Tsarin juyawa, wanda kuma aka sani da tsarin juyawa, tsarin juyawa, tsarin juyawa, da sauransu, hanya ce ta tsarin dumama mai zurfi. Hanyar ita ce a fara ƙara kayan filastik a cikin tsarin, sannan a ci gaba da juya tsarin a kan gatari biyu a tsaye sannan a dumama shi, sannan a shafa kayan filastik a hankali a narke su a manne su a cikin ramin tsarin a ƙarƙashin aikin nauyi da ƙarfin zafi. A saman duka, ana samar da shi zuwa siffar da ake so, sannan a sanyaya don samar da samfur.

(1) Ya dace da ƙera manyan sassa da kuma manyan sassa. Tunda tsarin ƙera juyawa yana buƙatar ƙarfin firam ɗin ne kawai don tallafawa nauyin kayan, mold, da firam ɗin kanta, da kuma ƙarfin rufewa don hana zubewar kayan, koda kuwa ana sarrafa manyan sassan filastik da manyan, babu buƙatar amfani da kayan aiki da molds masu nauyi sosai. Saboda haka, a ka'ida, kusan babu iyaka ga girman samfuran da aka yi ta hanyar ƙera juyawa.

(2) Ya dace da samar da samfuran filastik iri-iri da ƙananan rukuni-saboda sauƙin tsari da ƙarancin farashin mold don ƙera ƙera mai juyawa, yana da matukar dacewa don canza kayayyaki.

(3) Ya dace da sarrafa manyan kayayyaki masu ramuka masu siffofi masu rikitarwa, waɗanda ba za a iya kwatanta su da sauran hanyoyin ƙera su ba;

(4) Yana da sauƙin canza launin kayayyakin filastik. Idan ana buƙatar canza launin samfurin, kawai sai a tsaftace mayafin gyaran.

(5) Babban rashin amfanin gyaran juyi shine: yawan amfani da makamashi, domin a kowace zagayen gyaran juyi, gyaran juyi da tushen gyaran juyi suna buƙatar yin dumama da sanyaya akai-akai; zagayowar gyaran juyi yana da tsawo, saboda zafi galibi ana gudanar da shi ne ta hanyar filastik mai tsauri, don haka lokacin dumama juyawar gyaran juyi yana da tsawo; ƙarfin aiki yana da girma, kuma daidaiton girman samfurin ba shi da kyau.