Extrusion basics: How to choose screens

Allan Griff | Jul 16, 2015

Choosing appropriate screens for an extrusion process involves striking a balance between filtration needs (removing more contaminants) and overheating. Finer screens get more contaminants out, but they also raise back-pressure in the extruder, which requires more power from the motor and, thus, creates more frictional heat. Barrel cooling may help, but it isn't efficient because it raises viscosity on the barrel wall and makes the motor work even harder, putting back some of the heat taken out by the coolant. Finer screens also need to be changed more frequently.

Some useful tips:

Allan Griff is a veteran extrusion engineer. He started out in tech service for a major resin supplier, and has been working on his own now for many years as a consultant, expert witness in law cases, and especially as an educator via webinars and seminars, both public and in-house. Griff wrote the first practical extrusion book in the 1960s, as well as the Plastics Extrusion Operating Manual, which has been updated almost every year and is available in Spanish and French as well as English. You can find out more on his website, www.griffex.com, or via email at [email protected].

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