Thermal and Structural Deformations During Diamond Turning of Rotationally Symmetric Structured Surfaces

Abstract

Diamond turning of microstructures on the surface of large cylindrical workpieces has become important with advances made in roll-to-roll manufacturing processes of optical films, drag reduction films, microfluidic devices, and organic electronic components. Micromachined cylindrical workpieces are used as production masters in various printing, embossing, and coating processes. The microstructures machined in this study were 18μm in height and had a pitch of 35μm. These dimensions required control of the location of the single crystal diamond cutting tool that was used for machining to submicrometer levels. The significant error sources identified in the machining process were thermal effects and deflections of the structural loop of the diamond turning machine (DTM) that led to registration errors of the cutting tool between consecutive passes. Environmental temperature variation errors (ETVEs) were measured and modeled as a function of long-term ambient temperature fluctuations. Also studied was the mechanical compliance of the structural loop of the DTM. The height adjustable tool stack and aerostatic spindle were identified as the most compliant components. The cutting forces for radius and V-shaped diamond cutting tools at various depths of cut were measured using the known compliance of the aerostatic bearing to predict workpiece deflections.