ABSTRACT
Punchingholesinsheetmetalisaveryoldandmatureprocess.Althoughnewand verysophisticatedmachines,controls,software,andtoolinghavebeendeveloped, especiallyinrecentyears,thebasicprocessofpunchingremainsthesame.Fundamentally,aholeismadeinsheetmetalmuchthesameaswithasimplepaper punch.Ineithercase,thereisapunchofdesiredshapeandmatchingdie.Around holeimpliesaroundpunchanddie,whereasasquareholewoulduseamatching punchanddiewithsquaregeometry.Atypicalpunchanddieassemblyisshown inFig.1.Theforcerequiredtopushthepunchthroughthematerialcomesfroma varietyofmeans,includingmanuallevers,andpneumatic,hydraulic,orelectrical sources.Ineverycase,theforcemustbesufficientto''shear''theuppersurface ofthematerialfollowedbya"breakthrough"or"fracture"completingthe holepunchingprocess.Inadditiontopunchingforce,typicallythesourceof powermustalsoovercomebuilt-intoolingmechanismssuchasstrippersprings. Theportionofmetalwhichisremovediscommonlycalledtheblankorslug. Thedistinctionbetweenthetwoisthatablankisusuallyaparttobeused,whereas aslugisconsideredscrap.Atypicalsheetmetalslugshowingthedistributionof shearandfractureisshowninFig.2.
