Barrel and Screw Component Drilling for Extruders
Extruder barrels are heavy-walled tubes that contain the rotating screw. The barrel needs a precision bore for the screw to rotate with minimal clearance. Some barrels also have drilled heating or cooling channels along the length. I have worked on extruder barrels for everything from pelletizing lines to blown-film systems, and the tolerance demands are consistently tighter than what you see in general hydraulic cylinder work. The barrel is typically 1-5 meters long with a 50-200mm bore. The material is usually nitrided steel (like 38CrMoAl or 31CrMoV9) or bimetallic for wear resistance. The bore tolerance is typically +0.05mm and the surface finish is Ra 0.4um or better — and I have seen specs as tight as Ra 0.2um for high-wear applications like glass-filled nylon extrusion. ...