Research On Five-axis RTCP Algorithm Based On Open Ultra-precision CNC System And Its Application

RTCP(Rotational Tool Center Point)function is an extremely important function of five-axis machine tools,which can effectively improve the machining efficiency and accuracy of five-axis machine tools.High-grade five-axis numerical control systems produced by numerical control manufacturers such as Heidenhain,SIEMENS,FANUC and Fidia all have RTCP function.Tayler/Hobson-Pneumo,Moore and Precitech and other world famous ultra-precision machine tool research and development units,some of the newly developed five-axis ultra-precision machine tools have also developed RTCP functions.Domestic research on RTCP function of five-axis machining center has achieved certain results,but research on five-axis RTCP function based on ultra-precision numerical control is less.Therefore,the research goal of this paper is to realize RTCP function on ultra-precision five-axis machine tools.The main contents include the establishment of RTCP kinematics algorithm,the integration of algorithm and ultraprecision numerical control system,the effect of RTCP controlling non-linear error,the factors affecting non-linear error and the application of RTCP function.Firstly,according to the structure and movement characteristics of the machine tool,the generation principle of nonlinear error is analyzed,and the nonlinear error calculation models of B and C rotating shafts are established respectively.On the basis of nonlinear error calculation model,RTCP kinematics algorithm is established.The correctness of the established RTCP kinematics algorithm is verified by simulation using VETICUT cutting simulation software.Secondly,in order to realize RTCP function in the open ultra-precision system,the motion control principle of Power UMAC controller is analyzed,and the integration of RTCP algorithm and the numerical control system of five-axis machine tool is completed.This paper designs a testing method for machine tool structural parameters,and measures parameters such as B-axis rotation center,C-axis rotation center,tool swing length,etc.,thus realizing RTCP function on a five-axis machine tool.In addition,based on the realization of RTCP function,in order to study the effect of controlling non-linear error by RTCP function and the factors affecting non-linear error,the magnitude of non-linear error value,the factors affecting non-linear error and the effect of controlling non-linear error by RTCP function are theoretically analyzed.On the basis of theoretical analysis,a non-linear error measurement method is designed.The non-linear errors of B-axis swing,C-axis rotation and BC-axis linkage are measured respectively.The effectiveness of RTCP in controlling non-linear errors is verified and the factors affecting non-linear errors are obtained.Finally,on the basis that the RTCP function can effectively control the non-linear error,in order to further study the applicability of RTCP function.Milling experiments were carried out on five machine tools,and the correct part shapes were machined,which verified the effectiveness of RTCP function in actual machining.