The smooth way to mold microcellular foam parts.

MuCell microcellular foam parts, which commonly have a dull surface and splay marks, can now be injection molded with smooth, glossy surfaces, thanks to a new method of thermally cycling molds from hot to cold with little or no cycle-time penalty. The process is also said to produce a smooth, resin-rich surface on non-foamed, glass-reinforced parts and helps eliminate flow and weld lines. These capabilities are attributed to the Rapid Heat Cycle Molding (RHCM) process developed by injection molder Ono Sangyo Co., Ltd. of Tokyo, Japan. The company is working with Trexel Inc., Woburn, Mass., developer and licensor of the MuCell microcellular foam process, to market the RHCM process worldwide.

The process works by outfitting the mold with both steam-heating and water-cooling channels. During injection, steam at 120 C (248 F) keeps the mold above the resin's heat-distortion temperature. During the holding phase, steam is halted and cooling water flows through the mold. Cycle-time penalty can be from zero to 5%, according to Toru Ueki, general manager of Ono Sangyo's Technical Div., R&D Section.

Trexel sources note that RHCM alone does not provide the benefits of the MuCell process. RHCM will not remove sink marks, which are all the more visible on smooth surfaces. Nor will RHCM alone improve the dimensional stability of parts.

Trexel will become the demonstration center for RHCM in North America and Europe, while Ono Sangyo will be the demonstration center for Asia, as well as the worldwide licensor. The process has been in use for four years and six molders are now practicing it. Kyowa Industrial Co. Ltd. of Niigata, Japan, has worked with Ono Sangyo to build molds for the process. It has a plant in Wheeling, Ill., and a new one will open early next year in Tijuana, Mexico. Trexel: [phone]/PTDirect: 262XD * Kyowa USA: [phone]/www.kyowa-ind.co.jp

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