Parameter Optimization Of Mechanism Model For Double Ballbar Testing Accuracy Of Turntable

With the advancement of technology,five-axis CNC machine tools are compared with three-axis CNC machine tools.Due to the existence of two rotating axes,five-axis CNC machine tools can realize any attitude of the tool and workpiece in space,and are often used to process complex curved workpieces.The linkage motion accuracy of the two rotating axes will affect the accuracy of the workpiece,so it is of great significance to study an accuracy detection method that can cover the working range of the two rotating axes.In this paper,the double ballbar detection method of the two-axis linkage motion accuracy of the machine tool turntable is studied based on the mechanism theory,the space mechanism model for the ballbar to detect the precision of the machine tool turntable is established,and the space optimization method of the ballbar measurement based on the mechanism model is constructed.Experimental validation of machine tool ballbar measurements.The main contents are as follows.A space RRSPS mechanism model for the double ballbar to measure the accuracy of the linkage motion of the machine tool turntable is established,including the SPS kinematic chain of the double ballbar and the two rotating axes(R pairs)of the machine tool turntable,the structural parameters of the mechanism correspond to the installation position of the double ballbar.The direction and position deviation between the axes of the two rotating shafts of the machine tool turntable,and the input and output parameters of the mechanism are the rotation angle of the turntable rotating shaft and the measurement data of the ballbar,respectively.Establishing a comprehensive motion model of RRSPS,and fitting the discrete data measured by the double ballbar,the installation error of the ballbar,the direction and position deviation between the rotary pairs of the turntable can be identified at one time,and then the error motion of the kinematic pair can be identified.The theoretical solution of the spatial RRSPS five-bar mechanism for the two-axis linkage motion accuracy of the machine tool turntable is studied.When there are no machine tool geometric errors and ballbar installation errors,the ballbar rod length is a fixed value,and the spatial RRSPS five-bar mechanism degenerates into a spatial RRSS four-bar mechanism.Bar mechanism,at this time,the spatial RSSR four-bar mechanism has definite motion,and the ideal motion relationship between the rotation angles of the two rotating axes of the machine tool turntable is the displacement relationship formula of the spatial four-bar mechanism,which provides a theory for the precision ballbar measurement of the machine tool turntable.untie.An optimization model of the measurement space of the turntable precision ballbar based on the mechanism model is proposed.The objective function is to take the maximum measurement space of the double ballbar as the objective function,and the mechanism parameters representing the installation position of the double ballbar in the RSSR mechanism are used as the optimization variables.is a constraint condition.The optimal installation position of the double ballbar and the maximum working range of the double ballbar measurement turntable are obtained by the optimization solution.This method provides a theoretical basis for determining the accuracy of the machine tool turntable and the measurement range of the double ballbar.Combined with the error identification method of machine tool turntable based on the comprehensive model of RRSPS mechanism proposed in this paper,the test is carried out on the actual five-axis CNC machine tool,and the test principle and steps are given to prove the feasibility of the method.