Research On Linkage Modes And Motion Optimization Of Redundant Linkage Axis In Six-axis CNC Machine Tools

The CNC machine tools are one of key equipment of modern manufacturing industry.To optimize the machining accuracy and processing time is important research and application significances.With the support of relative projects,the paper mainly optimized the motion trajectory of tool and processing time of a type of six-axis CNC machine tool that it has three linear axes and three rotation axes.In the beginning of the paper,the kinematic model of the CNC machine tool is established based on the structure and the distribution of linkage axes of the six-axis CNC machine tool.The characteristic of the redundant linkage mode,the kinematic models of all linkage modes and linkage axes configuration in the CNC machine tool are researched.Based on the kinematic model,with the features of model,the research contents of the paper are showed as below:Firstly,aiming at the error between the actual trajectory and ideal trajectory of the tool center point,an optimization method is presented.In the method,the error models of all linkage modes and linkage axes configurations are established.The two constraint conditions are presented.The method makes the linkage modes and the linkage axes configurations changed adaptively that it can satisfy the positon of tool center point and direction of tool axis and optimize the trajectory error at the same time.Secondly,aiming at the error between the actual trajectory and ideal trajectory of the contact point,an optimization method that it applies the motion of redundant axis to optimize the error is presented.In the method,the relation of the trajectory of tool center point and tool axis to the trajectory of contact point is established.It shows the error of tool center point and tool axis influence the error of contact point.The motion of redundant linkage axis makes the change of the three rotation linage axis become minimized.The trajectory error of the contact point is optimized.Thirdly,to eliminate or slow down the increase of the processing time that it caused by the CNC system of the machine tool limit the velocity of linkage axes,an optimization method that it applies the motion of the redundant linkage axis to adjust the velocity of linkage axes is presented.In the method,the relation of the velocity of linkage axes to processing time is established;with the motion of redundant linkage axis,it makes the motion and velocity of linkage axes are changed that the velocity is not exceed the set value in the CNC system.The processing time is optimized.Lastly,the methods in the paper were realized in the postprocessor software of the CNC machine tools.Experiments of the proposed methods had done on a six-axis CNC polishing machine tool.Experimental results show that the proposed methods in the paper are feasible,and can increase the machining quality and processing time of polishing.