Studies On The Lapping Technology Of Arc-edge Diamond Tool In Ultra-precision Optical Fabrication

Diamond tool is the key to ultra-precision turning technology.The precision of diamond tool is an important factor in achieve high surface accuracy and low surface roughness.The arc-edge diamond tool can realize the processing of complex surfaces such as aspherical surfaces and freeform surfaces,the arc-edge diamond tool has the widest application in ultraprecision turning technology.With the continuous development of modern optical fabrication technology,the requirement for the precision of diamond tool is becoming higher and higher.High precision arc-edge diamond tool require a tool contour error Ra of less than 0.05?m in the range of 60 degree and a tool surface roughness of less than 10 nm.In this paper,the arcedge diamond tool was taken as the research object,the lapping technology of the diamond tools are studied.Firstly,the anisotropy of diamond crystal is analyzed.The unique crystal structure of diamond resulted the excellent physical and chemical properties of natural diamond,but also led to the anisotropy of physical and chemical properties of diamond crystals in different crystal directions.According to the periodic bond chain theory and dynamic micro-mechanical strength theory,the lapping direction and micro-mechanical strength of diamond crystal are analyzed.Based on the above theory,the crystal plane layout of arc-edge diamond was designed,and the geometric parameters of diamond tool were designed according to the influence of tool geometric parameters on the processing.Diamond tool blanks were obtained by material selection,orientation,cutting and brazing.Secondly,according to the interaction between the diamond particles with the diamond surface and the scaife during the lapping process,the lapping process of the diamond surface was analyzed.The effects of scaife,scaife rotation speed and crystal orientation on the accuracy of the diamond surface were studied experimentally.After lapped the surface roughness of diamond is less than 1nm.Then based on the geometrical characteristics of the flank of the arc-edge diamond tool,the surface equations of the conical and cylindrical flank were solved,the curve equation of diamond tool edge was obtained,then the forming principle of the flank of the diamond tool was studied.The conical and cylindrical flank faces were lapped by a diamond tool lapping machine.The flank face of the obtained tool was tested by a profilometer and an interferometer,after lapped,the P-V value of the contour error of the diamond tool flank is about 0.05?m,Ra is about 0.01?m,and the surface roughness of the flank is about 1nm.Finally,the lapping direction of diamond tool rake face was analyzed.By used the curve equation of the edge contour,the standard aspheric surface equation of the edge contour curve was obtained,a new method for measuring the edge contour error of arc-edge diamond tool with profilometer was proposed.the contour error of the lapped tool is 0.025?m in the range of 67°.Ultra-precision machining of zinc selenide spherical surface and aluminium surface was realized by using the arc-edge diamond tools obtained after lapping,the usability of the tools was verified.