A drive unit for operating a plastics injection machine includes a rotatably supported bushing intended for accommodation of an extruder screw and a rotor which includes a hollow shaft and is defined by an inner diameter sized to allow passage of the bushing and accommodated extruder screw through the rotor. The separator includes a separator body interposed between the rollers and having a pair of roller contact surfaces respectively opposing outer peripheral surfaces of the adjacent rollers, and a pair of arm portions which are guided by the guide grooves. The porous structure includes a multiplicity of ordered structural members defining the porous structure, the multiplicity of structural members intersecting to form structural member intersections, and a multiplicity of the pores defined by the multiplicity of structural members.