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Article: 34 Gas-assist molding.(TOP 50 INNOVATIONS 1955-2005)
- Article from:
- Plastics Technology
- Article date:
- October 1, 2005
CopyrightCOPYRIGHT 2005 Gardner Publications, Inc. This material is published under license from the publisher through the Gale Group, Farmington Hills, Michigan. All inquiries regarding rights should be directed to the Gale Group. (Hide copyright information)
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An estimated 15% to 20% of U.S. injection molders use gas assist to core out thick sections, reduce sinks and warpage, and mold larger parts at lower pressures. Four milestones marking the development of gas-assist molding started in 1971 with a patent application filed by German inventor Ernest Mohrbach. He described internal gas injection to form a void within a molding. In a first test, the patented process was applied to a structural-foam shoe heel as a means to reduce cycle time and improve the surface. The gas pushed the melt against the mold, collapsing the foam but enhancing cooling.
In 1973, Asahi Dow in Japan filed a more detailed patent involving ...