Study On The Surface Quality Analysis And Process Parameter Optimization Of KDP Crystal Single Point Diamond Cutting

KDP crystal is a kind of non-linear optical material with excellent properties,which has been widely used with the invention and development of high power lasers in the 1940 s.Because of its great development prospects in the field of optical application,it has become a research hotspot that countries are competing to invest tremendous human and material resources.However,the physical properties of KDP crystal,such as soft texture,high brittleness,easy deliquescence,material anisotropy and sensitivity to temperature change,make it very easy to produce surface defects such as pits and cracks during single point diamond cutting.As a result,KDP crystal parts are easily damaged by laser at surface defects,which seriously affects the service life of the laser.Therefore,it is of great significance to study the surface quality analysis and process parameters optimization of KDP single point diamond cutting.In order to improve the surface quality of single point diamond cutting of KDP crystal,the basic unit and ideal configuration of KDP crystal are defined from the microscopic structure of KDP crystal,and the anisotropic distribution of anisotropic elastic modulus and shear modulus of common crystal plane are deduced.It lays a theoretical foundation for exploring the internal relationship between the optimal processing orientation of materials and the distribution law of mechanical properties of materials.Secondly,through ABAQUS finite element software,the physical model of KDP crystal cutting simulation model,especially the method of establishing and assigning anisotropic properties of materials,is introduced in detail.Aiming at the KDP crystal processing process,the right angle cutting model,the end cutting model and the flying cutter cutting model are established respectively.Through the above finite element model,the effects of tool geometry angle and cutting parameters on chip formation process,cutting force and final surface quality are explored.Finally,through the orthogonal test method,the experimental design of ultra-precision cutting of KDP crystal is carried out,and then the experimental results are correlated and analyzed to explore the mathematical statistical law hidden behind the randomness,and the prediction model of the influence factors on the surface roughness and quality distribution of single-point diamond cutting KDP crystal is established.Through the design of special fixture device,the intermittent cutting mode of flying cutter is simulated in general single point diamond lathe,and the cutting process of KDP crystal along a certain orientation is realized.The optimum processing orientation of the highest surface quality is obtained by the analysis of experimental data.The results of FEM simulation and technological experiments show that negativerake angle cutting in single-point diamond cutting has some shortcomings,such as large cutting force and difficult chip removal,but it is beneficial to enhance the plastic processing ability of brittle KDP crystal.The processing parameters of KDP crystal were optimized by technological experiments.The optimal combination was spindle speed 1000 r/min,feed speed 5 r/min,cutting depth 2 um,tool rake angle-25o,and the surface roughness was 5.0 nm.The results of flying cutting experiment,end turning experiment and mechanical anisotropy of KDP crystal show that cutting KDP crystal along the direction of smaller elastic modulus and larger shear modulus can obtain higher surface processing quality.