专业模具英语.doc

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1、MoldConstruction1.Theinjectionmoldingandmachine1.1TheinjectionmoldingInjectionmoldingisprincipallyusedfortheproductionofthethermoplasticparts,althoughsomeprogresshasbeenmadeindevelopingamethodforinjectionmoldingsomethermosettingmaterials.Theproblemofinjectingameltedplasticintoamoldcavityfrom

2、areservoirofmeltedmaterialhasbeenextremelydifficulttosolveforthermosettingplasticswhichcureandhardenundersuchconditionswithinafewminutes.Theprincipleofinjectionmoldingisquitesimilartothatofdie-casting.Theprocessconsistsoffeedingaplasticcompoundinpowderedorgranularformfromahopperthroughmeteri

3、ngandmeltingstagesandtheninjectingitintoamold.Afterabriefcoolingperiod,themoldisopenedandthesolidifiedpartejected.Injection-moldingmachinescanbearrangedformanualoperation,automaticsingle-cycleoperation,andfullautomaticoperation.Theadvantageofinjectionmoldingare:(i)ahighmoldingspeedadaptedfor

4、massproductionispossible;(ii)thereisawidechoiceofmaterialsprovidingavarietyofusefulproperties;(iii)itispossibletomoldthreads,undercuts,sideholes,andlargethinsections.1.2Theinjection-moldingmachineSeveralmethodsareusedtoforceorinjectthemeltedplasticintothemold.Themostcommonlyusedsysteminthela

5、rgermachinesisthein-linereciprocatingscrew.Thescrewactsasacombinationinjectionandplasticizingunit.Astheplasticisfedtotherotatingscrew,itpassesthroughthreezones:feed,compression,andmetering.Afterthefeedzone,thescrew-flightdepthisgraduallyreduced,forcingtheplastictocompress.Theworkisconvertedt

6、oheatbyshearingtheplastic,makingitasemifluidmass.Inthemeteringzone,additionalheatisappliedbyconductionfromthebarrelsurface.Asthechamberinfrontofthescrewbecomesfilled,itforcesthescrewback,trippingalimitswitchthatactivatesahydrauliccylinderthatforcesthescrewforwardandinjectsthefluidplasticinto

7、theclosedmold.Anantiflowbackvalvepreventsplasticunderpressurefromescapingbackintothescrewflights.Theclampingforcethatamachineiscapableofexertingispartofthesizedesignation.Theinjection-moldingmachine,thereciprocating-screwinjectionsystemandismeasure