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1、Airtraps困氣Whatisanairtrap?Anairtrapisairthatiscaughtinsidethemoldcavity.Itbecomestrappedbyconvergingpolymermeltfrontsorbecauseitfailedtoescapefromthemoldvents,ormoldinserts,whichalsoactasvents.Air-traplocationsareusuallyinareasthatfilllast.Lackofventsor
2、undersizedventsintheselast-to-fillareasareacommoncauseofairtrapsandtheresultingdefects.Anothercommoncauseisrace-tracking(thetendencyofpolymermelttoflowpreferentiallyinthickersections),causedbyalargethicknessratio.困氣是氣體存在于模具型腔內無法排出，困氣會形成氣孔是其聚集在熔體前端或未從模具排
3、氣孔以及鑲件排出。困氣通常發生在最終填充位置。在填充末端缺少排氣孔或排氣孔太小都會引起空位造成制品缺陷。另一個較為普遍的原因是跑馬場效應（聚合物熔體有優先向肉厚方向流動的趨勢），是由于壁厚突變引起的。FIGURE1.Airtraplocationsindicatedbythecomputer-predictedmelt-frontadvancements.(Toreplaytheanimation,clickReplay)ProblemscausedbyairtrapsEntrappedairwill
4、resultinvoidsandbubblesinsidethemoldedpart,ashortshot(incompletefill),orsurfacedefectssuchasblemishesorburnmarks.Toeliminateairtraps,youcanmodifythefillingpatternbyreducingtheinjectionspeed,enlargingventing,orplacingproperventinginthecavity.困氣將引起成型制品內部空
5、位和氣泡，短射（澆不足），或表面缺陷如污痕或燒焦。可以利用改善成型條件來解決困氣問題，如減少注射速度，擴大排氣孔，或者適當位置開設排氣孔。Inthefigurebelow,anairtrapresultsfromrace-trackinginapartwithalargethicknessratio.Inthiscase,theentrappedaircanbeventedbychangingthethicknessratioorbyplacingavent(e.g.,viaanejectorpin)
6、attheairtraplocation.以下的例子中，困氣是由于壁厚突變產生的跑馬場效應引起的。困氣可以由減小壁厚變化率或者適當位置開設排氣孔消除。Remedies補救措施Alterthepartdesign改變零件的設計Reducethethicknessratio.減少壁厚變化Thiswillminimizetherace-trackingeffectofpolymermelt.可以減少聚合物熔體的跑馬場效應。Alterthemolddesign改變模具的設計Paycloseattentiont
7、otheproperplacementofyourvents.密切關注開設排氣孔位置Placeventsintheareasthatfilllast.在熔體流動末端開設排氣槽Ventsaretypicallypositionedatdiscontinuitiesofmoldmaterial,suchasatpartingsurfaces,betweentheinsertandmoldwall,atejectorpins,andatmoldslides.排氣孔通常開設在模具中斷處，比如分型面、鑲件與模具
8、間隙、頂針、滑塊等。Re-designthegateanddeliverysystem.重新設計澆口和澆注系統Changingthedeliverysystemcanalterthefillingpatterninsuchawaythatthelast-to-fillareasarelocatedattheproperventinglocations.改變澆筑系統可以改變充填形式使得流動末端布置好排氣。Makesuretheventsizeislarge
