an apparatus for molding of plastic products in which a softened plastic material is extruded from an extruder in the shape of belts or rods , the extruded material is introduced onto a main molding roll having an outer surface with a contour of the piece to be molded and the plastic material is formed into a shape corresponding to the outer surface of the main molding roll by utilizing the fluidity of the plastic material , followed by rapid cooling , to produce a plastic product having a curved shape .