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opened its doors in November 2012 to develop preforming processes, reports Vanja Ugresic, a Centre research engineer. A key element will be a fully automated PreformCenter, designed by Diefenbacher GmbH (Eppingen, Germany, and Windsor, Ontario, Canada) and slated to be up and running in early 2014. According to Diefenbacher's Matthias Graf, managing director of the Business Unit Forming, the goal for the PreformCenter is a less than three-minute process cycle, from the unwinding of fabrics to the fnished net-shape preform, syncing the preform cycle time to the mold cycle time. Te PreformCenter comprises several modules: the frst is a CNC cutting table — more than one table can be included as the project grows — to cut the plies necessary to make the part preform. "We use a roll knife, which we believe causes less drag and thus no fber disorientation," explains Graf. A robot arm equipped with a vacuum pick-andplace end-efector then transfers the cut plies from the cutting table to the binder application module, a cabinet containing spray equipment with nozzles that spray an epoxy-based binder upward onto the preform's bottom surface. Although the binder is characterized by thermoplastic behavior, it is reportedly compatible with the part resin. Te robotic arm moves the individual plies back and forth to direct the binder where needed and, Ugresic explains, "As part of the Centre's research, we will optimize the binder dosing to achieve the lowest amount of binder possible, on the order of about 3 percent of preform weight, to minimize any efect of binder on the part quality." Te robot then places the tacky laminate stack on a "draping" module, which automatically forms the 2-D layup into a 3-D shape — the most challenging step of the process. Although Diefenbacher won't release specifc details about the draping and forming methodology at this point, Graf revealed that afer considerable research and modeling, "we are able to minimize fber stress during the preforming shaping, and control and infuence fber orientation with our system." Tis, he says, has eliminated preform wrinkling without sacrifcing cycle time. Ugresic adds that a rigid, heated lower form with an "adaptive" upper mold shapes the preform at a low compression force. Te applied heat ranges from 80°C to 120°C (175°F to 248°F), depending on the binder. "Achieving wrinkle-free preforms regardless of materials used will be a strong R&D; focus at the Centre," she asserts. Afer the PreformCenter is up and running, the Fraunhofer Project Centre for Composites Research will be available to automotive customers who are interested in trialing preform methods and materials, says Ugresic. "We are open to cooperate with automotive OEMs, and strategic alliances are already under evaluation. Depending on the complexity of the project, Diefenbacher may be involved as a development partner." OvermOlding cOntinuOus reinfOrcement A fve-year-old startup, EELCEE AB (Trollhättan, Sweden, and Lausanne, Switzerland), is marketing a uniquely diferent approach to preforms. An automated process cell pulls multiple continuous fber rovings or tows from a creel through a series of dies that wet High-performance core materials and sandwich composite solutions from DIAB Wind | Marine | Aerospace | Transportation Construction | Subsea | Industry www.diabgroup.com CT oCTober 2013 Making your products stronger, lighter and more competitive 27