Abstract: In order to reduce the defects of fluff and high temperature ablation of aramid fiber reinforced materials during milling, and to improve the cutting performance and machining quality, the material is processed by CNC milling machine. The liquid nitrogen is used as a cryogenic cutting fluid. The ultra-deep microscope digital microscope,3D surface contourgraph and dynamometer are used to measure the surface morphology, surface roughness and cutting force of cut specimens, respectively. A material model of milling process is established. The defects of dry milling are analyzed,and the liquid nitrogen cryogenic cutting mechanism is discussed. The results show that the machining quality of cryogenic cutting is excellent compared to dry ones at the same cutting speed. In two kinds of cutting conditions, the main cutting force declines with the increase in speed, and for the cryogenic one the trend is more obvious. At the same speed, the main cutting force in cryogenic milling is higher than that in dry milling. For the adhesive point of fiber woven it is lower cutter stress tolerance, and the fiber has automatic collision avoidance and elongation properties at high temperature and pressure, which lead to the inaccurate controll of milled surface quality. Besides the improvement of cryogenic cutting force and cutting temperature drop have played a positive role for the improvement of the aramid fiber cutting defects.

Key words: manufacturing technology and equipment, aramid fibers, cryogenic cutting, defect, surface quality, cutting force