Research Of Multi-axis Tool Paths Smoothing Method For Improving The Feedrate Smoothness Of The Physical Axis Of CNC Machine

In CNC machining,the toolpath with good federate planning performance is the basis for ensuring the smooth movement of each axis of the machine tool.In multi-axis machining with rotary axes participating in linkage,due to the nonlinear relationship between the movement of the tool point and the movement of each physical axis of the machine tool,the smooth toolpath in the workpiece coordinate system(WCS)cannot guarantee the smooth movement of each axis of the machine tool.When the given processing speed is high,the above-mentioned non-linear relationship may cause the vibration of the machine tool and the command acceleration at some special positions to exceed the performance constraints of the servo motor,making the processing unable to proceed normally.Therefore,this paper proposes an algorithm for smoothing the tool path in the machine coordinate system(MCS),aiming at improving the speed planning performance of the multi-axis linear tool path,so as to better meet the processing requirements of the "efficiency first" machining scenario.When the given processing speed is relatively high,the unsmooth movement of the single axis caused by the above-mentioned nonlinear relationship may cause the machine tool to vibrate and make the processing impossible.In order to quickly evaluate the feedrate planning performance of the tool path,the physical axis speed and acceleration trial calculation formulas are derived,and the relationship between the tool path and the motion performance of the machine tool is established.Then,on the basis of the trial calculation formula,the concept of estimated acceleration was introduced,and the evaluation criteria for the smoothness of the physical axis speed based on the estimated acceleration were formulated.Aiming at the problem of speed fluctuations,acceleration fluctuations and excessive jerk between multiple continuous multi-segment linear tool paths of machine tool physical axes,a method of identifying and adjusting the possible velocity discontinuity points(PVDP)in the nodes of the linear tool path in MCS(composed of the position of each axis of the machine tool)is proposed,which can directly improve the speed smoothness of physical axes of machine tool.This method takes the single-axis component of the toolpath nodes as an independent processing object.By analyzing the property of the estimated acceleration of the target axis,the PVDP is identified.Then,considering the local uniformity of the estimated acceleration,adjust the coordinate component of the target axis of the PVDP.For the complete tool path,in order to obtain the best feedrate planning performance under the tolerance constraint,an adaptive smoothing algorithm is proposed.The algorithm first performs segmentation processing on the tool path,and then iteratively identifies and adjusts the PVDP of each segment under tolerance constraints.By reducing the proportion of PVDP in the programming points,the speed planning performance of the tool path is gradually improved.Designed and developed the tool path offline smoothing software to realize the smooth processing of the tool path.The method proposed in this paper has been verified by simulation processing,and the experimental results show that the method greatly improves the speed planning performance of the tool path and greatly improves the smoothness of the speed of each axis of the machine tool.