注塑零件翘曲变形机理

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1、WarpageWARPAGEWarpagecanbedefinedasadimensionaldistortioninamoldedproductafteritisejectedfromthemoldattheendoftheinjectionmoldingprocess.Warpageissometimescalled``potato-chipping''becausetheparttendstoappearwavy.MachineInadequateInjectionPressureorTimeExplanation:Iftoolittleinjectionpr

2、essureisusedtheplasticmaterialwilltendtocoolandsolidifybeforethemoldispackedout.Ifnopackingisachievedtheindividualmoleculesarenotheldtightlytogetherandhavespacetomovewhilethepartiscooling.Also,iftheinjectionholdtimeisnotlongenough,thepackingprocessisminimizedandthemoleculescanrelaxbefo

3、refullsolidificationoccurs.Ineithercase,asthepartcoolsitisuncontrolledandtheplasticisallowedtomovebecauseitisnotbeingconstrained.Eachareaofthepartcoolsatadifferentrateandwarpagewilloccurduetothedifferences.Solution:Increasetheinjectionpressureortimeapplied.Thiswillensurethetotalpartisc

4、oolingwhileconstrainedandthetendencyforwarpagewillbeminimized.InadequateResidenceTimeExplanation:Residencetimeistheamountoftimeamaterialmustspendbeingexposedtoheatinthebarrel.Thetimeisdeterminedbytheabilityofthespecificresintoabsorbheatenoughtobeproperlyprocessed.Inadequateresidencetim

5、ewillresultinunder-heatedmaterial,whichcausesthematerialtobestiff.Itwillcooloffbeforethemoldispackedandindividualmoleculeswillbeunconstrainedwhiletheysolidify.Moleculesthatarenotconstrainedduringcoolingwillshrinkatdifferingratesthroughoutthepartandwarpagewilloccur.Solution:Increasether

6、esidencetimebyaddingtimetothecoolingportionofthecycle.Whileincreasedcycletimemayaddcosttothefinalproduct,eachmaterialrequiresaspecificminimumamountoftimetoabsorbheatinthebarrel,andifthetimeisnotlongenoughwarpedpartswilloccur.BarrelTemperatureTooLowExplanation:Whenbarreltemperaturesaret

7、oolow,thematerialwillnothaveachancetoheattotheproperflowtemperature.Thecoldmaterialgetspushedintothemoldbutsolidifiesbeforethemoleculesarepackedandconstrained.Thisresultsinwarpageasthemoleculesshrinkatvaryingrates.Solution:Increasethebarreltemperature.Thiswillallowthematerialtocometo