1ShiouFJ,ChenCH(2003)Determinationofoptimalball-burnishingparametersforplasticinjectionmoldingsteel.IntJAdvManufTechnoChao-ChangA.ChenWen-TuLBasedontheinjectionmoldsteelgrindingandpolishingprocessesautomatedsurfacetreatment1IntroductionPlasticsareimportantengineeringmaterialsduetotheirspecificcharacteristics,suchascorrosionresistance,resistancetochemicals,lowdensity,andeaseofmanufacture,andhaveincreasinglyreplacedmetalliccomponentsinindustrialapplications.Injectionmoldingisoneoftheimportantformingprocessesforplasticproducts.Thesurfacefinishqualityoftheplasticinjectionmoldisanessentialrequirementduetoitsdirecteffectsontheappearanceoftheplasticproduct.Finishingprocessessuchasgrinding,polishingandlappingarecommonlyusedtoimprovethesurfacefinish.Themountedgrindingtools(wheels)havebeenwidelyusedinconventionalmoldanddiefinishingindustries.The2geometricmodelofmountedgrindingtoolsforautomatedsurfacefinishingprocesseswasintroducedin.Afinishingprocessmodeofsphericalgrindingtoolsforautomatedsurfacefinishingsystemswasdevelopedin.Grindingspeed,depthofcut,feedrate,andwheelpropertiessuchasabrasivematerialandabrasivegrainsize,arethedominantparametersforthesphericalgrindingprocess,asshowninFig.1.Theoptimalsphericalgrindingparametersfortheinjectionmoldsteelhavenotyetbeeninvestigatedbasedintheliterature.Fig.1.SchematicdiagramofthesphericalgrindingprocessInrecentyears,someresearchhasbeencarriedoutindeterminingtheoptimalparametersoftheballburnishingprocess(Fig.2).Forinstance,ithasbeenfoundthatplasticdeformationontheworkpiecesurfacecanbereducedbyusingatungstencarbideballoraroller,thusimprovingthesurfaceroughness,surfacehardness,andfatigueresistance.Theburnishingprocessisaccomplishedbymachiningcentersandlathes.Themainburnishingparametershavingsignificanteffectsonthesurface3roughnessareballorrollermaterial,burnishingforce,feedrate,burnishingspeed,lubrication,andnumberofburnishingpasses,amongothers.TheoptimalsurfaceburnishingparametersfortheplasticinjectionmoldsteelPDS5wereacombinationofgreaselubricant,thetungstencarbideball,aburnishingspeedof200mm/min,aburnishingforceof300N,andafeedof40m.Thedepthofpenetrationoftheburnishedsurfaceusingtheoptimalballburnishingparameterswasabout2.5microns.Theimprovementofthesurfaceroughnessthroughburnishingprocessgenerallyrangedbetween40%and90%.Fig.2.Schematicdiagramoftheball-burnishingprocessTheaimofthisstudywastodevelopsphericalgrindingandballburnishingsurfacefinishprocessesofafreeformsurfaceplasticinjectionmoldonamachiningcenter.TheflowchartofautomatedsurfacefinishusingsphericalgrindingandballburnishingprocessesisshowninFig.3.Webeganbydesigningandmanufacturingthesphericalgrindingtoolanditsalignmentdeviceforuseonamachiningcenter.TheoptimalsurfacesphericalgrindingparametersweredeterminedbyutilizingaTaguchisorthogonalarraymethod.FourfactorsandthreecorrespondinglevelswerethenchosenfortheTaguchisL184matrixexperiment.Theoptimalmountedsphericalgrindingparametersforsurfacegrindingwerethenappliedtothesurfacefinishofafreeformsurfacecarrier.Toimprovethesurfaceroughness,thegroundsurfacewasfurtherburnished,usingtheoptimalballburnishingparameters.Fig.3.Flowchartofautomate