Modelling and Optimization of Cutting Strategy on Freeform Machining in Ultra-precision Raster Milling

This chapter provides a new methodology for the integrated optimization of cutting parameters and tool path generation (TPG) based on the development of prediction models for surface roughness and machining time in ultra-precision raster milling (UPRM) or fly cutting. The proposed methodology simultaneously optimizes the cutting feed rate, the path-interval, and the entry distance in the feed direction to achieve the best surface quality in a given machining time. Cutting tests are designed to verify the integrated optimization methodology. The experimental results show that, in the fabrication of plane surface, the changing of entry distance improves surface finishing about 40 nm (Ra) and 200 nm (Rt) in vertical cutting and decreases about 8 nm (Ra) and 35 nm (Rt) in horizontal cutting with less than 2 s spending extra machining time. The optimal shift ratio decreases surface roughness about 7 nm (Ra) and 26 nm (Rt) in the fabrication of cylinder surfaces, while the total machining time only increases 2.5 s. This infers that the integrated optimization methodology contributes to improve surface quality without decreasing the machining efficiency in ultra-precision milling process.