Nyob rau hauv hnyav welding, ib qho hnyav yog siv uas tuaj yeem yaj cov polymer ib ntus ntawm chav tsev kub. Thaum qhov no tshwm sim, cov saw hlau polymer yog pub dawb txav mus rau hauv cov kua thiab tuaj yeem sib xyaw nrog lwm cov chains zoo sib xws hauv lwm cov khoom. Muab sijhawm txaus, cov kuab tshuaj yuav nkag mus rau hauv cov polymer thiab tawm mus rau ib puag ncig, kom cov chains poob lawv txoj kev mus. Qhov no tawm ntawm cov khoom loj ntawm cov khoom sib txuas ntawm cov khoom siv polymer uas ua rau cov khoom hnyav.
Cov txheej txheem no feem ntau yog siv los txuas PVC thiab ABS yeeb nkab, xws li cov kav dej hauv tsev. Cov "gluing" ua ke ntawm cov yas (polycarbonate, polystyrene lossis ABS) qauv kuj yog cov txheej txheem vuam hnyav.
