Modeling of Ultra-precision Raster Milling and Characterization of Optical Freeform Surfaces

Ultra-precision raster milling is an enabling technology for machining freeform optical surfaces with sub-micrometric form accuracy and nanometric surface finish without the need for any subsequent post processing. Due to the geometrical complexity of the surfaces, there is still a lack of surface characterization methods to measure the ultra-precision freeform surfaces. There is a need for the development of theoretical models and systems to predict and simulate the surface generation in the ultra-precision raster milling as well as to characterize optical freeform surfaces.;The research work has been divided into three parts. The first part consists of a theoretical and experimental investigation of the factors affecting the surface roughness in ultra-precision raster milling. Various surface roughness models have been built and were experimentally verified through a series of cutting experiments.;In the second part, a series of novel methods and surface characterization systems have been established for the measurement and form characterization of ultra-precision freeform surfaces. They include the Integrated Freeform Characterization Method, the Robust Freeform Characterization Method, the Coupled Reference Data Freeform Evaluation Method, and the Hybrid Fitting and Matching Method. They have been verified through a series of computer simulations and measurement experiments. The results indicate that the developed freeform surface characterization methods and systems can realize precise measurement and characterization of ultra-precision freeform surfaces with form accuracy down to the sub-micrometer range.;A model-based simulation system has been presented for the prediction and optimization of form generation in ultra-precision raster milling in the third part of the study. The system takes into account different factors which affect the surface generation such as the cutting mechanisms, tool path and the cutting process. The performance of the system has been successfully verified through a series of cutting experiments on different freeform surfaces. The successful development of the analytical models and the model-based simulation system helps to make the ultra-precision raster milling process more predictive, and also allows the surface generation and cutting strategies to be optimized without the need for conducting expensive and time consuming trial-and-error cutting tests.