Research On Geometric Error Of Double Turntable Five-axis CNC Machine Tool Based On PMAC

Five-axis machine tool center is the main machining equipment for processing complex curved parts.China's equipment manufacturing industry has been in the state of catching up with foreign top technology,especially for the development of CNC system is still in the technical development stage.Domestic and foreign mature CNC system internal underlying data confidentiality,each brand is not common,the user can not be developed according to their own needs.In this case,the choice of open CNC system is a better choice.CNC machine accuracy is affected by many aspects.Geometric error is one of the important aspects.Error compensation of machine tools for geometric errors is one of the common studies at home and abroad.The research object of this paper is a small double rotary table CNC milling machine built on PMAC.Its features include small size,high accuracy and easy operation.The machine is connected to the lower motion control card using an IPC,and the application of PMAC function can realize a variety of complex machining.In this paper,we first analyze the hardware of the machine tool,write the upper computer interaction interface using C++ Qt for the actual situation of the machine tool,develop several modules such as communication,machining and manual feeding,and model the kinematics of the machine tool using the flush coordinate transformation method.Based on the functions of the CNC system,the geometric errors of the small double rotary table five-axis CNC milling machine are analyzed and the geometric errors of the machine are modeled by the flush transformation method.Starting from the two parts of geometric error of linear axis and geometric error of rotary axis,the analysis of linear error and angular error of each kinematic sub is carried out,the expression of geometric error is deduced,the suitable measuring instrument is selected,and the design of measurement method of geometric error of machine tool is carried out.Based on the model,the laser measuring device is selected to measure the geometric error of linear axis,and the double-ballbar is selected to measure the geometric error of rotary axis based on a specific trajectory,and the obtained data signal is analyzed and processed.The 21 errors of the linear axis were obtained by processing the laser measuring device and 8 errors were obtained by processing the data of the double-ballbar.Finally,the obtained geometric error values and geometric error expressions are substituted into the positive and negative kinematic algorithm to obtain the compensation strategy for the geometric errors of the machine tool.There are numerous studies on the error compensation of dual rotary table five-axis and interpolation functions.This paper uses a combination of methods for geometric error measurement with practical engineering implications.