塑膠產品模具設計

第六章塑料產品與模具設計PlasticPartandMoldDesign澆注系統(tǒng)設計FillingSystemDesign模具設計的優(yōu)先順序PrioritiesofMoldDesign澆注系統(tǒng)設計(FillingSystemDesign)排氣系統(tǒng)設計(VentingSystemDesign)冷卻系統(tǒng)設計(CoolingSystemDesign)脫模系統(tǒng)設計(EjectingSystemDesign)澆注系統(tǒng)設計的優(yōu)先順序PrioritiesofFillingSystemDesign產品設計(PartDesign)型腔設計(CavityDesign)澆口設計(GateDesign)流道設計(RunnerDesign)豎澆道設計(SprueDesign)噴嘴設計(NozzleDesign)豎澆道Sprue主流道MainRunner成品Part澆口Gate冷料井ColdSlugWell支流道BranchRunner典型的澆注系統(tǒng)TypicalFillingSystem壁厚不均是注塑成形中最大的麻煩制造者。這對薄壁零件尤然。這些麻煩包括了遲滯現象、短射、凹陷、發(fā)赤、噴流、翹曲及長冷卻時間等；目前都可用CAE以直接或間接的方式預測。Non-uniformwallthicknessisthebiggesttroublemakerinplasticinjectionmolding.Thisisespeciallytruetothin-wallpart.Thetroubles,includinghesitation,shortshot,sinkmark,blush,jetting,warpageandlongcoolingtimeetc.,canbepredicted,directlyorindirectly,byusingCAE.壁厚不均

Non-uniformWallThickness壁厚設計WallThicknessDesign差[Poor]較好[Better]最好[Best]掏空設計(1)CoringOutDesign(1)改進設計

[Improved]原設計

[Original]差[Poor]改進

[Improved]掏空設計(2)CoringOutDesign(2)氣泡或/和凹陷的形成Voidor/andSinkMarkForming氣泡

(Void)凹陷

(SinkMark)肋厚和內圓角半徑的影響TheEffectofRibThickness&FilletRadius肋的底部厚度BottomThicknessofRibW0.5W2.5WW1.2WD1.5WD(A)(B)肋的設計(一)RibDesign(1)t =wallthichnessB=0.5tC =3tAAD=2BE=0.13mm(radius)F=1.5-2deg假如需要更大的強度,可增加肋的數目Ifmorestrengthisrequired,addadditionalribs.FBDECt

肋的設計(二)RibDesign(2)肋的設計(三)RibDesign(3)與側壁相連之凸殼(熱塑性塑料)BossatWall(Thermoplastics)A =凸殼附著處壁厚

wallthicknessB =凸殼外環(huán)直徑

dia.ofbossoverradiiC =0.5AD =2BE =1~2degF =0.13mm(radius)G =DH =0.8AI =A/4J =2BK =0.3~1JL =0.5ALHA'A'KEIGJDAFCBSectionA'-A'遠離側壁之凸殼(熱塑性塑料)BossAwayFromWall(Thermoplastics)A =凸殼附著處壁厚

wallthicknessB =凸殼外環(huán)直徑

(含底部修整圓弧半徑)

dia.ofbossoverradiiC=0.5AD=2BE =1-2degF =0.13mm(radius)G=0.95DH=0.3Gmin.toGmax.I =0.5AHEFDFGCBAI外側凸殼OutsideBoss

A'A'A(DIA)BB=AB=2A(max.)SectionA'-A'Where1/r :樑的曲率

curvatureofthebeamM :彎曲力矩

bendingmomentE :彈性模數

modulusofelasticityI :斷面積對中立軸的慣性矩

momentofinertiaofthecross-sectionalareawithrespecttotheneutralaxisEI :翹曲剛性

flexuralrigidity撓曲剛性

FlexuralRigidityNeutralAxis?10.8平板和肋板的比較

ComparisonbetweenPlain&RibbedPlates和平板比，若基于相同的慣性矩(剛性)，肋板需料少了43%，I/A卻增加了1.79倍。肋板的最大厚度減為平板的1/4，使得冷卻時間驟降15/16(94%)。Basedonthesamemomentofinertia(stiffness),ribbedplateneeds43%lessmaterialbutboostI/Aby1.79timescomparingwithplaneplate.Themaximumthicknessofribbedplateisonly1/4ofplainplate＇s;showingadramaticcoolingtimereductionof94%(15/16).平板和肋板的比較

ComparisonbetweenPlain&RibbedPlatesAvarietyofmolded-ininterlockscanaddstiffnesstothin-wallhousingdesigns.各種一體成形的內鎖件能增加薄殼的剛性。結構設計是薄殼成形零件的基礎。Structuraldesignisthebaseofthin-wallmoldingparts.薄殼成形零件不僅僅是一趨勢，而且也是降低成本和提高競爭力的有效途徑。Thin-wallmoldingpartisnotonlyatrendbutalsoaneffectivewaytoachievecostreductionandcompetitivenessincrease.結構設計和薄殼成形零件StructuralDesign&Thin-wallMoldingParts每增加一個澆口，至少增加一條熔接線，同時增加一個澆口痕跡、增加流道的體積以及增加較多的積風。Everytimeonegateisadded,oneweldline,atleast,onegatemark,morerunnervolumeandmoreairtrapswillbeadded.在型腔能夠完滿充填的前提下，澆口數目是愈少愈好。Aslongasthecavityisabletobefilledappropriately,gatesarethelessthebetter.為了減少澆口數目，每一澆口應就塑流力所能及的流長/壁厚比之內，找出可以涵蓋最大零件面積的進澆位置。Inordertoreducethenumberofgates,eachgateshallbelocatedatwherethemeltisabletocovermaximumpartareabasedonthelargestmeltflowlength/thicknessratio澆口數目TheNumberofGates熔膠波前推進Melt-FrontAdvancement充填方式,積風和熔接線FillingPatterns,Air-TrapsandWeldLinesLocation熔接線WeldLines材料[Material]:PC-GF50原設計[Original]更改設計[Revised]更改澆口位置以重新定位熔接線WeldLinesCanBeRelocatedByChangingGateLocation典型對頭熔接線伸張強度保留值TypicalButtWeldTensileStrengthRetentionValues熔接線冷料井WeldSlugWell對頭熔接線[Buttweld]熔接線冷料井[Weldslugwell]積風AirTraps排氣Vent大部份熱塑性塑料MostThermoplastics A0.08mm B3.18mm C12.7mm D0.25mm耐隆和聚縮醛(POM)NylonandAcetal(POM) A0.04mm B3.18mm C12.7mm D0.25mm進料流道FeedRunner塑料成品PlasticPartAD排氣孔VentBSEC.A'-A'CA'A'充填均衡FlowBalance熔膠波前于同一時間抵達型腔各末端。Meltfrontreachestheendsofcavityatthesametime.原始設計OriginalDesign十二澆口設計12GateDesign電子零件置物箱材料Material：ABS四澆口設計4GateDesign修正設計RevisedDesign電子零件置物箱材料Material：ABS電子零件置物箱四澆口和十二澆口設計比較表剪切速率ShearRate剪切應力shearStress黏度viscosity剪切速率shearrate剪切應力ShearStress澆口種類GateTypes針點澆口PinGate扇型澆口FanGate潛伏澆口SubmarineGate邊緣(薄膜)澆口Edge(Film)Gate凸片澆口TabGate閥澆口ValveGate環(huán)狀澆口RingGate導致平直零件的澆口設計GateDesignforFlatPart中心澆口CenterGate扇形澆口FanGate最壞的Worst壞的Worse較好的Better最好的Best側澆口EdgeGate薄模澆口FilmGate澆口設計(減少滯流效應)GateDesigntoAvoidHesitation澆口gate薄thin厚thick差的設計Poor好的設計Good薄thin厚thick澆口gate澆口設計(避免凹陷和氣泡)GateDesigntoAvoidSinkMark&Void澆口gate澆口gate差的Poor好的Good使用重疊澆口以避免噴流AvoidJettingbyUsingOverlapGate差的Poor好的Good正確的澆口位置以避免噴流AvoidJettingbyLocatingGateCorrectly差的Poor好的Good使用凸片澆口以避免噴流AvoidJettingbyUsingTabGate使用適當的澆口形狀以避免噴流AvoidJettingbyProfilingGateProperly差的Poor好的Good泵零件(Part,Pump)塑料(Polymer):POM進澆處(Polymerentrance)：澆口厚(Gatethickness)1.2mm，模穴厚(Cavitythickness)3.2mm問題(Problem)：噴流(Jetting)PoorDesignCausingJettingGatePart :Handle,RefrigeratorMaterial :ABSProblem :JettingMarkGasPin氣輔成型冰箱把手澆口及氣針入口澆口太小,導致噴流痕產生厚度差異過大,導致二次噴流痕產生R角過小,氣體通路接近把手內側,外側則因體積收縮造成凹陷痕跡閥澆口ValveGate1.閥澆口梢

Valve-GatePin2. 加熱管Heater3. O型環(huán)#610"0"Ring4. 流道歧管模板ManifoldPlate5. 軸封環(huán)

SealRetainer6. 套筒軸封

SleeveSeal7. 枕塊SupportPillar8. 油壓缸

HydraulicCylinder閥澆口(一)ValveGate(1)全部閥澆口同時打開時之充填狀況Moldfillingwithallthevalvegates(shut-offgates)openedatthesametime.閥澆口(二)ValveGate(2)部份閥澆口推遲打開，改變充填方式Moldfillingwithdelayedvalvegateopening;fillingpattern,weldlinesandairtrapsarechanged.多澆口設計

Multi-GateDesign閥式澆口ValveGate矩形邊緣澆口設計RectangularEdgeGateDesignL=0.5~0.75mmW=澆口寬度(mm)gatewidthinmmA=型腔表面積(mm

)surfaceareaofcavityinmmn=材料常數materialconstant0.6forPE,PS0.7forPOM,PC,PP0.8forCA,PMMA,PA0.9forPVC22h=nth=澆口厚度(gatethick.inmm)t=零件壁厚(wallthick.inmm)WtLh扇形澆口設計FanGateDesignL=1.3mmW=w=澆口寬度[mm]gatewidthinmmA=型腔表面積[mm]surfaceareaofcavityinmmn=材料常數[materialconstant]0.6forPE,PS0.7forPOM,PC,PP0.8forCA,PMMA,PA0.9forPVC澆口厚度[gatethick.inmm]t=零件壁厚[wallthick.inmm]

2

2

h1=nt

h2=wh1/D重疊式澆口設計OverlapGateDesignW=w=澆口寬度[mm]gatewidthinmmA=型腔表面積[mm]surfaceareaofcavityinmmn=材料常數[materialconstant]0.6forPE,PS0.7forPOM,PC,PP0.8forCA,PMMA,PA0.9forPVC澆口厚度[gatethick.inmm]=nt澆口長度[landlengthinmm]t=零件壁厚[wallthick.inmm]

2

2

L1=0.5~0.75L2=h+(w/2)凸耳澆口設計TabGateDesignL=0.5~0.75mmW=w=澆口寬度[mm]gatewidthinmmA=型腔表面積[mm]surfaceareaofcavityinmmn=材料常數[materialconstant]0.6forPE,PS0.7forPOM,PC,PP0.8forCA,PMMA,PA0.9forPVC澆口厚度[gatethick.inmm]t=零件壁厚[wallthick.inmm]

2

2

h1=nth2=0.9tL=0.5~0.75mmd=澆口直徑(mm)gatediameterinmmt=零件壁厚(mm)wallthick.inmmA=型腔表面積(mm)surfaceareaofcavityinmmn =材料常數materialconstant0.6forPE,PS0.7forPOM,PC,PP0.8forCA,PMMA,PA0.9forPVC針點澆口設計PinGateDesigndLt潛伏式澆口設計SubgateDesignW=w=澆口寬度[mm]gatewidthinmmA=型腔表面積[mm]surfaceareaofcavityinmmn=材料常數[materialconstant]0.6forPE,PS0.7forPOM,PC,PP0.8forCA,PMMA,PA0.9forPVC澆口厚度[gatethick.inmm]=ntt=零件壁厚[wallthick.inmm]

230~15o~25o

2水力直徑

HydraulicDiameterWhereDHisthehydraulicdiameter水力直徑

Aisthecross-sectionalareaoftheflow流路斷面積

Pisthewettedperimeter濕周長水力直徑

HydraulicDiameter在不同剖面形狀，相同斷面積下之變化Variousrunnerprofiles,basedonthesamecross-sectionalarea流道尺寸設計(1)RunnerSizing(1)D :流道直徑(mm) runnerdiameterinmmW :下游塑料重量(g) downstreamplasticweightL :流道長度(mm) runnerlengthinmm流道尺寸設計(2)RunnerSizing(2)流道尺寸設計(3)RunnerSizing(3)流道尺寸設計(4)RunnerSizing(4)流道尺寸設計(A1)RunnerSizing(A1)G :重量

weightS :零件厚度

thicknessD' :參考直徑

referencediameterG(g)

D'(mm)forPS,ABS,SAN,CAB流道尺寸設計(A2)RunnerSizing(A2)

G(g)

D'(mm)forPE,PP,PA,POMG :重量

weightS :零件厚度

thicknessD' :參考直徑

referencediameter流道尺寸設計(B)RunnerSizing(B)D':參考直徑

referencediameterL :長度

lengthfL:長度系數

LengthcoefficientD :流道直徑

runnerdiameterfLL(mm)D=D'?fL冷料井設計ColdSlugWellDesign2d次流道Secondaryrunnerd主流道Primaryrunner澆口Gate型腔Cavity倒椎度冷料井豎澆道拉料桿Reversetapercoldslug-wellspruepullerZ型冷料井豎澆道拉料桿"Z"-tapercoldslug-wellspruepuller溝型冷料井豎澆道拉料桿Groovedcoldslug-wellspruepuller冷料井設計ColdSlugWellDesign澆道襯套尺寸SprueBushingSizing排氣系統(tǒng)設計VentingSystemDesign為何排氣仍然還是一個問題？Whyventingisstillaproblem?因為降低射速，讓積風有較多的時間逃氣，是一件太容易的事。但是…Becauseitistooeasytoslowdowntheinjectionspeedandgivethetrappedairmoretimetoescape.But...排氣Vent射速一降，熔膠溫度很快降低，射壓必須提高，殘余應力隨之提高，翹曲的可能性增加。如果想藉提高料溫，以降低射壓，料溫必須升得很高，這樣又會引起塑料裂解。Wheninjectionspeedislower,melttemperaturegoesdownveryfast,injectionpressurehastobeincreased,residualstressisincreasedandthepossibilitygettingwarppagebecomeshigher.Ifonewouldliketoincreasebarreltemperaturetoreducetherequiredinjectionpressure,thebarreltemperaturehastobeincreasedtoaquitehighlevelandpolymerdegradationwouldbeinduced.排氣Vent高料溫和高射壓都說明充填系統(tǒng)有了流動的問題Bothhighbarreltemperatureandhighinjectionpressureareindicationsofflowprobleminthefillingsystem.排氣Vent我們常發(fā)現:射速提高時，塑料表現得更為出色。Itisquitecommonthatmaterialperformsbetterwhenitisinjectedfaster.最適化螺桿速度充分運用摩擦熱，將塑流保持在最佳狀態(tài)。許多充填和翹曲的問題也就迎刃而解。Anoptimizedramspeedprofilefullyusesthefrictionheattokeepthebestflowcharacteristics,whichcorrectsmanyofthefillandwarpageproblems.排氣Vent有了適當的排氣，射速可以提高，充填和保壓可達良好狀態(tài)，不須過度增加料管和噴嘴的溫度。Withproperventing,theinjectionspeedcouldbeincreasedtoachievegoodfillandpackconditions,withouthavingtoraisethebarrelandnozzleheats,improperly.排氣Vent深度(depth): 1.0.075mm易流塑料(easy-flowmat.) 2.0.125mm難流塑料(stiffer-flowmat.) 3.深度深到流道末端見毛邊為準

(deepenoughtofeelflashatrunnerend)寬度(width):和流道同寬(aswideasrunnerdia.)排氣唇部(ventlip):1.5mmA1拋光(finish)排氣通道通大氣(ventchanneltoatmosphere): 1mm深(deep)流道排氣RunnerVents深度(depth):參照廠商建議(refertomanufacturer’srecommendation)寬度(width):全圓周長(wholeperimeter)or5mm長度(length):1.5mmA1拋光(finish)排氣通道通大氣(ventchanneltoatmosphere):1mm深(deep)分模面排氣PartingLineVents深度(depth):參照廠商建議(refertomanufacturer’srecommendation)寬度(width):全圓周長(wholeperimeter)長度(length):1.5mm排氣溝(ventgroove):1mm深(deep)頂出銷或心型銷排氣EjectorandCorePinVents冷卻系統(tǒng)設計CoolingSystemDesign模具冷卻設計的目的PurposesofMoldCoolingDesign1.均衡冷卻(改良產品品質) EvenCooling(ImprovePartQuality)2.有效冷卻 (提高生產力) EfficientCooling(IncreaseProductivity)薄殼產品不像傳統(tǒng)壁厚者一般可以承受較大的因熱傳不均而產生的殘余應力。為了將收縮彎翹控制在可以接受的程度，均衡的冷卻設計變得非常重要。Thin-wallpartcannotaffordasmuchthermalinducedresidualstressastheconventionalonedoes.Anevencoolingdesignbecomesveryimportanttocontroltheshrinkageandwarpageatanacceptablelevel.冷卻設計

CoolingDesign射出成型周期時間InjectionMoldingCycleTime充填時間FillTime開模時間OpenTime后充填時間Post-fillTime對冰箱水果蔬菜盤之類的大零件而言，材料往往占成本50%以上。對小而薄的零件而言，成形機費用可占成本的90%，材料6%，而模具只占4%。小而薄的產品較之厚者更能從冷卻的改善而獲得效益。Forlargermoldedparts,materialtypicallyrepresentsmorethan50%ofthepartcostforarefrigeratorcrispertray.Inthecaseofathin-wallsmallpart,thepresscostcouldbe90%ofthecostofthepart;materialconstitutes6%andthemoldonly4%ofthecostofeachpart.Smallthin-wallpartstypicallybenefitfromimprovedcoolingmorethanthickparts.冷卻設計

CoolingDesign典型的冷卻系統(tǒng)TypicalCoolingSystem模溫調節(jié)機Temperaturecontrollingunit軟管Hoses冷卻回路2CoolingCircuit2冷卻回路1CoolingCircuit1泵Pump收集歧管Collectionmanifold供給歧管Supplymanifold模具冷卻管路

MoldSchematic冷卻孔道CoolingChannels入口Inlet出口Outlet入口Inlet出口Outlet噴泉管Bubbler障板管Baffle熱管HeatPipe蒸發(fā)部位熱輸入HeatIn凝結部位熱輸出HeatOut液體Liquid蒸汽Vapor燈心(毛細管)Wick(Capillary)熱管的應用TheApplicationOfHeatPipe理論上最短冷卻時間Min.PossibleCoolingTime理論上最短冷卻時間themin.possiblecoolingtime產品最大厚度themax.partthickness熔膠的熱擴散度thermaldiffusivityofthemelt射出溫injectiontemp.冷卻液溫度coolanttemp.頂出溫度ejectiontemp.冷卻時間和厚度分布CoolingTimeandThicknessProfile差的設計BadDesign好的設計GoodDesign冷卻孔道直徑、深度和節(jié)距建議值RecommendedDiameter,Depth&PitchD:直徑為10至14mmDiameterofCoolingChannel,10to14mmd:深度為D至3D