a screw for a plasticating apparatus has one or more helical flights . a portion of the screw has a plurality of advancing grooves arranged in a noncontinuous helix cut in the screw . the advancing grooves are dimensioned to receive material therein as the material is conveyed through the barrel . the screw has a plurality of noncontinuous cross - cut grooves traversing one or more of the advancing grooves . the cross - cut grooves have a second helix angle greater than the first helix angle and less than ninety degrees ; and / or one or more of the cross - cut grooves have a third helix angle of about ninety degrees .