分析注塑中产生的气泡-空洞-水纹解决方案

分析注塑中产生的气泡分析注塑中产生的气泡,空洞，水纹解决方案Theappearanceofbubbles,voids,sinksorTheappearanceofbubbles,voids,sinksorblistersonaninjection-moldedpartmakeupthemostsignificantcausesforpartrejectsduetocosmeticrequirements.Thesetroublesome“features“,althoughnotthemostcommonofproblemswheninjection-moldingparts,caninhibitpartperformanceandareproblematictosolve.Bubblesareeitherpocketsoftrappedgasorvacuumvoids.Itisimportanttodeterminewhichtypeofbubbleexistsinyourparttomorequicklypinpointthesourceanddeterminethecorrectadjustmenttomake.Asimpletestofwarmingthepartareacontainingthebubbleuntilitsoftenscanbeusedtodetermineitsbubbletypeastrappedairorvoid.Withthetest,ifthereisgastrappedinthebubble,thegaswillwarmupandwanttoexpandthebubbleasthepartsoftens.Ifthereisnoairinthebubbleandavacuumvoidexists,thebubblewillcollapseduetotheatmosphericpressurepushingonthesoftenedwallsofthepart.Ahotairgunisbesttoheatthearea,asmalllighterisnext,andatorchifyouknowwhatyouaredoing.TrappedAirIssueTrappedairisarootcauseofbubblesaswellasblisters.Trappedgasmaystemfromflowfrontissuessuchasconvergingfronts,orjetting,toequipmentandproductionproblemssuchasnon-ventedcorepins,poorventing,toomuchdecompression,orresindegradation.Theairorgasmayappearfromwatervapor,volatilesfromtheresin,ordecomposingby-products.Theairmaybetrappedinribs,threadsornon-vented1/72/7projectionsoffthenominalwall.Meltflowpatternisamajorcauseofbubbles.Processorsshouldexamineeachpartsflowpatternviashortshotstoseeiftheplasticflowfrontiscomingaroundonitself.Noteifthereisarace-trackingeffectorjettingthatcancauseairtobecometrappedinthepolymer.Observeflowpathforbackflowortrappedairinblindribs.Examinetheparttodetermineiftheriborsupportareasofapartarecoveredbeforepartiscompletelyfilled.Ifitisaflowpatternissue,runashortshotmoldingsequence,changingthetransferpositionorshotsizetomakevarioussizedshortshotpartsrangingfrom10percentto95percentofthefullpart.Usethistofindoutwhereandhowthebubbleoccurs.Thistestrequirestheprocesstobevelocitycontrolledforthefirststage(injection).Thiscannotbedoneifthefirststagepressureandvelocityisreduced.Othercausesfortrappedairleadingtobubblesorblistersincludeinadequateventing,materialflowpatterndesign,andgastravelingacrossthepartsurfaceduringthefillorpackstage.Meltflowissuesmayindicateaneedtochangethegatelocationtoavoidracetracking,trappingairortopromoteuniformfillingEquipmentcanalsobeacauseforbubbles.Ifyouareworkingwithahotrunnertoolitispossiblethataventurieffectcansuckairfrombetweentheplatesintothehotrunner,pullingairintothemelt,formingabubble.Tocheckforthisthetoolmustbedisassembled,andabluingagentisappliednearthedrops,beingcarefulnottoapplyanyintheflowpath.Ifthebluingagentshowsupinthepartthenyouhavefoundthesourceoftheproblem.Onecanalsoexaminethepurgingofanormalshottoseeifthebubbleoriginatesfromthebarrelorscrew.General-purposescrewswithdimensionsof18:1L/Dorlowercanbetheculpritsforabubbleorblister.Onesolutionistoraisethebackpressureto1000to1500psimeltpressure.Anothersolutionmaybetopullavacuumonthemoldjustbeforeinjection,sothatairispulledout.Moistureinthemoldingsystemcanalsobeasourceoftrouble.Toolventingisanotherbigissue,soventproperlyoruseaporoussteeltoeliminategastraps.Checkthenumberofventsaswellasventdepth.Checkventswithpressuresensitivepaper.Cleanallpartinglineandcorevents.Thiscanpreventtheopportunityfortrappingair.AvoidingVoidsandSinksAvoidoccursduringcooling,usuallyinthicksectionsofthepartwheretherecanbeasignificantcoolingratedifferenceinthematerialformingthecoreandskinofthepart.Asinkisadepressionimpactingthesurfaceofapartthatdoesnotmimicthemoldsteelsurface.Voidsandsinksaresignsofinternalstressandarewarningsignsthatthepartmaynotperformasrequired.Insufficientplasticcanbeamainreasonforsinksorvoidssopackingmoreplasticintothecavityisrecommended.Moldersshouldhaveaconsistentcushiononthepress,makingsureyouarenotbottomingoutthescrew.Youshouldgoforhigherpressuresinthehold/packstageandlongerstagetime.Tosolvevoidsorsinks,trialslowfillrates,theuseofgascounter-pressure,andincreasingbackpressure.Youcanopenthegateforlongergatesealtimestoallowmorepackingduringthesecondstage.Molderscanalsotryreducingthemelttemperature.Mechanically,youcanincreasetherunnerdiameter.Youshoulddeterminewherethesinkis.Isitnearthegateorfartherdowntheflowpart?Ifnearthegate,checkthegatesealtime.Ifitisfartherdowntheflowpart,increaseinjectionspeedtodecreaseviscosityandallowmorepackingpressure.Anotherapproachtoeliminatingvoidsorsinksisto“thin-up“thenominalwall.Thickerisnotalwaysstrongerinplasticparts.Thicknominalwallsshouldberedesignedwithribsifstrengthisneeded.Thiswillsaveplasticandcycletimealso.Molderscancoreoutthethicksectionifpossible.Changingthegatelocationtofillthickerareasinthemoldfirst,thismayallowmorepolymerintothepart(beforethegatefreezes).Moldersmayalsotryraisingthemoldtemperaturesignificantlyand/orejectingthepartsooner,whichcanavoidvoidsbyallowingtheoutsidewallstocollapseduringcooling.Forsinks,usersmaytrycoolingthepartinwaterorbetweenaluminumsheetsratherthanair.Here,innersectionofthethick-sectionedpartcanreheatorre-melttheoutsidesurfaceofthepartonceejected,allowingthesurfacetocollapse.However,thismaycauseavacuumvoid.Youmightbeabletodiminishthevacuumvoidbynotcoolingthepartsurfaceandkeepingitwarmbyplacingonwoodorinsulatingfoam.Oneshouldexpectsinkswiththisapproach.BeAwareofBlistersBlisters,athinfilmofplasticthatbubblesupfromthepartsurface,canalsoruintheaestheticsofapart.Likebubblestheycanbecausedbygastravelingacrossthesurfaceduringfillorpack,orduetotrappedairissues(inadequateventing,meltflowpatternorscrewL/D),andthesolutionsarethesame.However,blisterscanalsooriginatefromprocessproblemsordegradationoftheresinoradditivepackage.Delaminationisaseriouspartdefect.Excessivelyhighinjectionratescancauseblisters,astheycandevelopahighlyorientedthinlayerorfilmonthesurfaceofamoldedpart.Sometimesstickingtapetothepartandliftingitpullsthislayeroff.Tryinjectingthemeltataslowerrate.Hightemperaturesofsteelnearthegatecancauseblistersalsoandshouldbemadelowerifpossible.Ifthedecompressionofthescrewisexcessive,itispossiblethatairwillbepulledintothenozzleandremainstrapped.Thisairpocketentersthemeltstreamduringnozzlecontactwiththesprue.Ifusingahotrunnersystem,atinjection,thetrappedairismovedthroughthehotrunnersystemandcancreatethebubble.Inacoldrunnersystemtheairisaheadoftheflowfrontandgetsvented.GasGascanbecreatedbythedegradationoftheresinoradditive,sotryanewlotofmaterialand/orusevirginmaterial.Itisbesttocheckthemelttemperatureprocessrangerecommendedbytheresinsupplier.Moldersshouldminimizematerialresidencetime,andonewayistousethecorrectbarrelsizefortheshot.Besurethattheplasticatingscrewbeatleast20:1L/D.Ifyouarerequirelongercycletimesandhigherbackpressuretoreducetheoccurrenceofblisters,thenitispossiblyascrewdesignissue.消退气泡，空洞，水槽和水泡消退气泡，空洞，水槽和水泡对注塑成型零件的气泡，空洞，水槽或水疱的消灭弥补了局部因拒绝整容要求最显著的缘由。这些麻烦的“功能”，虽然不是最常见的问题，当注塑件，可以抑制一局部的性能和有问题要解决。气泡被困气体或真空空隙或者口袋。重要的是要确定哪些在你的一局部存在泡沫型更快速查明来源，并确定正确的调整，使是很重要的。直到它软化升温含有气泡的局部区域的一个简洁的试验可以用来确定它