Electromechanical system in ultra-precision cutting machine tool and its application in processing of Fresnel lens mold

For processing micro groove Fresnel lens mold, the cutting technology and electromechanical system of an ultra precision cutting machine tool with a B rotary axis were designed. Mechanical modules of the machine tool were presented, and a motor drive and an encoder feedback system were designed. By applying linear motor direct drive, the Heidaenhain nano-scale linear encoder signal subdivided by the motor driver was used for closed-loop feedback. Electric control system of the ultra precision cutting machine tool was designed, of which the NC system was open whole soft type PA NC. The straightness error of a guide is 0.15 μm/200 m. For the B rotary axis, its positioning accuracy is 3″, and the rotary displacement resolution is 0.036″. In the cutting experiments, flat surface (Ф280 mm), semi-sphere (Ф100 mm), complex curved surface was machined. And the Fresnel lens mold was processed by the method of rotary B-axis. The experiments show that the surface roughness R_a of flat surface is 5 nm, and the surface roughness R_a of Fresnel lens mold is 7.3 nm. The results show that it is feasible that the process technology of Fresnel lens mold is based on the high precision rotary B-axis.