模(mo)(mo)(mo)(mo)具(ju)(ju)(ju)(ju)在(zai)使用(yong)(yong)(yong)過程中(zhong)，其零(ling)(ling)件(jian)(jian)(jian)會(hui)因(yin)磨(mo)(mo)損(sun)(sun)或損(sun)(sun)壞而失效(xiao)。如果(guo)磨(mo)(mo)損(sun)(sun)或損(sun)(sun)壞嚴重(zhong)，模(mo)(mo)(mo)(mo)具(ju)(ju)(ju)(ju)無(wu)法修復(fu)，模(mo)(mo)(mo)(mo)具(ju)(ju)(ju)(ju)就(jiu)應(ying)(ying)該報廢(fei)。如果(guo)模(mo)(mo)(mo)(mo)具(ju)(ju)(ju)(ju)的(de)(de)(de)零(ling)(ling)件(jian)(jian)(jian)是(shi)互(hu)換的(de)(de)(de)，零(ling)(ling)件(jian)(jian)(jian)失效(xiao)后可以更換，那(nei)么模(mo)(mo)(mo)(mo)具(ju)(ju)(ju)(ju)的(de)(de)(de)使用(yong)(yong)(yong)壽(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)理論上(shang)是(shi)無(wu)限的(de)(de)(de)。但是(shi)，模(mo)(mo)(mo)(mo)具(ju)(ju)(ju)(ju)長期(qi)(qi)使用(yong)(yong)(yong)后，零(ling)(ling)件(jian)(jian)(jian)趨于老化，故(gu)障概(gai)率大大增(zeng)加(jia)，維修成(cheng)本也(ye)隨之增(zeng)加(jia)。同時，模(mo)(mo)(mo)(mo)具(ju)(ju)(ju)(ju)往往需要(yao)維修，這(zhe)將(jiang)直接影響(xiang)零(ling)(ling)件(jian)(jian)(jian)的(de)(de)(de)生產(chan)。因(yin)此(ci)，當修復(fu)模(mo)(mo)(mo)(mo)具(ju)(ju)(ju)(ju)在(zai)經濟上(shang)不合(he)理時，也(ye)應(ying)(ying)考慮報廢(fei)。模(mo)(mo)(mo)(mo)具(ju)(ju)(ju)(ju)報廢(fei)前完(wan)成(cheng)的(de)(de)(de)工作循環次(ci)數或生產(chan)的(de)(de)(de)零(ling)(ling)件(jian)(jian)(jian)數稱(cheng)為模(mo)(mo)(mo)(mo)具(ju)(ju)(ju)(ju)的(de)(de)(de)總壽(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)。此(ci)外，還應(ying)(ying)考慮模(mo)(mo)(mo)(mo)具(ju)(ju)(ju)(ju)在(zai)兩次(ci)維修期(qi)(qi)間的(de)(de)(de)使用(yong)(yong)(yong)壽(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)，如沖模(mo)(mo)(mo)(mo)的(de)(de)(de)刃(ren)磨(mo)(mo)壽(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)。在(zai)設(she)計和制造模(mo)(mo)(mo)(mo)具(ju)(ju)(ju)(ju)時，作為用(yong)(yong)(yong)戶會(hui)對模(mo)(mo)(mo)(mo)具(ju)(ju)(ju)(ju)壽(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)提出要(yao)求，稱(cheng)為模(mo)(mo)(mo)(mo)具(ju)(ju)(ju)(ju)的(de)(de)(de)預期(qi)(qi)壽(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)。確定模(mo)(mo)(mo)(mo)具(ju)(ju)(ju)(ju)的(de)(de)(de)預期(qi)(qi)壽(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)應(ying)(ying)綜合(he)考慮兩個因(yin)素:一是(shi)技術上(shang)的(de)(de)(de)可能(neng)性，如沖模(mo)(mo)(mo)(mo)具(ju)(ju)(ju)(ju)的(de)(de)(de)刃(ren)磨(mo)(mo)壽(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)，即使生產(chan)壽(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)也(ye)應(ying)(ying)盡(jin)可能(neng)縮短；當模(mo)(mo)(mo)(mo)具(ju)(ju)(ju)(ju)的(de)(de)(de)使用(yong)(yong)(yong)壽(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)，即使在(zai)使用(yong)(yong)(yong)壽(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)，也(ye)應(ying)(ying)盡(jin)可能(neng)縮短模(mo)(mo)(mo)(mo)具(ju)(ju)(ju)(ju)的(de)(de)(de)使用(yong)(yong)(yong)壽(shou)(shou)(shou)命(ming)(ming)(ming)(ming)(ming)，也(ye)應(ying)(ying)盡(jin)可能(neng)縮短。
