Screening and optimization method of defect points of G code in three axis NC machining

G code is the input of the CNC system, and its quality affects the machining accuracy and efficiency. However, the G code generated by CAM has some defect points, which will seriously affect the processing quality and efficiency. To solve this problem, this paper proposes a method to screen and optimize the defect points of the G01 format G code of three-axis machining. First, a rough screening method based on the geometric characteristics of the trajectory is constructed. Second, a precise screening method through trend trajectories and box plot to screen out defect points is constructed. Finally, the NURBS curve is used to restore and discretize trajectories to obtain new points of G code. Two cases and experiments are used to verify the optimization effect. The experiments results show that after screening and optimization, the geometric characteristics of the two G codes, such as curvature and the difference between adjacent line segments, are obviously improved. The curves of setpoints speed and acceleration are smoother, the setpoints jerk is reduced, and the vibration is weakened. The processing time of the two G codes is shortened by 4.07% and 9.85% when the feed speed is 3000 mm/min and 2000 mm/min, respectively.