Mainly by adjusting the ratio of foundation speed to traction speed, it can be calculated by simple mathematical formula. The mold can only fine-tune the uniformity of film thickness.

The mold is covered from top to bottom, that is, when it is thick, loosen the screw (the thick side is tightened hard). This is called a continuous die. If it is a big mouth at the bottom, the upper die head is put in, which means loose thin edge and tight thick edge. It's called anti-tune.