Cylinder for a twin-screw extruder with a helical channel of varying depth

A cylinder assembly for a twin-screw extruder, comprising a cylinder having a variable wall thickness defining an extrusion space for receiving twin screws of the twin-screw extruder and a hollow-cylinder mantle surrounding the cylinder, wherein at least one channel having a helical shape and a cycle depth is formed on an outer side of the cylinder by a winding vortex process and an inlet and outlet are formed in the hollow-cylinder mantle in communication with the at least one channel for allowing a flow of a tempering medium from the inlet to the outlet via the at least one channel, the hollow-cylinder mantle closing the at least one channel, and wherein the cycle depth of the at least one channel varies along the circumferential direction of the cylinder such that the cycle depth is largest in regions where the wall thickness of the cylinder is largest and the cycle depth is smallest in regions where the wall thickness of the cylinder is smallest.