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1、Lesson20RapidprototypingTextRapidprototypingistheautomaticconstructionofphysicalobjectsusingsolidfreeformfabrication.Thefirsttechniquesforrapidprototypingbecameavailableinthelate1980sandwereusedtoproducemodelsandprototypeparts.Today,theyareusedforamuchwi
2、derrangeofapplicationsandareevenusedtomanufactureproductionqualitypartsinrelativelysmallnumbers.Somesculptorsusethetechnologytoproducecomplexshapesforfineartsexhibitions.RapidPrototyping(RP)iscurrentlythemostadvancedmethodforquicklycreatingaprototype.Thi
3、sisachievedbyusingaRapidPrototypingmachine.RapidPrototypingmachinescanproduceprototypesinaveryshorttime.Dependingonthecomplexityoftheprototype,itmaytakeanywherefromamatterofhourstoafewdaysforitscompletion.Rapidprototypingisalsocommonlycalledsolidfree-for
4、mfabrication,layeredmanufacturing,orcomputerautomatedmanufacturing.Fig10.1RapidPrototypingmachineandpartRapidprototypingtakesvirtualdesignsfromcomputeraideddesign(CAD)oranimationmodelingsoftware,transformsthemintothin,virtual,horizontalcross-sectionsandt
5、hencreateseachcross-sectioninphysicalspace,oneafterthenextuntilthemodelisfinished.ItisaWYSIWYGprocesswherethevirtualmodelandthephysicalmodelcorrespondalmostidentically.Withadditivefabrication,themachinereadsindatafromaCADdrawingandlaysdownsuccessivelayer
6、sofliquid,powder,orsheetmaterial,andinthiswaybuildsupthemodelfromaseriesofcrosssections.Theselayers,whichcorrespondtothevirtualcrosssectionfromtheCADmodel,arejoinedtogetherorfusedautomaticallytocreatethefinalshape.Theprimaryadvantagetoadditivefabrication
7、isitsabilitytocreatealmostanyshapeorgeometricfeature.Theword"rapid"isrelative:constructionofamodelwithcontemporarymethodscantakefromseveralhourstoseveraldays,dependingonthemethodusedandthesizeandcomplexityofthemodel.Additivesystemsforrapidprototypingcant
8、ypicallyproducemodelsinafewhours,althoughitcanvarywidelydependingonthetypeofmachinebeingusedandthesizeandnumberofmodelsbeingproducedsimultaneously.Somesolidfreeformfabricationtechniquesusetwomaterialsinthecourseofconstruct