Precision Deterministic Machining of Polymethyl Methacrylate by Single-Point Diamond Turning

Abstract

Polymethyl methacrylate (PMMA) is widely used as substrate material for optical fabrication in infrared and visual applications. The single-point diamond turning (SPDT) being one of the deterministic precision machining technologies needs to be explored for the manufacturing of the optical components as it is capable of providing the required characteristics such as accuracy, quality, and repeatability. Therefore, it becomes imperative to study the role of influential factors in affecting the machining characteristics of PMMA. The present work is an experimental outcome of precision deterministic machining of PMMA with SPDT. The five input factors of depth of cut, tool overhang, tool nose radius, rotational speed of spindle, and cutting feed rate are considered for machining a flat profile. Surface roughness (Ra), waviness error (Wa), and profile error (Pt) are three output parameters. The process is optimized individually for Ra, Wa, and Pt by Taguchi method. Subsequently, Ra, Wa, and Pt are optimized simultaneously by grey relation to obtain an optimal solution which identifies rotational speed of the spindle, depth of cut, and cutting feed rate as significant parameters. Ra as 11.9 nm, Wa as 0.0289 µm, and Pt as 0.285 µm are obtained as minimum values. Effect of coolant on transmission of light is also studied.