Effect of machining parameters on surface finish and subsurface damage for diamond-turned germanium

Abstract

Germanium lenses are widely used in various scientific and technological applications mainly infrared optical components. The performance of these lenses depends upon the surface finish, which is challenging to achieve during ductile-regime machining. It is crucial to provide the optimum parameters to ensure the high-quality surface, without surface and subsurface damage. In the present work, an attempt has been made to analyse the effect of input machining parameters on surface finish and subsurface damage distribution, induced during the diamond turning. Taguchi’s optimization has been performed to optimize the parameters affecting the performance and surface quality of fabricated components. Abbott–Firestone (A–F) curve is utilized to study the distribution of peaks and valleys on the machined surface. Additionally, chip morphology and machining forces are analysed to study the material removal behaviour at varying parameters. Further, indentations are performed on the best and worst combinations to examine the effect of parameters selection on surface cracks propagation. It is found that surface with a greater number of valleys leads to chipping during indentation. In this study, a surface roughness of 2.3 nm is achieved with minimum subsurface deformation.