Extrusion machine types

Today, continuing with our article series about the extrusion process, we speak about the different classes of extruders.

There are two classes: piston extruders and screw extruders.

Piston extruders were the first extruders used with plastic materials. Also known as RAM extruders, they work by a hydraulic press which pushes the piston with the material into the die.

This method is used for specific materials like PTFE that can’t be extruded through conventional extruders.

Of the screw extruders, there are three types:

Single screw extruders are the most commonly used in plastics manufacturing, and these are the extruders that we use at SCT-Straw to make our products for the various industries we work in, such as automotive and food. His function consists of the screw that by pressure and heat pushes the plastic from the die at the exit of the tooling. This method is used for all kinds of products (tubes, windows, industrial profiles, etc.) or materials like PVC, PP, PE, PS, ABS, etc.

Double screw extruders are used in operations that require melting, mixing, removing gases, and performing reactions to create granules or shape profiles. Dual screw extruders can be co-rotating if the two screws rotate in the same direction, counterrotating if everyone rotates in different directions. The biggest problem with the double screw extruders is that the process can be very aggressive for the material, and depending on the speed of extrusion, the melt may not be entirely efficient, but in optimal conditions, this has more production capacity.

There are also multiscrew extruders, but these extruders are not common.

Thanks for reading the article; we hope to bring more after the holidays.