A plasticating screw including a grating mixing section provided to enhance mixing of incompatible materials. The screw includes a mixing section including an inlet groove having a closed distal end, a discharge groove circumferentially spaced from the inlet groove, the discharge groove having a closed proximal end. Located between the inlet groove and the discharge groove is a land region is including at least one grating element that includes a plurality of grooves extending between the inlet groove and the discharge groove.