Research on feedrate planning algorithm with multi-constraints for CNC machining

As a key technique in multi-axis CNC machining, feedrate planning plays an important role to improve the machining accuracy for a given mechanical part, and receives extensive attention of domestic and overseas scholars. However, the current planning methods are mainly focused on the process limits, and rarely consider the constraints of axis velocity and axis acceleration in the planning. To cope with this issue, an adaptive feedrate planning algorithm is developed on the basis of proportional adjustment strategy in this paper. Firstly, curve scanning is performed on a given NURBS tool path, and the maximum reachable feedrate at each sample point can be calculated according to a decoupled mathematical model, which concludes the parallel constrains of the chord error, axis velocity and axis acceleration limits. Then, the initial feedrate curve is derived through B-spline fitting with these discrete velocity points. Finally, a proportional adjustment strategy is used to adjust the initial feedrate curve and realize the feedrate scheduling with multi-constraints. The performance of the proposed method is validated by performing experiments on a two-dimensional NURBS tool path, and the results demonstrate that both the chord error and drive constraints are confined into the preset ranges, which not only improve the kinematic characteristic of drive axes, but also further enhance the machining accuracy and efficiency.