tooling_English_模具英语第二章

《tooling_English_模具英语第二章》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。

1、Lesson2MouldforThreadedComponentsItisfrequentlynecessarytodesignamouldforacomponentwhichincorporatesathread.Athreadisaformofundercutwhichnormallyincreasestheintricacyofthedesign.Theextentofcomplicationvariesanditisdependentonanumberoffactors,namely:(i)typeofthread:internal,external,continuou

2、sordiscontinuous;(ii)method:threadformmoldedorincorporatedbytheuseofametalinsert;(iii)typeofproductions:manual,semi-automaticorfullyautomatic.MouldsforinternallythreadedcomponentsTheinternalthreadcomeswithinthebroaddefinitionofaninternalundercutinthatthethreadformsarestrictionwhichpreventsth

3、estraightdrawremovalofthemoldingfromthecore①.Thereareanumberofalternativedesignsofmouldtoconsider,andforreferencethesearesummarizedasfollows:(i)singleinterruptedthreaddesign;(ii)strippingthreaddesign;(iii)splitcoredesign;(iv)fixedthreadedcoredesign;(v)loosethreadedcoredesign;(vi)collapsiblec

4、oredesign;(vii)unscrewingmoulddesign.StrippinginternalthreadsTheinternallythreadcomponentmaybestrippedfromthecoreusingthebasicstripperplatedesignprovidingtheplasticmaterialhassufficientelasticityduringtheejectionphase②.Thesameprincipleapplieshereastostrippinganyinternalundercut,i.e.themoldin

5、gmustbefreetoexpandduringejectiontopermitthemoldedundercuttorideovertherestrictiononthecore③.Thismeansthattheoutsideformofthecomponentmustbesuchthatitcanbeformedinacavitywhichisfullycontainedinonehalfofthemould.AmouldofthistypeisillustratedinFigure2-1.Thisdiagramshowsasingleimpressionmouldfo

6、raninternallythreadedcap.Figure2-1StrippinginternallythreadcomponentsThemouldopensinitiallyand,becauseofmoldingshrinkageandtheundercutform,themoldingiswithdrawnfromthecavity.Duringthelatterstagesofopeningthestripperplate’smovementischecked,therebycausingthesecondopeningtooccuratB.Themoldingi

7、s,therefore,progressivelystrippedasthecoreiswithdrawnthroughthestripperplate.Theapertureinthestripperplatemustbeslightlylargerindiameterthanthemajordiameterofthethreadinordertopreventscoringofthethread.CollapsiblecoreThecollapsiblecoredesign,whichi