Tool path generation for machining of optical freeform surfaces by an ultra-precision multiaxis machine tool

Optical freeform surfaces are crucial to the development of complex and optical-electromechanical devices used in many photonics products. The fabrication of high-quality freeform lens is based on ultra-precision freeform machining technology which allows direct machining of freeform surfaces with submicrometric form accuracy and nanometric surface finish. In this paper, the application of ultra-precision freeform machining to the fabrication of an optical freeform surface is addressed. The methodology for the development of the tool path generator for a progressive lens is discussed. According to the model of the freeform surface, which is represented by a double cubic B-spline surface, the method of changing parameters is used to calculate the numerically controlled (NC) machining tool path. The formula for calculating cutter location data, which considers the compensation of both the tool nose radius and tool swing radius of the fly cutter, is deduced. The cutting experiment of machining a freeform progressive optics lens by a multiaxis ultra-precision machine tool shows that the developed tool path generator can perform its function successfully.