Lub pwm pwm yog ib yam cuab yeej tshwj xeeb uas siv rau hauv kev tsim khoom kom ua tau zoo hauv kev tsim cov khoom loj nrog kev ua haujlwm raug. Nws feem ntau siv rau hauv kev lag luam xws li tsheb, khoom siv hluav taws xob, thiab khoom siv hauv tsev. Lub pwm muaj ntau qhov chaw lossis theem uas cov hlau lossis lwm yam khoom siv hla dhau. Ntawm txhua qhov chaw, ib qho kev ua haujlwm tshwj xeeb raug ua, xws li txiav, khoov, lossis tsim. Thaum cov khoom siv nce mus txog lub pwm, nws dhau los ntawm ntau qhov kev hloov pauv me me, thaum kawg ua rau ib feem tiav. Cov pwm pwm uas hloov pauv tau sai thiab pheej yig yog cov uas paub zoo txog lawv qhov ceev thiab kev siv nyiaj tsawg, vim lawv tsis tas yuav teeb tsa ntau yam lossis hloov cov cuab yeej, txo lub sijhawm tsim khoom thiab cov nqi zog ua haujlwm. Lawv zoo tagnrho rau kev tsim cov khoom uas muaj cov qauv geometries nyuaj thiab kev kam rau siab. Tsis tas li ntawd, cov pwm pwm uas hloov pauv tau sai tuaj yeem suav nrog cov yam ntxwv xws li tho qhov, coining, thiab embossing hauv ib qho kev khiav, ua rau lawv muaj ntau yam siv tau.
Cov pwm ua kom zoo yog ib qho tseem ceeb hauv cov txheej txheem tsim khoom niaj hnub, ua kom yooj yim rau kev tsim khoom thiab xyuas kom meej tias kev tsim khoom ntau yam khoom thiab cov khoom sib xws tau zoo thiab sib xws.