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1、模具专业英语Lesson1TheInjectionMoldingandMachineInjectionmoldingisprincipallyusedfortheproductionofthethermoplasticparts,althoughsomeprogresshasbeenmadeindevelopingamethodforinjectionmoldingsomethermosettingmaterials.TheinjectionmoldingTheproblemofinjectingamelt
2、edplasticintoamoldcavityfromareservoirofmeltedmaterialhasbeenextremelydifficulttosolveforthermosettingplasticswhichcureandhardenundersuchconditionswithinafewminutes①.Theprincipleofinjectionmoldingisquitesimilartothatofdie-casting.Theprocessconsistsoffeedin
3、gaplasticcompoundinpowderedorgranularformfromahopperthroughmeteringandmeltingstagesandtheninjectingitintoamold②.Afterabriefcoolingperiod,themoldisopenedandthesolidifiedpartejected.Injection-moldingmachinescanbearrangedformanualoperation,automaticsingle-cyc
4、leoperation,andfullautomaticoperation.Theadvantageofinjectionmoldingare:(i)ahighmoldingspeedadaptedformassproductionispossible;(ii)thereisawidechoiceofthermoplasticmaterialsprovidingavarietyofusefulproperties;(iii)itispossibletomoldthreads,undercuts,sideho
5、les,andlargethinsections.Theinjection-moldingmachineSeveralmethodsareusedtoforceorinjectthemeltedplasticintothemold.Themostcommonlyusedsysteminthelargermachinesisthein-linereciprocatingscrew,asshowninFigure1-1.Thescrewactsasacombinationinjectionandplastici
6、zingunit.Astheplasticisfedtotherotatingscrew,itpassesthroughthreezonesasshown:feed,compression,andmetering.Afterthefeedzone,thescrew-flightdepthisgraduallyreduced,forcingtheplastictocompress.Theworkisconvertedtoheatbyshearingtheplastic,makingitasemifluidma
7、ss.Inthemeteringzone,additionalheatisappliedbyconductionfromthebarrelsurface.Asthechamberinfrontofthescrewbecomesfilled,itforcesthescrewback,trippingalimitswitchthatactivatesahydrauliccylinderthatforcesthescrewforwardandinjectsthefluidplasticintotheclosedm
8、old③.Anantiflowbackvalvepreventsplasticunderpressurefromescapingbackintothescrewflights.Theclampingforcethatamachineiscapableofexertingispartofthesizedesignationandismeasuredintons.Arule-of-thumbcanbeusedtode
