Fiber Spraying Process for Efficient Preform Production
The Institute for Plastics Processing (Institut für Kunststoffverarbeitung/IKV) has developed a novel fiber spraying process that allows the orientation of fibers during fiber deposition to be adjusted as desired. The reinforcing fibers are first unreeled from a coil as rovings and then fed to a cutter. A thermoplastic binder thread can be used as the binder, for instance. The reinforcing fibers and binder are first cut to a length of 50 mm in the cutter. They are then drawn in by the vacuum created by a venturi nozzle located below the cutter. The stream of air with the fibers then passes through the fiber guide unit. Here, the fibers become oriented in the stream of air. Next, the oriented fibers strike the deposition tool. A vacuum exists at the deposition tool to hold the fibers in place temporarily. The binder is activated by means of hot air.
The 3-D fiber spraying process achieves discharge rates of up to 150 kg/h, allowing short cycle times and high production quantities. In contrast to conventional fiber spraying processes, the 3-D fiber spraying process permits orientation of the sprayed fibers in the direction of the load paths. Direct processing of rovings eliminates the need for textile manufacturing processes for blanks or woven inserts. In addition, waste can be reduced significantly. When producing preforms by means of the 3-D fiber spraying process, functional elements such as openings, force directing elements and reinforcing structures can be incorporated individually into the preforms in a manner suitable for the material. Subsequent cutting steps and additional cutouts in the preforms are not necessary. With conventional preforming processes, on the other hand, the reinforcing fibers are cut either during preforming or in subsequent processes in order to incorporate functional elements.