Research On A New Method For On-line Identification Of Tool Center Error In Single-point Diamond Turning

Single-point diamond turning(SPDT)is an important technology for ultra-precision machining.It can directly machine ultra-smooth surfaces with nano level surface roughness and sub-micron level form accuracy using single crystal diamond as a tool on a machine with ultra-high motion control accuracy.With decades of research progress,it has become one of the most effective methods for machining optical surfaces with high precision and complex structures.SPDT is also widely used in high-tech areas such as aerospace,defense military,precision optics and so on.With the increasingly high requirements on the accuracy of machined surfaces with high efficiency and the development of intelligent manufacturing in various industries,the traditional off-line measurement method of tool center error has become an important factor restricting the efficiency and intelligence of SPDT due to the problems that it takes time and effort to rely on people to repeatedly disassemble the workpiece.In order to solve this problem,a method combining experimental analysis and mathematical modeling was adopted in this paper.Based on the online monitoring of the tool cutting force,The characteristic creation and mechanical performance of the tool height error and tool low error in the vertical direction were analyzed separately,and a new online identification method to eliminate tool center error was proposed.Firstly,the influence factors of cutting parameters on tool interference zone under the tool height error were analyzed through experiments.Based on the cutting motion relationship between the tool and the workpiece during the tool interference process,a mathematical model of the tool interference zone was established.Then,based on the mapping relationship between the three-dimensional interference topography of machined surface center and the cutting force under the tool height error,the influence of the secondary interference between the tool and the centre cone formed in previous face turning on the workpiece surface was studied.Based on the geometrical relationship between the tool clearance face,interference round platform and centre cone during the turning process,the evolution model of the interference curve between the tool and the workpiece during the interference process is derived.The cutting force model based on the projection of the interference extrusion area between the tool and the workpiece realizes the online prediction of the tool height error.Finally,this paper divided the tool center error into nine categories,and analyzed the corresponding relationship between the cutting force shape characteristics and the tool center error in turn,The identification models of different tool center errors were established,and the whole tool center error theory system was improved.Theoretical and experimental results show that there is an accurate correspondence between the workpiece topography,cutting force,and interference zone during the interference,and the cutting force model established in this paper can realize the online identification of the tool center error.This online identification method overcomes the time-consuming and laborintensive aspects of traditional offline measurement methods,greatly improves the efficiency of SPDT,and provides important guidance for production.Meanwhile,it also provides a solid technical foundation for the automation of ultra-precision machining.