How to choose extrusion screens

Do you know how to choose a suited extrusion screens?

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.

Screens are often put in as a screen pack, with two, three or more screens of different meshes. Most packs have the coarsest screen up against the breaker plate to support the others, but putting it in "backward" also works, as the bigger particles get caught first and never reach the finest screen. The packs may be premade and put in baggies until needed, spot-welded together to ensure they stay in the right order or may have a crimped aluminum edge, which holds the screens together while serving as a gasket to prevent leakage.