The operating principle of film blowing machine

Brief overview

    In the production process of blown film, the thickness uniformity of the film is a key indicator. And the longitudinal direction can be controlled by the stability of extrusion and drawing speed , and the lateral thickness uniformity of film generally depends on the die precision manufacturing, and changes according to the production process parameters. In order to improve the lateral thickness uniformity of the film, to introduce automatic transverse thickness control system, the common control methods include automatic die head (thermal expansion screws control) and automatic wind ring, it mainly introduces the principle and application of automatic wind ring here.

Fundamental principle

    The automatic wind ring structure adopts double draught style, and one of the down tuyere air volume remains constant, the circle of the up tuyere is divided into several air duct, each air duct is composed of air chamber, valve, motor, ect.The self-acting valve adjusts the air duct openness, controls the amount of each duct air volume.In the process of control, the thickness sensor transfer the signals of the film to the computer, the signal is compared with the current  average thickness by computer. It will use some operations thickness according to the amount of thickness deviation and curve variation tendencies ,to control the movement of the motor drive valve , when the film is thin, the motor positive shift, tuyere turns down; On the contrary, the motor counter movement, tuyere enlargement .To adjust the cooling speed of each point by  changing the amount of wind ring air volume , to make the film transverse direction thickness deviation in the range of targets.