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1、Unit6InjectionMoldingInjectionmolding喷射造型法(Fig.6.1)isthepredominantprocessforfabricationofthermoplastics热塑性塑料intofinishedforms,andisincreasinglybeingusedforthermosettingplastics热固性塑料,fiber-filledcomposites,andelastomers人造橡胶.Itistheprocessofchoice精选的fortremendousvarietyofpartsra
2、nginginweightfrom5gto85kg.Itisestimatedthat25%ofallthermoplasticsareinjectionmolded.Ifnewermodifications,suchasreactioninjectionmolding真空成型,andthegreatlyincreasedrateofadoptionofplasticsassubstitutesformetalsareconsidered,itislikelythattheworldwideindustrialimportanceofinjectio
3、nmoldingwillcontinuetoincrease.Currently,probablyclosetohalfofallmajorprocessingunitsisinjectionmoldingmachines.In1988,adollarsaleofnewinjectionmoldingmachineryintheU.S.wasapproximately65%oftotalmajorpolymermachinerysalesvolume;thisincluded4,600injection-moldingunits.Themachine
4、sandtheirproductsareubiquitous到处存在的andaresynonymouswithplasticsformanypeople.Areciprocatingscrewinjection-moldingmachine往复螺杆式注塑机combinesthefunctionsofanextruderandacompressivemoldingpress.Ittakessolidgranulesofthermoplasticresin热塑树脂,meltsandpressurizesthemintheextrudersection,f
5、orcesthemeltathighvelocityandpressurethroughcarefullydesignedflowchannelsintoacooledmold,thenejectsthefinishedpart(s),andautomaticallyrecycles.Thismachineisadescendantoftheplungertype"stuffingmachine"patentedbytheHyattbrothersin1872tomoldcelluloid赛璐珞.In1575,theHyattsdevelopedth
6、efirstmulticavitymold,butitwasnotuntil1938thatQuillery(France)patentedamachineincorporatingascrewtoplasticizetheelastomerbeingmolded.----In1956,AnkerwerkNurembergcommercializedthemodem(modern?)reciprocatingscrewinjectionmoldingmachineforthermoplastics.Today,over50machinemanufac
7、turersarelistedinModernPlasticsEncyclopedia,offeringmachinestotheU.S.marketrangingfrom2to6,000tonsclampingcapacity.(Amachinewitha10,000-toncapacityhasbeenbuilttomold264-gallonHDPE(high-densitypolyethylene高密度聚乙烯)trashcontainers.)Ahostofsuppliersofauxiliaryequipment,molds,instrum
8、ents,andcontrolsservicethismajorsegmentofthepolymerind
