Design method for electrolytic machining cathode profile of all-metal petroleum screw drill stator

The invention belongs to the technical field of electrolytic machining, and particularly relates to a cathode profile design method for electrolytic machining of an all-metal petroleum screw drill stator. Designing the profile curve of the cathode profile into a dot matrix according to unequal gaps so as to obtain control points, orders and node vectors of the profile curve, constructing an operator, and controlling the global shape of the profile curve by using an integral spline operator so as to realize rough fitting of the cathode profile; when the integral of the square curvature of the cathode profile curve relative to the arc length of the cathode profile curve is minimum, the curvature of the curve is the most uniform, a cathode profile curve fitting index is constructed, discrete curvatures at all points of the cathode profile curve are calculated in sequence, accurate fitting of the cathode profile curve is achieved, and the error can be controlled within the precision range of 0.002 mm; and the cat