Geometric Error Modeling,Detection And Identificationin Of Five-axis CNC Machine Tool

With the wide application of the precision machining technology and the rapid development of CNC machine technology,the requirements on the machining accuracy of modern machinery manufacturing industry is increasing.As error compensation technology is one of the most economic and effective methods to improve the precision of CNC machine,taking some five-axis CNC machine tool as the research object,this paper researches the error compensation from four aspects,which are the geometric error modeling,detecting and identification of error elements,scheme designing of error compensation and the compensation validation experiments.The main work and achievements are as follows:1)Taking the QLM27100-5X type of five-axis CNC machine tool as the object,describe its topological structure by the lower numbered body array and analysis the motion transformation between its adjacent body based on the theory of multiple rigid body kinematics and homogeneous coordinate transformation.Thus,the error transformation matrix between the components is defined.Finally,a geometric error model of five-axis NC machine tool is established by the relative position between the tool and the workpiece,which can provide the modeling basis for error compensation.2)In order to obtain the value of geometric error parameters in the error model,Laser Interferometer and DBB are used respectively to measure errors of moving axis and rotary axis.Moreover this paper focuses mostly on the issue of coupling errors caused by the linkage of moving axis when measuring the geometric errors of the rotary axis,proposing an error decoupling strategy based on the actual position and orientation of the DBB.At last,it was verified that the identification accuracy has been improved effectively after decoupling.3)Based on the idea of compensating errors by software,error compensation schemes for typical motions of moving axis(G00,G01,G02 /G03)and the rotary motions of A-axis and C-axis are proposed and their corresponding compensation modelings are established.Then error compensation is realized through iterative modification of NC instructions.On basis of these,the error decoupling and compensation scheme is discussed when moving axis and rotary axis move at the same time.Finally,based on MATLAB,a geometric error compensation software of five-axis CNC machine tools was developed.4)With the QLM27100-5X five-axis machine tool as the experimental platform,four compensation experiments have done which respectively are the linear interpolation motion,circular interpolation motion of X-axis and Y-axis,rotary motion of C-axis and multi-axis linkage motion of A-axis,Y-axis and Z-axis.The positioning precision of moving axis and roundness error precision measured by the DBB all have been increased by 30%-50%,which verifies the feasibility of the compensation scheme and the correctness of the compensation model.