Abstract: The cavity surface of a foam mold is sprayed with a paint which becomes integrally bonded to the outer surface of the foam molded part. The sprayed paint unavoidably overlaps the parting faces of the mold around the outer edges of the mold cavity. In order to avoid the necessity of trimming a paint flash from the molded part along a line corresponding to the parting line of the mold, after the cavity is spray painted and while the paint is still wet the line of intersection between the cavity and the parting faces of the mold is contacted with a member which interrupts the continuity of the paint film. This avoids the formation of the paint flash on the molded part.

Abstract: Thermoplastic granules mixed with a blowing agent are processed in a barrel unit which encloses a rotating screw which mixes, works and plasticizes the mixture so that at the leading end of the barrel it is in a molten condition suitable for extrusion or injection molding. The screw has two compression stages with an intermediate decompression stage therebetween. At a location corresponding to the decompression stage of the screw the barrel has a vent therein which permits the escape of moisture vapors and other unwanted volatiles in the mixture. At the vent zone the forward faces of the screw flights are undercut to minimize the discharge of mixture through the vent.

Abstract: A mold for forming plastic foam parts in which an injection-molded plastic member forms a molding surface of the foam molding cavity against which foam plastic is adapted to be molded. The plastic member is preferably injection molded in a metal molding die from either polyethylene or polypropylene so that its molding surface is the reverse of the exterior surface of the plastic part to be foam molded therein. Vent passages and sealing beads may be integrally formed with the injection-molded member.