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1、Thequestionoftestingmould
1.IntroductionInjectionmouldingwithoutrejectsistheidealmoulderstrytoattain.Thisarticledescribestwoauxiliarydevicesthatcouldincreasetherepeatabilityofaninjectionmouldingmachine.Oncetheoptimumparametersareset,thephysicaldimensions,w
2、eightandotherphysicalpropertiesofthepartwillstayalmostconstant.Thetwodevicesdoclampingforcemeasurement/controlandcavitypressureswitchovertoholdingpressure.Forinjectionmouldingofhighprecisionopticalparts,orpartswithahighaddedvaluelikeappliancecases,thepayof
3、fofreducedrejectsishigh.Figure1showsthepartweightdistributionofqualitymouldingandsuboptimalmoulding.Thenominalweightis60g,allowabledeviationis+0.1gand-0.05g.Thewhitecubesdenotepartswithinthetoleranceband.Figure1.Qualityinjectionmouldingandotherwise2.Clampi
4、ngforcemeasurement/controlTheclampingmechanismofinjectionmouldingmachinesfallsmainlyintotwocategories:toggleanddirecthydraulic.Theformerismorewidelyused;thelatterhasthepropertyofautomaticclampingforceregulation.Asaresult,directhydraulicclampmachinedonotnee
5、dclampingforcemeasurement/control.2.1ToggleclampA5-pointdoubletoggleclampisshowninFigure2.Afteramplificationbythetogglemechanism,theclampingcylinder,attachedtothetailplaten,extends,pushingthemovingplatentolockthemouldhalvestogether.Wewillinvestigateinvario
6、uswayshowtheclampingforceisgenerated.Figure2.The5-pointdoubletoggles2.2ClampingforceAtitssimplest,theratedclampingforceFoiscalculatedaccordingtothefollowingformula.Fo=Ps*A*M-------------------------------------------(1)wherePs=systempressure,A=clampingcyli
7、ndercrosssectionalarea,M=mechanicaladvantageofthetoggles.Inmostmachines,Mhasavalueofbetween22and30.Itisafunctionofthetoggledimensionsandthestiffnessofthetogglesandtiebars.2.3RatedclampingforceandadequateclampingforceTheclampingforcefoundinthespecificationt
8、ableofaninjectionmouldingmachineistheratedclampingforceFo.Byconsideringthevariousdesignparameters,themachinedesignercalculatesitusingformula(1).Inusinganinjectionmouldingmachine,itisbesttousetheminimalbutadeq
