In a collaborative project, Engel of Austria (parent of Engel Machinery, York, Pa.) has developed a new in-mold assembly technique for injection molding hollow parts. The new joinmelt process involves molding two halves of the hollow chamber in cavities on opposite sides of the mold. After the initial molding cycle, one cavity plate slides vertically to align the two part halves facing each other. Then a hot-gas infrared heating element is inserted into the mold between the two parts to heat their edges. The heater is withdrawn and the mold closes to fuse the two parts. This is said to produce a strong, clean weld without warpage problems, since the parts remain fixed in the mold. Engel and its partners see “huge potential” in glass-filled nylon fluid-carrying parts for auto engine compartments. Unlike previous welding processes for such parts, joinmelt produces no bulge at the weld line that is prone to friction with moving parts (such as valve tappets) of a finished assembly. Engel worked with German moldmaker Hummel-Formen, which applied for a patent on in-mold hot-gas welding, and German welding equipment supplier KVT Bielefeld.
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