Transcription of MODULE 5 SHEET METAL OPERATIONS
1 MODULE 5 SHEET METAL OPERATIONSSHEET METALWORKING Cuttingandformingthinsheetsofmetalusuall yperformedascoldworking Sheetmetal= (1/64)to6mm(1/4in)thick Platestock>6mmthick Advantage-Highstrength,gooddimensionalac curacy,goodsurfacefinish,economicalmassp roduction(lowcost). Cutting, bending ,drawingPARTSMADEBYSHEETM ETALFORMING Carbodies Aircraftfuselages Trailers Officefurnitureappliances Fueltanks CookwareSheet Metalworking Terminology Punch-and-die Toolingto perform cutting, bending , and drawing Stamping press Machine tool that performs most SHEET METAL OPERATIONS Stampings Sheetmetal productsA set of die and punch Press working of SHEET metalSHEET METAL OPERATIONS SHEARING BLANKING PUNCHING (PIERCING) bending STAMPING DRAWING DEEP DRAWING EMBOSSING SPINNING ROLL FORMINGSHEET METAL CHARACTERISTICSC haracteristics of metals important in SHEET point of sheared condition of sheetCrystallographic anisotropyMechanical fiberingCuttingOperation Shearing-usingamachinecalledpowershearor squareshear.
2 Blanking shearingaclosedoutline(desiredpartcalled blank) Punching shearedpartisslag(orscrap)andremainingst ockisadesiredpartCUTTING OPERATIONSHEARINGA nalysisClearance-4-8%butsometime1%ofthic knessToosmall GetpinchedandcauseanexcessiveburrClearan ce:c=a*tMetalgroupa 1100 Sand5052 Saluminumalloys, ; brass,softcoldrolledsteel, Coldrolledsteel,halfhard;stainlesssteel, Shapeandmaterialofthepunch Die,speedofpunching,lubrication Clearancebetweenpunch&dieDie,blankandpun chsize Foraroundblank,Blankpunchdiameter=Db-2cB lankdiediameter=Db Foraroundhole,Holepunchdiameter=DhHoledi ediameter=Dh+2c Cuttingforces:F=S t L= TS t LwhereS=Shearstrengtht=thicknessL=length ofcuttingedgeTS=UltimatetensilestrengthS TAGES IN SHEARING OF PUNCHED HOLEFEATURES OF SLUGB lanking punch and dieOther Cutting OperationsLANCING OPERATIONM aximumforce,Prequiredtobeexertedbythepun chtoshearoutablankfromthesheetcanbeestim atedasP= t SheetthicknessL Totallengthsheared -ShearstrengthofthesheetmaterialShearing force,SF= ShearingforceinKNL Lengthofcutinmmt ThicknessofmaterialinmmClearance between die and punch,c = PROGRESSIVE AND COMPOUND DIESPROGRESSIVE DIECOMPOUND DIEF orming-LimitDiagramAgridpatternofcircles , , , OperationsInV- bending , , , bending OPERATIONS Flanging Hemming Seaming Curling Channel, U- bending Air bending , Offset bending , Corrugating and Tube formingBENDING ,themetalontheinnersideoftheneutralplane iscompressed.
3 Drawing operation a cup-shape partDetail Steps of DrawingDetail Steps of Steps of Drawing Operation Redrawing Drawing without a BlankholderDefects in drawing Wrinkling in the flange Wrinkling in the wall Tearing Earing Anistropyin SHEET METAL Surface scratch ,itwillberetainedincupwallregion. Tearing:Itisacrackinthecup,nearthebase, ( R),andearheightandangularpositioncorrela tewellwiththeangularvariationofR. Surfacescratches:Usageofroughpunch, forming is held by jaws or drawbeadsat both the ends and then stretched by punch, such that the SHEET is stressed above yield strength. Whenthetensionisreleased, forming METAL SPINNINGM etalSpinningprocessisacoldformingprocess inwhichtheblankmetalappearstoflowsomewha tlikeapieceofclayonapotter' OF METAL SPINNINGE xternalshapeofthemandrelcorrespondstothe internalcontouroftheparttobeproduced. Theblankisclampedbetweenspinningmandrela ndafolloweronthetailstockspindle. Themandrel,blank, IN SPINNING PROCESSStep1:MetalForming Thisstepinvolvesthelayingdownofthemateri alontothemandrel.
4 Itisaccomplishedwithshortinsidetooutside moves. Materialgetseasiertoformasthepartisclose rtocompletionStep2 :Finishing FinishingisdoneatveryhighRPMs(1200+)soth ataminimumofforceneedbeappliedandverysmo othstrokescanbeused. SpinningTUBE SPINNING Thicknessofcylindricalpartsarereducedbys pinningthemonacylindricalmandrelrollers Partscanbespunineitherdirection Largetensileelongationupto2000% WITH OTHER FORMING PROCESSES Lowtoolingcostcomparedtootherformingtech niques. Conventionalspinningalsowastesaconsidera blysmalleramountofmaterialthanothermetho ds. Thestandardmethodofpressformingthepartre quiresmanysteps, forming Inbendingandembossingofsheetmetal,thefem aledieisreplacedwithrubberpad Rubberpadforming(RPF)isametalworkingproc esswheresheetmetalispressedbetweenadiean darubberblock,madeofpolyurethane. Underpressure,therubberandsheetmetalared rivenintothedieandconformtoitsshape, , ,theycanbemachinedintheshapeofdieorpunch .
