Structural plastics display new process combinations.

If the recent Applied Technology and Design Conference reveals any trend for plastics processors, it is that many of the most innovative structural plastics parts and assemblies make use of combinations of different materials and manufacturing processes. The conference, held in St. Louis by the SPI's Structural Plastics Div., spotlighted many examples of interesting new hybrids in its annual design competition. Take, for example, the Total-Care Hospital Bed, which won the Judge's Award. Entered by HillRom Co. of Batesville, Ind., the bed is a product of blow molding, thermoforming, injection molding, and gasassist injection molding of four different materials. Six entries in the competition involved coinjection of different materials. Here's a look at some of the other winners.

* Coinjection and gas-assist molding: Among the six coinjected parts at the show two automotive ones stood out. The fold-away rearview mirror assembly entered by Siegel-Robert Inc. of St. Louis uses a coinjected PC/PET alloy over a 30% glass-filled ABS in a mirror mount that requires no painting and still passes weathering tests. The mirror head adds gas-assist molding to the mix of processes. Both the gas-assist and coinjection processes were performed on machines from Battenfeld of America, West Warwick, R.I.

* Coinjection and sequential valve gating: Visteon Automotive System's Milan, Mich., plastics plant won the environmental award with a coinjected front bumper fascia. Because the bumper is coinjected, it allows Visteon to incorporate more than 20% of painted in-plant scrap. The bumper tool also employs sequential valve gating. Hot-runner equipment from Dynisco's Kona Hot Runner Systems, Gloucester, Mass., and Incoe Corp., Troy, Mich., was used at different stages in the bumper's development.

* Structural foam and injection molding: The Conference Award winner, a Xerox Corp. digital copier entered by Mack Molding of Arlington, Vt., contains both low-pressure structural foam and injection molded parts, including the first all-plastic paper-path.

* More structural foam: In a tough-to-beat feat of parts consolidation, Abbot Diagnostics Div., Irving, Texas, brought out a baseplate for a blood analyzer, molded by FM Corp., Rogers, Ariz. The one-piece foam baseplate (which has ultrasonic inserts added after molding) consolidates the functions of what could have required over 100 metal parts.

Injection-compression molding: Japan's Idemitsu Petrochemical Co. showed off a construction panel designed to be part of a modular bathroom. By injecting into a gapped tool, which is closed after the melt has been introduced, Kyowa Molding Co. produced the door-sized part on a 3000-ton machine, rather than the 5000-ton press it would have needed if conventionally molded. Idemitsu's version of injection-compression, performed on a toggle machine, makes uses of a hydraulically actuated wedge that slips between the platen and the tool to provide the compression. Compared with thermoforming, the previous manufacturing method, the new molded panel shaved 15% off the part cost, even though the cycle time increased by about 10%. Through in-mold decorating, this polystyrene part has a marbled final finish right out of the tool.

* Thermoforming: Made from a coextruded sheet of ABS with a weatherable cap of ASA (both from Bayer Corp., Pittsburgh), the Sport Trailer from U-Haul International, Tempe, Ariz., consists mostly of two very large parts thermoformed by TLC Plastics Ltd., Gilbert, Ariz. At 7 ft long and 6 ft wide, the trailer weighs under 450 lb. Because the part has many undercuts, its epoxy/graphite tool requires 15 moving components.