If the composites industry is to mature, it must pursue shorter automated molding cycles. Toward that end, much attention has been focused recently on resin transfer molding (RTM). Pinette Emidecau Inc. (Troy, Mich.) reports that it has developed an automated, high-speed RTM cell for aerospace and automotive manufacturing applications that is designed to increase molded part throughput and improve process consistency.
The work cell has four stations where the following are accomplished: robotic preform loading; mold closure and transfer to press; RTM injection; and postinjection oven cure. The robot is a 6-axis, articulating arm type, and it removes preforms from a conveyor that enters the cell from the left. After the preform is placed on the lower tool, the mold is shuttled to the next station, where the top tool is lowered into place and locked. Both tools are supplied by Compose (Bellignat, France) designed for maximum temperature cycling. An automated shuttle then transfers the closed mold to the RTM press. Here, an ISOJET Équipements (Corbas, France) resin injection system injects the epoxy into the mold. The injection time for an aerospace part used to develop and prove the cell took about three minutes, but Pinette Emidecau says an automotive part — thinner, smaller and, likely, with a smaller fiber volume fraction — could conceivably be wet out more easily and, therefore, could be injected in about 45 seconds.
Following injection and initial cure, the shuttle system moves the mold to the postinjection curing oven, where the cure process is completed and the injection station is freed up to receive the next mold. The oven capacity, as currently configured, is two molds. Pinette Emidecau says the two-mold oven, combined with the movement and transfer of molds at other stations, allows up to four molds in the cell at the same time, maximizing throughput and ensuring that no one station becomes a bottleneck in the cycle.
Pinette Emidecau R&T manager Phillippe Capon says the oven can be modified to accommodate up to three molds loaded vertically, or it could be upsized to hold more or larger molds, depending on application and customer requirements. In addition, although the cell is configured for thermoset resins, Capon says the ISOJET system can be modified to inject thermoplastic resins. The cell is in operation at, and was developed in cooperation with, Deutsches Zentrum für Luft und Raumfahrt (DLR, Stade, Germany), which is proving the system via the manufacture of a carbon fiber/epoxy aerospace part.