Cutting forces in ultraprecision machining freeform optics: Analysis through virtual simulations and experiments

Abstract

In ultraprecision manufacturing of freeform surfaced optics and devices, the ultraprecision diamond turning process holds a significant importance. However, high costs, quality assurance and long machining times are inevitable challenges in ultraprecision manufacturing. This scientific talk presents the concept of a virtual lens model based on the requirement of ‘deterministic manufacturing’ in the ultraprecision machining process, while enabled by scientific understanding of micro cutting mechanics and its applicational affect. By analysis of the freeform surface modelling and machining toolpaths and underlying micro cutting mechanics, this research aims to define surface quality and its optical performance prior to the machining process. The research further delves into cutting force modelling and 3D surface parameters to analyze the machining toolpath, and virtual simulations and experiments are conducted. The simulations and experiments are focused on verifying the correlations between the surface characteristics, such as surface roughness, peak valley distance and most importantly, surface texture aspect ratio, and the optical performance of the freeform surface. The analysis of surface texture formation and cutting forces modelling are essential for the simulation development and experimental design. The cutting forces modelling integrates the Akins' model with the influence of continuously varying shear angles on the freeform surface. Toolpath data from the cutting process is used to meticulously analyze depth-of-cut (DoC), curvature variations, and shear angle variations throughout the process, and thus to enable the consistent surface texture aspect ratio at the surface generation as desired.