Influence of the heat deformation of ultra-precision fly cutting tools on KDP crystal surface microstructure

Cutting tools may heat up during use, causing them to deform. Such an effect degrades the surface microstructure of potassium dihydrogen phosphate (KDP) crystals via ultra-precision fly cutting. In this process, thermal expansion of the tool displaces the tool tip perpendicular to the workpiece processing surface. Such displacement is difficult to measure experimentally due to the limited sensitivity of displacement sensors and the severe conditions present during cutting processes. In this study, a cutting surface simulation model based on machine kinematics of the fly cutting and a thermal model based on the experimental results of the principal cutting forces are established in KDP crystal ultra-precision flying cutting to explore the specific impact on the workpiece due to the thermal deformation of the tool. The relationships between cutting parameters and principal cutting forces are thereby determined. The relationships between tip heat inflow, tip displacement perpendicular to the workpiece processing surface, and crystal surface microstructure were simulated. The results demonstrate that the heat deformation of the tool slightly influences the roughness and waviness of KDP crystal surfaces, and increases their surface slope, thus influencing surface precision. This directly affects the optical performance of such crystals.