May 30, 2022
How the blow molding machine works
In the production process of blown film, the film thickness uniformity is a key indicator. The longitudinal thickness uniformity can be controlled by the stability of extrusion and traction speed, while the transverse thickness uniformity of the film generally depends on the precision manufacturing of the die. , and changes with the production process parameters. In order to improve the lateral thickness uniformity of the film, an automatic lateral thickness control system must be introduced. Common control methods include automatic die head (thermal expansion screw control) and automatic air ring. Here we mainly introduce the automatic air ring. Principles and Applications.
The structure of the automatic air ring adopts the double air outlet method, in which the air volume of the lower air outlet is kept constant, and the upper air outlet is divided into several air ducts on the circumference. degree to control the air volume of each air duct.
During the control process, the film thickness signal detected by the thickness measuring probe is transmitted to the computer, and the computer compares the thickness signal with the current set average thickness, performs calculations according to the thickness deviation and the curve change trend, and controls the motor to drive the valve to move. When the film is thin, the motor moves forward and the air outlet is closed; on the contrary, the motor moves in the reverse direction and the air outlet increases. By changing the air volume of each point on the circumference of the air ring, the cooling speed of each point is adjusted, so that the lateral thickness deviation of the film is controlled within the target range. .