Umusumari wa sima, uzwi cyane nk'umusumari w'icyuma, ni ubwoko bw'imisumari, ukoresheje ibyuma bya karubone,
ibikoresho ni ibyuma 45 cyangwa ibyuma 60, nyuma yo gushushanya insinga, annealing, gukora imisumari, kuzimya nibindi
inzira, kubwibyo rero biragoye.Igikorwa cyayo ni ugutera imisumari mubindi bigoye cyane imisumari