How to choose the screw barrel length and diameter for cast film extrusion?

Selecting the appropriate screw barrel length and diameter for cast film extrusion is a complex and critical decision-making process that directly affects the efficiency, quality and cost of extrusion production.

The length and diameter of the screw barrel for cast film extrusion should be selected according to the characteristics of the extrusion material. Different extrusion materials, such as polyethylene, polypropylene, etc., have different viscosities, melt indexes and rheological properties, so it is necessary to select the appropriate screw barrel diameter based on these characteristics. Generally speaking, for materials with high viscosity and high melt index, a larger diameter screw barrel is usually required to improve the driving force and uniformity of extrusion; while for materials with low viscosity and low melt index, a smaller diameter screw barrel can be selected to reduce energy consumption and production costs.

Extrusion speed and output requirements are another important factor in selecting the length of the screw barrel. Generally speaking, a longer screw barrel can provide greater extrusion output and better extrusion uniformity, but it will also increase the energy consumption and operating cost of the equipment. High-output extrusion lines usually require longer screw barrels to increase the extrusion time and the mixing uniformity of the material in the barrel; while low-output extrusion lines can choose shorter screw barrels to reduce energy consumption and production costs.

The requirements of the extrusion process and the equipment configuration will also affect the choice of screw barrel length. Some extrusion processes may require specific mixing and dispersing functions, which usually require a longer screw barrel to ensure that the material is fully mixed and dispersed. In addition, the thermal stability and control of the equipment also need to be considered to ensure that the length and diameter of the screw barrel match the heating and cooling system of the equipment to ensure stable extrusion temperature and production quality.