Geometric Error Modeling And Source Traceability Of Heavy-duty Vertical Lathe

Due to the large size of heavy-duty machine tools and large span,it has a larger working space compared to small and medium-sized machine tools.The size of the working space,that is,the size of the motion stroke determines the degree of influence of each error element on the machining accuracy of the machine tool.For example,under the action of the large stroke of the machine tool,the parallelism error,perpendicularity error and angle error of each axis of the machine tool will magnify other error elements,so heavy-duty machine tools have relatively larger geometric errors.And heavy-duty vertical lathes are generally aimed at specific processing objects,such as processing wind turbine turntable bearing raceways up to 5m in diameter.In the process of rotary machining,due to the large diameter of the workpiece itself,a smalle error on the machine tool will also produce a large error map on the workpiece-tool contact point trajectory,which will affect the machining accuracy of rotary parts.Therefore,this article will measure and model the errors of heavy vertical machine tools,and obtain the digital simulation surface of the workpiece through numerical simulation,evaluate the processing accuracy of digital workpieces,analyze the effects of errors,establish error mapping relationships,and finally realize the traceability of errors.The Euler angle representation method based on rigid body motion divides the geometric error elements of the heavy vertical lathe to be measured.The XD-6D laser interferometer was used to measure the geometric errors of the heavy vertical lathe.A polynomial high-order fitting method is used to process the measurement results,and a polynomial model of each geometric error element of a heavy-duty vertical lathe is obtained.Realize the measurement of various geometric errors of the machine tool.It lays the foundation for the digitization of the surface of the workpiece and the traceability of the machining error.Based on multi-body system theory and homogeneous transformation matrix,the geometric error model,low-order body array and geometric error transfer matrix of heavy-duty vertical lathes are established.The geometric model of the tool was analyzed,and the fixture eccentricity error model was established according to the influence of fixture installation eccentricity on the machining accuracy,and the establishment of the error model of the entire machine tool system was completed.Through numerical simulation,the digital machining surface of the virtual workpiece is obtained,which comprehensively considers the geometric error of the machine tool,the geometric characteristics of the tool,and the eccentricity of the fixture,and the correctness of the model is verified.A digital model of the machined surface considering the geometric errors of the machine tool was established.Several machining accuracy indexes of digital workpieces are evaluated.The optimization algorithm is used to evaluate the dimensional accuracy,roundness accuracy,cylindricity accuracy and axis perpendicularity of digital rotary workpieces.The evaluation of the machining accuracy of digital workpieces is realized,and the preconditions for the following error traceability are provided.The influence of various machine tool errors on workpiece cylindricity accuracy and dimensional accuracy is analyzed,and the mapping relationship between workpiece machining error and error source of heavy vertical lathe is established.According to the mapping relationship,the machining error of the machine tool is traced,and the machining error tracing method of the heavy vertical lathe is obtained.