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The operation of a job electroforming shop that specializes in molds for making vinyl rotational or slush cast items for automotive trim is described. This activity has increased to considerable proportions in the past five years because the automotive industry has accepted the many advantages of vinyl plastics for trim. Electroformed molds for the production of vinyl plastisol articles are not new, having been used for a number of years in the production of dolls and toys, both of which are large and high-production businesses. The Sun Rubber Co. in Barberton, Ohio, a large maker of vinyl toys, is believed to be the first to propose a vinylskinned arm rest with good leather grain for the 1955 Ford. For various reasons, the Sun Co. did not push the project, but the idea was launched and others continued the work. Today nearly all automobiles have vinyl plastisol skins filled with urethane foam for arm rests and other items. Figures 1 and 2 show some typical auto items. Although electroformed metal molds are most generally used, other molds are suitable, including: 1. Cast aluminum molds—the cheapest and fastest to make, as they can be cast from low-cost patterns, and the molds themselves are not expensive. They have been used to some extent for vinyl trim. Disdavantages noted are porosity, resulting in poor surface finish or blow holes, and imperfect detail reproduction, limiting its use for leather grain items. There are also some size problems due to shrinkage. These molds do not have as high heat transfer as copper-nickel-plated molds, so production cycles are longer. Finally, the surface is softer and will not wear as long as electroformed nickel. 2. Shaw precision process cast molds —have distinctly better detail and surface finish, but still cannot copy leather grain as perfectly as the electroforming method. 3. Metal sprayed molds—have fairly good surface detail and are cheaply and quickly made. Their disadvantages are considerable: porosity, resulting in blistering; poor wear (usually sprayed tin and alloys); and low strength.
Ritzenthaler, Phil J.
President, Plating Engineering Co., Milwaukee, Wisc.