Modelling and Optimization of Cutting Strategy and Surface Generation in Ultra-precision Raster Milling

Ultra-precision raster milling (UPRM) is an advanced manufacturing technology for the fabrication of non-symmetric freeform surfaces. The surface generation is very dependent on cutting strategies and more factors affect surface quality in UPRM, as compared with ultra-precision diamond turning and conventional milling. In this research, theoretical and experimental investigations are conducted to study the effect of cutting strategy on surface generation in UPRM. The influences of shift length and tool-interference are firstly introduced into surface generation in UPRM. A three-dimensional (3D) holistic kinematic roughness prediction model is developed and makes more precise predictions than the existing models.;According to the investigation on influences of cutting strategy and machine characteristics on surface quality and machining efficiency in freeform machining, two methodologies of cutting strategy optimization are proposed for UPRM: quality-optimal and time-optimal strategies. The developed optimal cutting strategies consider the geometry of freeform surfaces, the cutting mechanics and surface generation mechanism of raster milling.;The influences of material swelling and elastic recovery on chip formation and surface generation in UPRM are investigated in this study. A surface roughness prediction model is built by adding the material elastic recovery effect and provides more precise predictions than the kinematic model. A new method is proposed to characterize the effect of material properties on surface finish, which successfully separates the effect of cutting strategy on surface roughness from the material effect.;The originality and significance of the thesis include: (i) the successful development of a surface roughness prediction model provides a quantitative relationship between cutting strategy and surface roughness in UPRM; (ii) the cutting strategy optimization methodologies are developed to optimize cutting parameters and TPG to achieve ultra-precision freeform surfaces in an efficient way; (iii) a deterministic roughness prediction model that accounts for material elastic recovery on surface generation in UPRM has been developed and (iv) a new method is proposed to characterize the extent of the material induced distortion of the cutting profile. This study provides an important means for a better understanding of the surface generation mechanism in UPRM and contributes significantly to the further improvement of the performance of ultra-precision machines.