On-machine dry electric discharge truing of diamond wheels for micro-structured surfaces grinding

Abstract

Precision grinding with diamond wheels gives a promising alternative to achieve high quality micro-structured surfaces on optical molds. However, it is difficult to true these diamond wheels efficiently, because of the remarkable resistance property and the geometrical limitation of small wheel profile. In this paper, an on-machine dry-EDT method to precision shape and prepare diamond wheels with various profiles was proposed for micro-structured surface grinding. Firstly, the fundamental truing errors were analyzed based on the dry-EDT kinematics. And then the capabilities of dry-EDT truing for high abrasive concentration metal bonded diamond wheels were presented. Next, the effects of kinematic parameters variables on trued wheel profile accuracy were investigated. Finally, the micro-structured surfaces on SiC ceramic and tungsten carbide WC were ground by these trued diamond wheels. The experiments results showed that the arc-shaped diamond wheel (diameter of 200mm) with 4μm profile error (PV) and 1.0023mm profile radius, and the V-shaped diamond wheel with 22.5μm V-tip radius and 120.03° profile angle could be obtained by on-machine dry EDT. The kinematic parameters of dry-EDT have an important influence on truing profile accuracy of diamond wheels, especially for the tip of V-shaped wheel. The subsequent grinding show that the edge radius of V groove array on SiC is less than 2μm, while the radius of included corner is around 55μm. The PV error of ground arc groove array on WC is less than 5μm. The surface roughness of ground micro-structured surface Ra is 142nm and 97nm for SiC and WC, respectively.