Kev tswj cov lej (tseem siv computer lej tswj, thiab feem ntau hu ua CNC) yog kev tswj hwm ntawm cov cuab yeej siv tshuab (xws li kev xyaum, tshuab dhos, mills thiab 3D tshuab luam ntawv) los ntawm lub computer.Lub tshuab CNC ua cov khoom siv (hlau, yas, ntoo, ceramic, lossis cov khoom sib xyaw) kom ua tau raws li cov lus qhia tshwj xeeb los ntawm kev ua raws li cov lus qhia uas tau teev tseg thiab tsis muaj tus neeg siv phau ntawv ncaj qha tswj kev ua haujlwm.