After the continuous fiber bundle (carbon fiber or glass fiber) is unwound by the unwinding device, it is pre tensioned and pre dispersed by the pre tensioning roller, and then the upper and lower surfaces of the continuous fiber bundle are preheated by the infrared radiation device, with a preheating temperature of 100-200 ℃.
The preheated continuous fiber is expanded by the air flow spreading device, and the air flow direction is perpendicular to the surface of the fiber bundle. Under the action of the initial fiber, the air flow velocity on both sides is greater than the air flow blocked by the fiber in the middle, so that the pressure on both sides is lower. Under the action of the air pressure, the fiber bundle starts to expand gradually to both sides, and then the fiber bundle is evenly expanded. The final expansion width of a single 6K fiber bundle is about 15mm, The thickness is 0.03-0.06mm.
The parallel co-rotating high-temperature twin screw extruder melts and plasticizes thermoplastic resins (PLA, PA, PU, peek, etc.) and then feeds the filament wetting mold (the heating temperature can reach more than 400 ℃). The expanded fiber bundle is introduced into the filament wetting mold at the same time. The resin matrix is used to complete the process of wetting the fiber bundle under the action of the wavy flow channel, and then is formed through the circular shaping die. The filament is cooled and shaped by the cooling device, The shaped filament is a continuous fiber prepreg filament or other uses that can be used for 3D printing. The diameter of the filament can be designed and controlled at will, usually Ф 0.5-1.75mm.
The process route of continuous fiber reinforced thermoplastic resin prepreg filament is shown in Figure 1.