The Geometric Error Modeling And Compensation In Post-processing Solution For Large Multi-axis Machine Tools

As the rapid development of aerospace and ship industries, the large-scale andcomplex parts have been widely used. In order to meet special machining requirements ofthe components, machine tools trend to be multi-axis, large-scale and specialization ofmotion structures. Due to the multi-axis, large stroke, complex structures, the geometricerrors, which have many components and complex configurations, vary greatly along theposition of axes. After magnified by axes coupling, the geometric errors exert greatereffects on contour errors and thus hamper the improvement of the machining accuracy oflarge multi-axis machine tools.Aiming at impact of the position change of motion axes on geometric errors, thegeometric errors are divided into two parts, position-dependent errors andposition-independent errors. Then, the theoretical kinematics model is revised according totheir respective features, constructing machine tool parameterization universal dynamicmodel of geometric errors considering the position variation’s influence on them. Thedeveloping process of parameterization geometric errors of large turning-millingcomposite machine tool is explained.The parameterization geometric errors are calibrated and analyzed based on T3laser tracker and STS six-dimension sensor, and the position errors are obtained by linefitting and circle fitting. The transformation function from machine tool elements errors toposition axes is procured through B-spline fitting and the measuring random errors arefiltered to some extent. The orthogonal experiments on angle error sensibility oflarge-scale machine tool are conducted and the impact of angle errors on machineprecision is ascertained by range analysis and variance analysisThe post-processing error compensation solving algorithm is proposed based onthe parameterization geometric errors dynamic model. The reverse solution of kinematicsmodel including geometric errors is achieved through simplifying the redundant equationof parameterization geometric errors into linear equations and solo parameter one-dimensional search. The errors compensation simulation of turning-milling compositemachine tool is conducted. The effectiveness error compensation algorithm on machiningerrors due to position errors and various element errors is verified.Finally, universal post-processing software have been developed, which canrealize the post process considering error compensation and also machining simulation.The3D model of machine tool is constructed by the software. The machine tool structureand controller is configured, and the tool path file to NC code is transformed throughuniversal post-processing algorithm.