A cikin sarrafa karafa da sarrafa kayan, simintin gyare-gyare ita ce babbar dabara don tsara karafa da gami zuwa sifofin da ake so. Daga cikin hanyoyin simintin gyare-gyare daban-daban, fitattun fasahohin fasaha guda biyu sun haɗa da injinan simintin gyaran kafa da injin ci gaba da yin simintin. Ko da yake manufar duka biyun ita ce canza narkakkar karfe zuwa tsayayyen tsari, suna aiki akan ka'idoji daban-daban kuma sun dace da aikace-aikace daban-daban. Wannan labarin yana yin nazari mai zurfi kan bambance-bambancen da ke tsakanin waɗannan hanyoyin simintin gyare-gyare guda biyu, yana bincika hanyoyin su, fa'idodi, rashin amfani, da aikace-aikace.