Fiber bundle deposition model and variable speed printing strategy for in-situ impregnation 3D printing of continuous fiber reinforced thermoplastic composites

In the in-situ impregnation 3D printing of continuous fiber reinforced thermoplastic composites (CFRTPCs) at constant printing speed, in order to pursue higher printing efficiency, a higher speed for printing is adopted generally, which has no effect on the printing of the straight section, but at the same speed of printing at the corner, the printing speed will cause the fiber bundle to deviate from the printing path at the corner, which affects the accurate laying of fiber bundle along the printing path. Obviously, reducing the printing speed is an effective method to improve the print quality at the turn, but printing the entire part at the reduced speed will greatly limit the overall printing speed. However, the problem of different corner angles and shifting points from the straight section of high-speed printing to the corner section of low-speed printing has been puzzling researchers. In this paper, a fiber bundle deposition model has been proposed to reveal the deposition of fiber bundles, and the maximum offsets of fiber bundles were predicted under different turning angles. Compared with the measured results, the prediction error at different turning angles ranged from -1.07 % to 10.30 %. Then, combining with the finite element analysis method, the fiber bundle deposition model was adopted to study the effects of printing speeds, and the maximum printing speeds for different printing angles and the variable printing speed strategy have been put forward. The results have revealed that, by using the optimized variable printing speed strategy, the surface quality of the fabricated parts and the deposition of the fiber bundles along the designed printing path were significantly improved. The fiber bundle deposition model and the variable speed printing strategy could be helpful for the high-precision 3D printing of CFRTPCs.