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1、Injection Mold DesignADS Design TrainingPacificNovember,2003,Draft#2 03/11/2003,injection Mold design,GOODPART,Two-Plate Tool,Two-plate tool exploded view:Sprue bushingTop clamping plateA plateParting lineB plateSupport plateEjector retainer plateEjector plateEjector housing,1,2,3,4,Two-Plate Tool,O
2、peration sequence for 2-Plate tool design:,Three-Plate Tool,Three-plate tool exploded view:Sprue bushingTop clamping plateA plateParting lineX plateParting lineSupport plateB plateEjector retainer plateEjector plateEjector housing,1,2,3,4,5,Three-Plate Tool,Operation sequence for 3-Plate tool design
3、:,Sprue Bushing,Nozzle,Radius,Sprues Bushings,Helical Heater,Thermal Shut-Off,Heated Sprues,Cold Sprue,Heater Band,Gas Pipes,Sprues Bushings,Different heating methods for sprue bushings:,Sprues Pullers,Different methods for removing the sprue,Restricts flow path not recommended,Preferred,Sprues Pull
4、ers,Sucker pin designs,Material flows only through the molten portion of runner,Outer layer of material chills on contact with steel surface,Runners Flow,The outer layer of material in runners chills and freezes immediately(un-heated runners)Hence the actual flow is less than the runner cross sectio
5、n,A small increase in radius dramatically increases the flow through the runner.,R=Radius,Q=Volumetric Flow Rate,Q=,8n L,Q Proportional to R2,n R P,2,Runners Design,Flow rate through a runner,Full Round Most efficient,TrapezoidalAcceptable,Half RoundNot good,PL,Runners Design,Runner design recommend
6、ed profiles,RD,RD,RD W D3.24.83.24.86.44.86.48.06.48.011.08.09.512.79.5,Equivalent Round Runner,Design Alternative,Runners Design,Runner design trapezoidal profiles,W,D,W,Runners Design,Runner sizing recommendations:Balanced layout preferredPrimary runners:Full Round or Trapezoidal Length 250mm or l
7、onger:9.5mm diameter Length 75mm to 250mm:7.9mm diameter Length under 75mm:6.5mm diameterSecondary runners:6.5mm diameter minimum,Flow Direction,Cold SlugWell,Round Cross Section(3/16“to 3/8“Dia.)Short LengthCold Slug Wells,Cold SlugWell,Runners Design,Runners Design,Unbalanced runner layoutPressure
8、s will differ at gatesParts will have different packing pressure available,9.5mmPrimary,6.5mm,6.5mm,6.5mm,6.5mm,6.5mm,6.5mm,6.5mm,6.5mm,Runners Design,Artificially balanced runner layout difficult to tuneSecondary runner diameters altered to achieve same pressure at each gate,9.5mmPrimaryRunner,9.5m
9、m,6.5mm,6.5mm,9.5mm,9.5mm,6.5mm,6.5mm,9.5mm,Runners Design,Balanced runner layouts,Runners Design,8-cavity tool with balanced runner system,A Hot Runner System,Hot Runner Benefits Faster Cycles-15-20%Faster Eliminates Material Waste-No Sprues or Runners Improves Part Quality-Less Stress-Better Appea
10、rance,Differences in Design Philosophy,Good Heat InsulationOpen Unrestricted FlowLower Melt Inventory,HOT RUNNER SYSTEMSEXTERNALLY vs.INTERNALLY HEATED,Heating the Manifold,Smaller,Larger,Faster Colour ChangeShorter Residence Time,Lower ShearLower Pressure Drop,Melt Channel Sizing,Melt Passages Shou
11、ld be Externally Heated with four heaters.,Melt Channel Diameter should be 0.500”or larger.,Heater Watt Density should be 50 Watts/in3 Minimum.,Melt Channels should be polished and free of burs and dead spots,Manifold should be Naturally Balanced.,Manifold Recommendations,“L”,Locating Ring(not Inclu
12、ded),Standard“L”Sizesare 80,100,120 mm(3.15”,3.94”,4.72”),RadiusOptional,HOT SPRUE,THERMAL SHUTOFFTS SERIES,VALVE GATE,Extrusion,Gate,Melt Channel,Valve Stem,Heater,NozzleTip,InsulatingBubble,OPEN,CLOSED,Valve Gate,Compression Seal,PlugMoldmakersChoice,Diameter FitSeal,Cavity Plate=500,Manifold=5000
13、,Thermal Expansion of Steel.00000633 Per Inch Per Degree,6 in.=.017 In.12 in.=.034 In.18 in.=.051 In.,Direct Sprue GateEdge GateFan GateTunnel GateSingle,MultipleTab GatesDisk GateRing Gate,Flash GateDiaphragm GateModified“S”GatePin GateJump GateValve Gate Etc.,Types of Gating,Gate Design,Where?Thic
14、kest section;close to radii;away from high stress areas;centre of mass(not centre of part)How many?Depends on wall thickness and function(aesthetics);type of material;number of cavitiesWhat kind?Hot runner;hot tip;valve gate;three plate;edge gate;cashew gate;diaphragm gate;tunnel gate;flash gate;fan
15、 gate;direct sprue,Direct Sprue Gate,Molded Part,Sprue,Gate Design,Part,Runner,Gate,Land,Gate Design,Fan gate layout:,Top view,Side view,Top view,Gate Design,Fan gate layout:,Side view,Process Selection-Compression,Edge Gate,Single Tab Gate,Multiple Tab Gate,Gate,Tab,Sprue,6 in.Max,12 in.Max,Tab,Spr
16、ue,Gate,Gate,Tab,Multiple Tab Gate,Disk or Diaphragm Gate,Runner,Part,Runner,Sprue,Gate,Part,Runner Disk,Gate,Ring Gate,Runner,Parallel Runner,Gate,Flash Gate,Parallel Runner,0.020 Land Length,0.050,900,Pin Point Gating,Molded Part,Sprue,Parting Line,Tunnel,Gate(into side of ejector pin),Zero Land L
17、ength,Ejector pin(fasten head to prevent pin turning),Grind Flat on Gate Side,Min.20,Ejector pin,Gate Design,Tunnel gate into ejector pin,Gate Design,Example of a tunnel gate into ejector pin,Material in ground section of ejector pin,Ejector pin whiteness mark,Gate location tunnel breaks away during
18、 ejection,R,R,Gate,Cashew Gate,Knit Line,Gate Area,Knit Line and Gate Area,Process Selection Blow,Valve Gate Shut Off System,A Fills,Bushing A Closes,Gating Location,Gate Location is Strongly Influenced by Glass Content,and/or Crystalinity.End Gating is Preferred in Filled/crystalline Materials to M
19、inimize Warpage.,VENTING,Parting Line,.001-.0025Depth,Gate,Vent,.060 Min.,Note Step,.500,.050Min.,Clearance Around Knockout,.0025,Ejector Pin,“O”RINGENTIRE WORKINGSURFACE,EVACUATE THRUPINS AT RUNNERAND END OF FILLOF EACH PARTOR INTO A DEEPVENT AROUND PART,MAY REQUIREHI TEMP“O”RINGS ON PINS AND SLIDE
20、 AREAS,Vacuum Evacuation,TEMPERATURECONTROL,The Most Efficient Cooling Systems Are Those Which Operate Such That The Inlet and Outlet Coolant Temperatures Are Within 100 Of Each Other,Fluid Velocity Ft./Sec.,Turbulent Flow,Transition Area,Heat Transfer EfficiencyWater Coolant,0.5,1.0,1.5,2.0,Laminar
21、,Flow,IN,OUT,Balanced Cooling Uniform CoolingMaximum Temperature Differential of 10 oF,Flow rate VS.Tool Temp.,Cold Molds Heated Molds,Difficult Fill Higher Injection Pressures Higher Melt Temperature Difficult Ejection(Ejection Stress)Higher Molded-In Stress Tendency for Voids in Thicker Sections,E
22、asier to Fill Lower Injection Pressure Lower Melt Temperature Easier Ejection(Lower Ejection Stress)Lower Molded-In Stress Tendency for Sinks in Thicker Sections Improved Surface,Mold Cooling Series Bubbler,IN,OUT,POOR,Pin,Blade,Mold Cooling Parallel Bubbler,IN,Correct,OUT,Pin,Tube,EJECTOR MECHANISM
23、S,Pin Diameter is as Large as PossiblePins Are as Numerous as PossiblePins Exert a Uniform Force on Molded Parts,EJECTOR MECHANISMS DESIGN,80 to 100 InSidewall ContactPIN DIAMETER1/8”1/4”3/8”,REQUIRESPIN BEARING SURFACE1 in21 in21 in2,1 In PinBearing SurfaceNUMBEROF PINS82209,2,2,Factors Effecting E
24、jection Force,Sidewall DraftSidewall Contact AreaSidewall Polish/TexturingDegree of PackingMold TemperatureMold Release,Blade atDeep Ribs,Rounds Pins,SleeveEjector,Boss,Eject,Mold PinStationary,Parts,Stripper Plate,Stationary Force,Knock OutBars,GOOD KNOCK OUTFOR ROUND PARTS,USED AROUNDPINS&BOSSES,E
25、jecting the Part,Generous draft angles will facilitate part ejection.,Draft Angle,DRAFT ANGLE,DRAFT ANGLE,1/2o MIN,Additional 1 Degree per Mil in Depth of Texture,Draft Angle for Textured Sidewall,Enhances Styling and Aesthetics Reduces Rejects,Texturing Mold Finishes,CORE PULLS,Hydraulic Core Pulls
26、,Cam Actions Slide,Thermoplastics and Shrinkage,Post-Mold Dimensions of Plastic Parts Differ From MoldCavity Dimensions,Vpart,Vmold,lpart,lmold,Sv=,vmold-vpart,vmold,or,EFFECT OF THICKNESS ON SHRINKAGE,0.06,0.125,0.25,2,4,6,8,8,10,12,14,6,0,(VALOX 420),A,B,B,A,-Direction of flow-Cross Flow Direction
27、,Melt Temp,500 F(260 C)Mold Temp,150 F(66 C)Pressure 12,500 psiCycle Time 22 Sec,Thickness,Mils,Shrinkage,Mils/Inch,Shrinkage,Mils/Inch,O,O,O,O,A,B,Mold Design,Tool Design Checklist,Material FlowNonrestrictive sprue Balanced cooling Runner system Cold slug wells No sharp corners in runner system Gra
28、dual size changes Balanced runner system No sharp corners in part Adequate venting Refer to part design checklist for additional items Nonrestrictive gating Acceptable location of weld lines,Cooling High thermal conductivity sprue bushing Balanced cooling Nonrestrictive coolant lines Turbulent flow rateAdequate clearance for coolant lines through tool Adequate cooling for thick part walls,Ejection Adequate stroke Lifter release Adequate draft,
