A variable-step-distance micro-milling repair cutter path generating method for damage points on a surface of an optical crystal related to a field of optical material and optical element surface repair and includes steps of establishing a mathematical model of a repair profile; determining discrete contact points between a cutter and the repair profile to obtain a cutter contact control point set by a GPR path generating method to control a movement trend of a pseudo-random path; interpolating the cutter position control point set into a spatial curve by a NURBS modeling method; creating a UG curve in a UG software according to the mathematical model, and using the UG curve as the repair path to perform a machining process simulation. The method has good elimination effects on cutter marks with constant period and improves the ability of the KDP crystal to resist strong laser damage.

The present invention is a method for slicing a workpiece, including: forming a wire row by a wire spirally wound between a plurality of wire guides and traveling in an axial direction, and pressing a workpiece against the wire row while supplying a processing liquid containing abrasive grains to a contact portion between the workpiece and the wire, wherein a used portion of the abrasive grains are subjected to a treatment with a mixed liquid of sulfuric acid and hydrogen peroxide, and the abrasive grains subjected to the treatment are reused for the slicing of a workpiece. This makes it possible to slice a workpiece with suppressing contamination of a wafer with metal impurities when abrasive grains are reused in slicing a workpiece by use of a wire saw.

The cutting method is a cutting method for cutting a workpiece using a wire tool, including: supplying a slurry containing abrasive grains having an electrical dielectric property to a region of the workpiece into which the wire tool cuts; generating an alternating electric field in a region between the wire tool and the workpiece; and running the wire tool along a direction in which the wire tool is drawn while the wire tool abuts on the workpiece.

Semiconductor wafers having a subsurface-referenced nanotopography of the upper side surface of less than 6 nm, expressed as a maximum peak-to-valley distance on a subsurface and referenced to subsurfaces with an area content of 25 mm25 mm, are produced from a workpiece by feeding the workpiece through a wire web tensioned between wire guide rollers and divided into wire groups, the wires producing kerfs as the wires engage the workpiece. For each of the wire groups, a placement error of the kerfs of the wire groups is used to compensate movements of the wires of the wire group as a function of the placement error, in a direction perpendicular to the running direction of the wires during feeding of the workpiece through the arrangement of wires, by activating at least one drive element.