Process for the production of plastic material parts by controlled molding-thermoforming

Abstract

A process for the production of a plastic material part with a wear-resistant surface, having a predetermined nonplanar shape, comprising heating a blank of plastic material on a first side thereof opposite a second side on which it is desired to produce the wear-resistant surface, to adjacent the melting temperature of the plastic material, such that the temperature of the second side is substantially lower than the temperature of the first side. The blank thus heated on only the first side is introduced into a mold cavity, and is subjected to elevated pressure in the mold cavity with a surface of the mold cavity in contact with the second surface of the blank having a nonplanar shape complementary to the desired predetermined nonplanar shape of the second surface, thereby to impart to the second surface that predetermined shape while the second surface is at that substantially lower temperature. The surface of the mold cavity is produced either by extending a punch into the mold cavity in contact with the blank, or else the surface of the mold cavity is stationary and the blank is pressed into contact with the stationary surface of the mold cavity by pressure of a liquid, or both. The blank is of high molecular weight polyethylene having molecular chains oriented parallel to the second surface at least adjacent the second surface. The formed blank is for example an osteo implant such as a cotyle.

Dependencies are inferred from the claim text.