A theoretical and experimental investigation into surface generation in ultra-precision diamond milling

Ultra-precision diamond milling (UPDM) provides a promising generation of high-quality surface up to sub-micrometric form accuracy and nanometric surface roughness. Prior to its machining process, the investigation on surface generation would be beneficial to achieve desired quality with reduced cost and boosted productivity. However, few studies discussed this issue so far. In this study, a theoretical and experimental investigation into surface generation was carried out in UPDM. Firstly, a geometric model was built up considering the material removal process between the milling tool and the workpiece. Secondly, surface generation process was elaborated according to the developed model. Finally, UPDM experiments were performed on a typical brass material at different cutting conditions and surface texture parameters were characterized according to ISO 25178-2. Autocorrelation function (ACF) analysis was employed for a detailed evaluation of surface generation. The results showed that the static factors (cutting parameters) as well as the dynamic factors (material effects and spindle vibration), which were associated with the cutting conditions, yielded a great influence on surface generation. Surface texture characterization indicated that there was a good consistence between simulation and experiment, demonstrating the feasibility of the proposed method. ACF analysis indicated that, with the increased feedrate/step ratio, surface generation approximately achieved a transition from the periodical surface (dominated by cutting residuals) to the random surface (determined by multiple components). Significantly, this study draws up a fundamental understanding toward surface generation in UPDM.