999久久久免费精品播放,色欲天堂在线观看,办公室激情娇喘嗯啊老师 ,99久久久久久久免费A片观看

The color of plastic material laser marking is yellow, which mainly depends on the material itself, the model used and the adjusted parameters, such as PVC plastic, the color of carbon dioxide laser marking is yellow, oxidized or vaporized; if it is marked with fiber laser, it is black; In addition, because of the material itself, the parameters of the laser marking machine are not adjusted correctly, which will cause the printing to become yellow.