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1、EML2322L–MAEDesignandManufacturingLaboratoryTypicalTolerancesofManufacturingProcessesInthepast,oneofthetraditionalweaknesseswithgraduatingmechanicaldesignengineersistheirinabilitytoselecttolerances.MoststudentswerereasonablyproficientusingoneormoreCADpackagesandcouldproducedrawingswhichwerepre
2、ttygood(giventheirlimitedexperiencelevels).However,despiteknowinghowtoputatoleranceonadrawing,moststudentsgenerallyhadnoideawhattheactualnumbersshouldbe,oranysenseofwhattheprocessforselectingreasonabletolerancesmightconsistof.SinceGeometricDimensioningandTolerancing(GD&T)isinwidespreaduseinind
3、ustry,theMAEcurriculumhaschangedtoincludeitinEML2023.Nevertheless,knowinghowtoproperlyexpressatoleranceforcylindricityorparallelismbetweentwosurfacesonapartdrawingisnotthesamethingasknowingwhatareasonablenumberforthattoleranceshouldbe.AftertakingEML2322L,thestudentsshouldbemuchmoreproficientin
4、theseareas.Tofacilitatethestudents’understandingofthisimportantareaofmechanicaldesign,wehaveputtogetherafewslidesonsomecommonmanufacturingprocesses,andwhattheirtoleranceproducingcapabilityis.AftertakingEML2322L,thestudentsshouldhaveatangibleunderstandingofthetolerancesassociatedwithbasicmanufa
5、cturingprocessesusedinthiscourse(i.e.milling,turning,drilling,reaming,bandsawcutting,etc.)ProcessTolerancesProcessTolerancevs.FeatureSizeSurfaceFinishvs.ProductionTimeFIGURE15.10.Surfacefinishproducedbyvariousprocesses.(Source:Wikipedia)Figure15.5presentsacollectionofthemostcommonmanufacturing
6、processesandthetolerancescommonlyassociatedwitheachofthem.Asexplainedinthelegend,theshadedportionsofthebarsrepresenttheaverageapplicationoftheseprocessesandmeanvirtuallyanymanufacturingshopshouldbeabletoachievethesetolerances.Theremainingportionofthebarindicatesthelessfrequentapplication,which
7、meansoneoftwothings:(1)highlyskilledoperatorsandequipmentinexcellentconditionarerequiredtoobtainthetolerancesonthehigherprecisionendoftherangeor(2)theprocesscaneasilyachievethetolerancesonthelowerprecisionendoftherange,butacheaperaltern
