CompositesWorld
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NEWS 27 CompositesWorld.com Fig. 3 Wet pressed "backbone" Wet pressing is used to make the tunnel (top photo), which forms the backbone of the 7 Series Carbon Core BIW, as well as three of the roof bows and four sill reinforcements, while HP-RTM is used to make the roof rails (bottom photo) and central roof cross member. Source | BMW AG Fig. 4 Recycled SMC C-pillar Both the 7 Series C-pillar (shown here) and rear cross member/upper trunk cover use recycled carbon fiber SMC. Source | BMW AG Fig. 5 Automated milling maximizes throughput Automated CNC mills enable molded parts — tunnel shown here in machining (top photo) and quality assurance (bottom photo) — to be loaded/unloaded at the front of the machine while another is being milled at the back, for maximum throughput and efficiency. Source | BMW AG BMW 7 Series Plant and places the preforms into one of several drawers in a convec- tion oven. Here, the CFRP preforms and the steel B-pillars are preheated before pressing. e preforms are then transferred from the heating drawer to a forming station where they are placed onto and shaped by a set of pins that essentially form an articulated tool. After this is completed, the two shaped preforms are mated to two preheated steel B pillars and then fed into the press. A twin- cavity tool, supplied by Koller Formenbau (Dietfurt, Germany), molds a complete set of left and right B-pillars in one stroke. Wolf- erseder explains that the presses used here are the same as those employed in wet pressing, but the pre-and post-press equipment is completely different. After a high-temp, high-pressure cycle, the two finished parts are removed and set on a shelf where they will cool at ambient temperature. "e cooling stage is needed in order for the parts to finish hardening," says Wolferseder, "and also for the two workers at the end of the line to be able to handle them." e robot receives a signal that the temperature of the parts is cool enough and then transfers them to the conveyor belt where the workers will pick them up, perform a visual inspection for quality and will also remove the peel ply/foil on top of the prepreg. "e CFRP allows