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SEATTLE, WA- March 5, 2005 - Jobwerx News -
Conventional single-face, multi-component molds typically inject one material into the cavities on half of the mold face and the second material into the other half. Between cycles, the rotary platen flips the mold on a horizontal axis. Stack molds multiply the number of usable mold faces and also permit molding the entire mold face with each material. The new designs have a center platen that rotates on a vertical axis. Depending on the system, the center component can have either two or four faces and rotate 90° or 180° each time the mold opens.

Gram Technology, a Danish company, offers a unique process for stack-molding concept called Spin Stack Technology that delivers faster cycle times, less part handling, increased productivity, and better part quality for complex plastic parts. The system combines multicomponent injection-molding technologies (over-molding, multimaterial, and multishot) with several assembly steps or secondary operations. Their process just might help keep manufacturing of complex plastic parts in the United States.

The aproach can have as many as four small center stacks side by side, each with four faces and turning 90° per cycle. Another unique configuration, called Low Inertia Technology (LIT), comes from Caco-Pacific Corp. In this simpler design, a rotating bar with two core sets is attached to one half of each mold, rather than standing alone as in the other designs.

The Tech Group Inc., Scottsdale, Ariz., is a licensee of Gram's Spin Stack Technology and claims rotating the cube-shaped center core of the Spin Stack system at 90° intervals around a vertical axis lets the injection molding machine produce more parts and permits secondary operations at the non-molding positions per cycle.

Ferromatik Milacron and Foboha have 50 to 60 Turning Stack molds in operation, as many as 20 of them in North America. The firm forecasts 10% annual market growth for multi-component parts.

The Spin Stack concept is the most flexible on the market," according to Managing director Jes Gram of Gram Technology. "The turning mechanism, the hydraulics, and all of the components are contained in the mold, so this allows the technology to be used in any conventional press." The second material can be supplied from the side of the machine with a modular add-on injector, such as the new PlugExpress system from Windsor, which is sold in the U.S. by its sister firm, Sandretto.

For the first time, stack-mold technology has broken into larger parts molded on machines bigger than 1000 tons. Plastcoat, part of Decoma International in Mississauga, Ont., is using a Husky two-level stack mold with one cavity in each face to simultaneously produce front and rear wheel flares for Ford's XLT trucks. Another 1 + 1 stack mold is making rockers for Toyota's Camry line. The parts are each several feet long and use about 300 g of TPO. These parts are molded on Husky's 2200-ton EWLL (extra wide, long) two-platen machine.

Haven't found what you're looking for? Try 'Search' powered by : Related Resources: Gram Technology, Sandretto USA, Inc., Unique Mold Makers, Tradesco, The Tech Group Inc., Plastcoat, part of Decoma International in Mississauga, Ont., Ferromatik/Foboha, Caco Pacific Corp., Engel, Carmo Industries in Denmark, Demag

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