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l )csign ior l \ l :urufacturcl )es ign or ( ' i rs t ing

( ' ; r s t i n g s o l r c o l l l t c n r o s l u r t t r l r t l l h c r r r ; r r r r r l t r t l u r i r r gr o e c s s c s .l i l r v o l r c sp o r r r i r r q ri n j c c t i n g r o l l c n n c l : t l n l o : t t t t o r r l r lt t r t l l r c r r : r l l o n , i n gt t o s o l i r l i l y A l l h o u g hu l r n o s t ; r n ysh: tpc h; r t i s t l cs ig l rc t l t t r t l ' bc t ' ; t s l . hc t l cs ig t rc r o r dcs ign l i r r l ru tnu l ; re t r r r .cc ; t tn ) r t rus lt :ons idcr nrny l : rc lo rsbc lorc dcc i r l i ng )n thc t ru tnr t fhc lu t ' i ngr r tccss o hc r rscd.Manyr l i l ' f i ' r cn l as t ing roccsscs rc r r ' : r i l : rb lc : r r r r lo t rshou lda l rcadybc la l r r i l i a r i lh thcsc i l ' no lscc hc re f ' c rcnccsl lhc c l t r l t l ' l hcsc c t ' l tu ' c o lcs . lhc l i r l l o rv ing ex t inc l r rdcs ce l ions n.rvhcn lo ttsc t ' ; rs l ing. hc :tr l r ' :ul l lgcsanrl t l is l t lv lnl i tg,csof sotttc ol ' lhc proccsscs,artdcxrmplcso l 'dcs igngu i t l c l i r rcs

W h e n ' I ' o I l se ' a s l i r r gl ) Whcn lhc pro t l r rc l c r l r r i t cd as i t ruchcavyscc l ions l ' complc r shapc .a pr ( )ccss uchassandcasl ingnray tc ntorccl l ic icnt than ahricat ion nd machining2) When usi l tg, t talcr ialshal arc rl i l l icrr l l o rnachinc, g, rcl iaclory nratcrials. asl i rrs o f inetolcranccs sing nvcslnrcnl asl inqmay rc an al l ract ivcsolul iorr-3) When largc producl iort c;rranti l ics t 'snral l to nrcdiunr sized corrrpler conrponcntsarerequired n zinr:or alurtt iniunr lkrys. hcn pressurc ie castinl l s of lcn appropriate4) When thc desired onrponcnlhns a complcx structurc.possiblywith rccntranl anglesanrlinlernalcavit ics. hcn casl ingcould bc lhc only lct:hrr iquc ossiblc5) When vibrat ioncl ' lbcls ave o bc ahsorhed . g the danrping f-machine ools to decreasethe eflbcts of 'mcchanical i l l ral ion and noisc. then san d castingol 'conrponerrts n grey castiron is often carrictl ou l6) When it is necessaryo prodrrcc tcnrs.suchas machincpcdestals nd baseplatcs. n whichmasses f mctalhavc o bc placcdstratcgical ly. asl ing s usual lyprcl-crahlco fabricat ion7) When singlc lcrnsarc reqrri rcd ;urckly.as in thc casc of protolypes thcn lhc abi l i ty toproducea pattern apidly.as i rr eranrplc n the l i r l l rnouldproccss, rakes astingattracl ive8) When dircc: l ional l rcngthproperl icsare nol dcsired n thc l inishcdcornponents9) When valuablcor precior.rsnclals are lo bc used. casting l l rovidcs a lcclrnir;uc l ratminirnises astagel0) Whcn it is possiblc o r lcsignor rcrlcsign hc producl in such a nranncr hat conrponcrrtsthat were original ly eparate anhe intcqrated nto one uni l

Advrn tages And l ) i sadvan lagcs ) f Some ( 'as t ing l ) rocessesSund ( 'us t inN. ' I ' h t ' r tdvar r t : lgcs;uc . a l l r ros t rny rnc l ; r l an hc usc t l . hc rc is v i f lu : t l l yno l i rn i lon thc s iz .c nd rvc igh t f ' p roduet , igh ro lnp lc r i ty i s poss ib lc ,oo l ing cos ls t rc or r ' ,and hcroule is dircct l ioln patlcr-no nrould. l 'hc disadvantagcs rc th;rtsolnc rnachuti l rg s usrral lynecessary, url i tcc f inrslr is poor, i l is di l ' l ' icul t o rrchicv,:closc loleranccs,antl i t is t tolpract ical o cast ong thin sections.( 'entr i l i t l iul ( 'u.st ing. ' l 'hc atlvanl; lgcs: l rc.hc r:entr i tugal i rrce aci l i tatcseomplclc i l l ing ofthe mould. thc gasr:s lrd rnpuri l iesconccnlr l lc on thc inncr surf: lcc irr casy 'ctt t t lv i t l , : t t tr t t lso l id outersur tacc s oh la incd,and the nrou ld s rc la t i vc lys i rnp lc l ' hc rn l in d is tdvar r t i tgcs

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arc that the process s lirnitcd to symlnetricalprtxlucts,and that if ' alloys of separablecompuundsrc bcingcasl hc conrpountls ay nttl bc cvcnly listributcd.Shrll h,lurltlin.q. dvanlftgestrc a rapidproduction ate,a good grain structure, nda goodsurl'accinish rnd lccuracyhus ninimising inishingoperations.fhe disadvantagesre ha tcxpcnsivc atlcrns,quiprncnl,ntl esinbindcrarcrcquircd. nd hcrc s a l imit to thesizeof part halcln hc mldc.I:nl l l l tni ld ['n\'(tt Advarrlagcsrc.c\pcnsivc altcrns:r 'c ol rcquircd rtd aper r draftis ntl t nccessaryn thc pir l lcrnsincr: l docs not nced o bc withdrawn.A disadvantagehou,cvcrs tlrat nachinings trsually cccssaryo achicvc hc tlcsircd recisionndsurlacel ln sh.lnyt'.ttnttnt'usting. Advlntagcs rre hal componenls f' high dimcnsional ccuracy,cxccllentsurfacc inish. andcxtrcme nlricaey canbe prtxluccd n almostany metal,andagoorl siz.e ang,c s nvailablc liorn a f'ew g,rams o around 40 kilograms.The maindisadvantagcsf the proccss rc the high costsof thc mctal dics and the time consuminglnlnul i tclurc l' hc moulds.Il i t, 'usting. l 'hcadvanlagcsrc:high productionates, ighprccision, ighquali ty urfacefinishcs, igh ntegritycastings ith low porosityandgoodgrainstructure, nd he ability toprodue:complex hapcs ith thin walls. fhc disadvantagesre hc high costs.ol ' achinesantl tooling which mcan hathigh quantities nd production atesare necessarytt allow anadetlualcelurn n invcslnrenl.

Exrmples0f DesignGuidelinesll Druli und Purting t.int I'ttsilfurn. olh of theseelemenls re closely elated.Where heprocesss such hata pitttern r thecastproducthas o hc rcmovcd rom he mould n a linearmanncr, r a corc has o be removcd ntact, hcn rlraftwill benecessary. raft s lhe amountof taperon thepattern r mouldprovidcd o allow easy xtraction n sand asting xtractionof a plttcnrwith no draftwil l ctuse hc mould o tcarandcrumblc,n dic castingnadequatetlr l ft rnay ause ragmnrks n hc finishcd omponcnl ndcvcnprcvent omponentemoval.' l 'hccr tcrn ;r l ra f ia l rg lcs usual ly c lw 'ccn 5"and1". rv i th n lcmal la f iangles ouhlehisduc o thc act halon cot l l inghccasl ing hr inksowanl hccore. In invcstmcntast ingsrrul l trnounl ul ' drafi rs alsoncccssaryo al low \\' i t\ pal lcrns o bc rcmtrvediom thernoultl i l rglic t:xcept n cascs hcrc hcmould s dcstroycd n castingctnttval..g. hc ful llnould pr()ccss r irrvcslmclrt asl ing, hc mould ptrting l ine nrustbe carcf'ul ly hoscn.t.lsual lyhisshould e a flat, ather hanstcpped r contoured,lanc.' l 'heinc shorrld c atthc corncrs r edges f thecasl ing ather hanalong flal surt'aces.his retluceshevisibi l i tyof thc cxccssmaterit l that oftcn cscapes long hc line - i c . the l lash. l 'hcparting ineintlucnccshe fol lowing;caseof nurukl ing, ccuracy, fl lcicntgating. asl ingweight, henunrhcr r cores eccssary,nd he manner n which he cttrcswil l bc supported.igureshows xarnplcsf dra l iandpar t ingine mpl icat ions.2l l tql l ' l -hirkne.s.In ctstings:rs al l thickncsslccrc:rscsoproblcmsend o increasc. orcxamplcn sand astings alls ess han6mm hickcln cause roblcms,t rnay hereftrreechcaper()uscsl ightlymorenratcrial n thickcrw:l l ls hancausencrcascdcrap alesn thefiruntlry.' l 'hc trrthcr hc nrctalnrusl lorv in the ntoultl hc thickcr he scction ruslbe.Minirnumwall thicknesss ol 'coursc lcpcndcnt n the proces:;ndmalcrial. 'g. a 0.4mmwl l l th ickncssscasi ly hta inablcn smal l . inc iccast ings.

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3l ( lnihtr i t t i tv rt l l l l t t l t ' r ' i t t l l 'h i tknrtr fhc r lcsigncr sl t t tul t l t l lct l lpt lo crcate casl ings r l funi f i rrnr lval l thicl .ncss I 'his is bccarrsc l i rncnsionrr l nd trrct l r l l r trgic:r lhlngcs ()ccur lscoo l ing rnd so l i t l i l l ca l io l tl t kc p lu t ' c ant l rny loc r t l v r r i r t l i ons n thc ra lc t t wh ich thesechangcs ccurw i l l : r l ' l l ' c thc qua l i tyo l ' thc cas l ing . S incc hc spcc t l { ' l hechangcss rc la ledto lhe vo lurncof rnc la l t i s impor ' l l n l o kccp thc cross cc l i t tn ; t l rc i tcons lan l hroughot t l .[ :o r cxamplc l ' l par to f ' i l cas l inHr rs la rgcsur fhcc rca in rc la t ion o i ts vo lu tnc t rv i l l hcsub jcc lcd o rap id :oo l i r rg a lcs : rn t l u , i l l thc rc forcprohtb ly hc hard or h lvc a hard sk in{ 'onvcrscly thickcr sccl ionscool lnorc slorvly antl rnay thcrcftrrc trnlainshrinkagccavi l ics,porosi ly, or hf l r 'ca largc grain slrut ' l rr rc. nlcr ior rval lsand sccl i r lns . t t t l nrt l lc slrtn' ly l i l t t tcxtcrnrl sccl ions nd hcrcl i rrcshouldbc aboul20'Z' hinncr.4) Rilrrurul 4'ch:: -hcsctt 'c sctl o givc ncrcascdtrcngth ntt igidity othc rninimumadditionol ' wcight ' l -hcy shouldbe careful lydcsignedpossib i l i tyf 'hot po ls ,hr ink:rgcnddis lo t ' t ion.

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