Influence of cutting parameters on system vibration and optical performance of diamond turned optics

In this paper the influence of vibration on reflectivity is systematically analyzed. A three-dimensional topography model of a machined surface considering vibration is established first. Based on the three-dimensional morphology model, the reflectivity of a diamond turned surface is calculated by a rigorous coupled wave method. The influences of cutting parameters on the diffraction effect of a diamond turned surface are discussed. The predicted and experimental results reveal that as the vibration intensifies with an increase in cutting depth and feed rate, the peak-valley (PV) roughness of the machined surface increases, which yields an increasing diffraction effect, i.e., resulting in a decrease in reflectivity. When the spindle speed is low, the tool and workpiece have a small sliding velocity, causing a great deal of friction, which amplifies the deformation of the workpiece surface. In this case, the PV value of the machined surface roughness is large, leading to a greater diffraction effect and bad reflectivity. With the increment of spindle rotation speed, the friction is relieved quickly, but the vibration is intensified, which produces increasing reflectivity. When the spindle speed is set to about 1200r/min, the reflectivity reaches the maximum value. When the spindle speed is larger than 1200r/min, the increase of vibration is dominant, resulting in a gradual increase in PV surface roughness and a decrease in reflectivity.