Design Guide: Optimizing Parting Line in Injection Molding

A parting line is an inevitable part of injection molded products. It is the line of separation between where two halves of a mold meet. ADesignGuideonOptimizingPartingLinesinInjectionMoldingPostedon:May28,2021ByLeonHuangHome/Blog/ArticleApartinglineisaninevitablepartofinjectionmoldedproducts.Itisthelineofseparationbetweenwheretwohalvesofamoldmeet.Itmanifestsitselfoninjectionmoldedpartsasalinethatrunstheentireperimeterofthepart.Inmostparts,itisjustalinethatrunsstraightdownthemiddle.However,inmorecomplexparts,itslocationvaries.Whileapartinglinemightseemharmless,itisveryimportantindeterminingtheusefulnessofapart.Thisisbecauseitspositionisinfluentialinhelpingdesignersandmolderstodecidewheretoinsertotherfeaturesofthepart.Ifamachinistplacesanimportantfeatureonthewrongsideofthepartingline,itcouldleadtoseriousissueswiththewholeinjectionmoldingprocess.Thisarticlewillfullyexplaintheformationprocessofpartinglines,thedifferenttypesofpartinglineininjectionmoldingandhowtoconsiderthemwhiledesigningyourpart.Staywithustilltheendtofindoutthebestguidetooptimizepartinglines.HowarePartingLinesFormed?Theformationofpartinglinesisaresultoftheinjectionmoldingprocessitselfratherthananyerror.Generally,themoldmachinistsuseforproducinginjectionmoldedpartsisusuallydividedintotwohalves(knownasthefixedhalfandthemovinghalf).Whenthemachinistsclosethemoldbody,themoldhalves(knownasthecoreplates)andthesurfaceofthecavitymakeapartinglinebetweenbothhalvesofthepart. HowPartingLinesareFormedOnmostoccasions,thepartinglineofamoldedproductisperpendiculartotheopeningdirectionofthemoldusedtomaketheproduct. Whenthemachinistopensthemoldandremovesthecooledandsolidifiedpart,themovinghalfofthemoldmovesandseparatesfromthefixedhalf(whichisstationary).Thisexplainsthefullprocessoftheformationofthepartingline.However,machinistssometimesmakethestructureofthemoldbepartedseveraltimesfromvariousdirections.Thisprocedureisknownasmulti-stepparting.TypesofPartingLinesThetypeofpartinglineininjectionmoldinggenerallydependsonthespecificfunctionandstructureoftheplasticpart. However,therearefivemaintypeswhichare:vertical,stepped,inclined,curved,andintegratedpartinglines.1.VerticalPartingLineTheverticalpartingisthemostpopularofallpartinglinesinplasticdesign.Machinistsformtheverticalpartinglineinaperpendiculardirectionfromthemoldopeningdirection.2.BeveledPartingLineTheplasticpartinglineisinabeveledshapehere3.CurvedPartingLineHere,machinistsbuildthemoldtocreateacurvedpartingline.4.SteppedPartingLineHere,machinistsmaketheplasticpartinglineinasteppedshape.Forthistypeofpartingline,there’susuallyalargeforceononesideofthecavity.Thiscausesarelativepossibilityofslidingbetweenthefixedandmovinghalvesofthemold.Thisforcecanthenbecanceledoutbygeneratinganinjectionforceonbothsidesofthecavity.There’salsoapossibilityofthegeneratedforcebeingtoolargeortoosmall.Iftheforceistoosmall,machinistscompensateforitwithaguidepin.Here,theeffectofthesmallerunbalancedinjectionforcemightnotbesignificantonthefinalproduct.However,iftheforceistoolarge,acoupleofsolutionscanbeapplied.Hereareafewexamples:Makeawedge-shapedinsertononesideofthecavity.Thisway,theinsertoffloadssomeoftheinjectionforce.Hence,themoldscanmaintaintherelativepositionbetweenthecavityandthecore.Layoutthemoldsinasymmetricalshape.Thishelpstomaketheinjectionforceappliedtobothsidesbalanced.Thestructureofthemoldshouldalsobemadeascompactaspossibletosupportthesymmetricalarrangement.5.ComprehensivePartingLineAsthenamesuggests,thisisoneofthemostcarefullydonepartinglinesinplasticdesign.Machinistsanddesignersworkonthispartinglinebasedonthestructureoftheplasticpart.Theycouldcombineallotherpartinglinestomakeacomprehensiveplasticpartingline.DesignConsiderationsforPartingLinesThefirstplacetoknowthebestpartinglinetouseforaninjectionmoldedproductisthemolddesign.Insomeparts,thechoiceisobviouswhileitmightnotbesoclearinsomeplaces.Thissectionwilladdresstheimportanceofpartinglinesinplasticdesign.Thefirstconsiderationistodeterminetheopeningdirectionofthemoldrelativetothepart.Machinistscallthisfactor“thelineofdraw.”Itisveryimportantindetermininghowthedesignofthepartwilllooklike.Italsohelpstoknowwhichsidestoaddthefeaturesoftheproduct.Apartfromthis,italsohelpstodeterminehowthevestigesleftbythetwohalvesoftheinjectionmoldedproductwilllooklikeonthefinalproduct.Anotherfactorthatisimportantwhendeterminingthepartinglineiswheretoplacecomponentsonthepart.Thisisbecausetheshrinkingofplasticwhileitcoolsmightshiftthepositionofthepartinthemold.Thiscoulddisplacethefunctionalfeaturesofthepart,renderingituseless.Also,themachinistsshouldensuretheshrinkingpartdoesn’tshrinktoohardtoavoiddifficultejection.Onewaytoensurethecomponentsstayintherightplaceistodraftthewallsoftheinjectionmoldedpartawayfromthepartingline.Themoredraft,thelesstheprobabilityofthefeaturesfallingapart.AnothergoodwaytodeterminethepartlineininjectionmoldingiswithcheckingtheDesignforManufacturability(DfM)ofyourproduct.Apartfromsuggestingthebestpositionsforyourpartline,italsohelpstocheckfordefectsandoptimizeyourpartformanufacture.Thiswillhelpprovideeconomicoptionstomanufacturingyourpart.AtRapidDirect,weprovidefreeDfMforinjectionmoldedproductsonourinstantquotingplatform.However,you’llhavetorequestamanualevaluationforthisfeatureifdesired.ConclusionTakingallthesepartlineconsiderationsintothedesignofyourinjectionmoldedproductisimportant,butthat’snotall.Therearevariousimportantinjectionmoldingguidesandrulesthatyouhavetofollowbeforeyourinjectionmoldingprocesscanbeasuccess.ThisiswhyyoushouldletRapidDirecthandleyourinjectionmoldingprocess.Withawideteamofengineersatyourdisposal,weprovidevariousoptionsandideastoimproveyourpartdesignandmanufacture.Withus,youcanbringyourcustomproductordesigntolifewithinashortperiodoftime.Talktoourengineerstodaytogetthebestinjectionmoldingservicesatyourfingertips!UploadyourInjectionMoldingFileHereLatestBlogWallThickness:UnderstandtheBest3DPrintingWallThicknessWallthicknessisthedistancefromtheexternalparttotheinternalpartofa…Continuereading"WallThickness:UnderstandtheBest3DPrintingWallThickness"What’sWaterjetCuttingProcessWaterjetcuttingisakindofsheetmetalfabricationprocesscuttingnearlyanytype…Continuereading"What’sWaterjetCuttingProcess"GalvannealvsGalvanizedSteel:CompareSheetMetalMaterialsGalvanizationandgalvannealingarecoatingprocessesthatinvolvecoatingasheetmetalpartwithzinc.…Continuereading"GalvannealvsGalvanizedSteel:CompareSheetMetalMaterials"Categories3DPrintingCNCMachiningDesignGuideInjectionMoldingMaterialMedicalInjectionMoldingSheetMetalFabricationSurfaceFinishUncategorizedTryRapidDirectnow,forfreeAllinformationanduploadsaresecureandconfidential.GetaQuoteRelatedarticlesFeb16,2022ThermosetvsThermoplastic:Definition,Processes,andDifferencesReadFullArticleJan18,2022OvermoldingvsInsertMolding:SelectingtheBetterManufacturingProcessforYourProductReadFullArticleDec14,2021MetalPartsManufacturing:HowtoMakeCustomMetalPartsReadFullArticle