Caij nplooj ntoos hlav pwm, cov khoom nyob rau hauv pwm tom qab nias, yuav ua li cas tshem tawm cov khoom?

(1) Yuav tsum muaj lub tshuab demolding
(2) Muaj cov cuab yeej kho pwm
(3) Tshem tawm cov khoom nrog lub tog raj kheej
(4) Nrog lub tog raj kheej tswj valve