Production Technology (RDiPT)1Department of Mechanical Engineering2Faculty of Engineering, Kasetsart University,8SahajanandKamble1, Prof. Girish V A2, Mr. Shrid-har Bagalkot3 1Department of mechanical engineer-ing R.V. college of Engineering, Bangalore,560059 India E-mail 9Vikas B J 1, Chandra Kumar R 21M. Tech. Student, 2Asst. Professor, Department of Mechanical Engineering, R V College of Engineering, Karnataka,

Authors

Paravataneni Prabhu KumarExperience 3 yr in teaching

D.GopichandQualification: m.techDesignation: assistant profressorExperience :4 yr in teaching & 2 yr experience inInfoTech as design engineer

Abstract

IJRI-MT-01-005

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