CompositesWorld
Issue link: https://cw.epubxp.com/i/841219
JULY 2017 30 CompositesWorld FEATURE: AUTOMATED PREFORMING, PART 1 automotive parts, the Compositence system uses tapes ≥12 mm wide with 150-600 g/m 2 fiber areal weight because, says Dobiasch, "placement of narrow materials takes too long. For us, the speed of the preform layup must be in the same range as the molding machines, which for injection molding is 1 minute." However, he cautions, "Wide tapes can produce more waste for certain types of parts. You must tailor your process for the part you are making." In pursuit of speed, Compositence has patented its edge fixation technology for AFP. "We fix the fibers only at the begin- ning and end of place- ment," says Dobiasch, explaining that the AFP head lifts slightly up to fly freely, "accel- erating across the layup in between, which speeds up produc- tivity." However, this edge fixation technique cannot be used with towpreg, because it requires continuous compaction to avoid trapping air in the layup. Another key driver in preforming productivity is drapability. "Our draping capability must be the same as noncrimp fabric [NCF] or better," notes Dobiasch. Since 2010, Compositence has worked on AFP preforming with BMW (Munich, Germany) and SGL Group (Wiesbaden, Germany). "With them, we have developed what we call multifunctional tow, where multiple rovings are fixed together with a kind of textile process," he explains (Fig. 4, p. 28). e stitching binds the tows to maintain precise width — typically 46 mm for dry fiber — and also aids resin flow vertically through the fibers, crucial in the next step, either resin injection or infusion. "e fibers are not blocked from moving layer to layer as they are in stitched fabric," Dobiasch explains, "so drapability is very good and confirmed by BMW as being the same or better than NCF. ey have also verified the improved resin flow." He concedes the material does require more time and cost to produce vs. towpreg, "but it is better to give the material some functions, and you then get cash back during the processing via less scrap and better cycle time in wet compression molding and RTM." Dobiasch claims a 25% reduction in scrap vs. NCF due to AFP's net shaping ability compared to cutting waste with fabric. He adds, "We have also demonstrated with BMW that we can preform 3.5 million parts per year on one machine with an output of 250 kg/hr." Back to the future, Fiberforge 4.0 e original automated tape/fiber preforming process was the Fiberforge RELAY Station, mentioned earlier, which CW reported Read this article online | short. compositesworld.com/PreformPt1 CW's 2013 coverage of this subject, "Structural preform technologies emerge from the shadows," offers a good preforming primer on preforming and discusses a variety of early automation efforts, including the Dieffenbacher PreformCenter | short.compositesworld.com/Mqzr7Fg7 Read CW's earliest coverage of the Fiberforge RELAY station online in "Tailored carbon fiber blanks set to move into steel stamping arena" | short.compositesworld.com/LvFR7nP1 Walton Process Technologies, Inc. Best Customer Service in The Industry www.autoclave s .com Mansfield TX 682-518-9002 Service/Repair Retrofit/Relocate Autoclaves Bond Presses Batch Process Controls Ovens Parts