Blow molding machine mold

In the production process of blown film, the uniformity of film thickness is a crucial indicator. The longitudinal uniformity of film thickness can be controlled by the stability of extrusion and traction speed, while the transverse uniformity of film thickness generally depends on the precision manufacturing of the die head and changes with the production process parameters. In order to improve the transverse uniformity of film thickness, an automatic transverse thickness control system must be introduced. Common control methods include automatic die head (thermal expansion screw control) and automatic air ring. This article mainly introduces the principle and application of automatic air ring.

Basic principles

Fully automatic blow molding machineThe automatic air ring structure adopts a dual air outlet method, where the air volume at the lower air outlet remains constant, and the upper air outlet is divided into several air ducts on the circumference. Each air duct is composed of an air chamber, a valve, a motor, etc. The motor drives the valve to adjust the opening degree of the air duct and control the air volume of each air duct.

During the control process, the thickness probe detects the thickness signal of the thin film and transmits it to the computer. The computer compares the thickness signal with the current set average thickness and performs calculations based on the thickness deviation and curve trend. It controls the motor to drive the valve to move. When the thin film is too thin, the motor moves forward and the air outlet closes; On the contrary, the motor moves in the opposite direction, and the air outlet increases. By changing the air volume at each point on the circumference of the air ring and adjusting the cooling speed at each point, the lateral thickness deviation of the film is controlled within the target range.