Identification And Compensation Of Geometric Errors In A Five-axis CNC Machine With Double Rotary Table

Five-axis machine tool is with superior efficiency and precision,so is used widely to process complex curved surfaces.However,the two rotating axes of the five-axis machine tool leading,additional geometric errors that affect machining accuracy.To address the problem,the geometric error detection algorithm of the BC style double turntable five-axis CNC machine tool is discussed in this study.The geometric error model and the kinematics model of the CNC machine tool are defined using the homogeneous coordinate transformation,and the double ball bar calculation is used to propose a method based on them.In addition,the virtual observation method’s geometric error detection algorithm is used to compensate the machine tool error based on the proven kinematic model.The following is a list of the basic work:First,the error source and kinematics analysis of the Mikron HEM 500 U five-axis machining center is performed using the theory of homogeneous coordinate transformation,and the position transformation matrix between the machine tool kinematic chain and the workpiece kinematic chain is described.So,geometric error and kinematics models provide theoretical support for subsequent error compensation.On the basis of error modeling,a mathematical model of geometric error elements and rod length variance is developed,and then measurement strategies for the geometric errors of the translation and rotation axes are constructed based on the double ball bar measurement.Furthermore,the algebraic model of the length of the rod is combined after parametric modeling of the machine tool’s error components,and then the geometric error identification model of the translational axis is defined as well.In addition,a ball bar was mounted in the axial,radial,and tangential directions of the B and C shifts respectively,for the rotating shaft,and the calculation was performed.Then,independent of the location,a model for identifying the geometric error and the length of the rotating shaft was created.So a theoretical foundation for determining the machine tool’s geometric error is offered.Secondly,according to the designed measurement strategy,the translation and rotation axis of the machine tool was measured and identified.For the measurement of the translational axis,the double ball bar is used to measure the three planes of the translational axis,and then the polynomial coefficients of each error element of the translational axis are solved by the virtual observation method,and the change of the rod length is reversed to prove the identification method is correct.In addition,for the measurement of the rotary axis,the measurement strategy of "one axis rotates and the other axis fixed" was used to measure the rotary axis and identify the positionindependent geometric errors of the rotary axis of the five-axis machine tool.Finally,on the CNC machine tool,error compensation is performed based on the actual inverse kinematics model defined.Tool position data are generated using CAM software,and the tool position data are directly substituted into the inverse kinematics model,yielding the NC border.Furthermore,the simulation experiment is compared,and the method’s usefulness is evidenced by a study of impeller blade finishing machining.The circular interpolation motion was then compensated,the translational axis error detection result was substituted into the definite inverse motion model,the compensated NC code was created by importing the circular interpolation tool location results,and the compensation was carried out on the machine tool.After compensation,the roundness error of the entire machine tool and the straightness of the X-axis have been improved,which further proves the effectiveness of the compensation method.