Ultra-precision grinding of optical glasses using mono-layer nickel electroplated coarse-grained diamond wheels. Part 1: ELID assisted precision conditioning of grinding wheels

Abstract

In order to realize ultra-precision grinding of optical glasses with mono-layer nickel electroplated coarse-grained diamond grinding wheels, a novel conditioning technique was developed using copper bonded diamond grinding wheels with grain sizes of 15μm (D15) and 91μm (D91), respectively, as conditioners for truing of diamond wheels with grain sizes of 46μm (D46), 91μm (D91) and 151μm (D151), respectively. During the conditioning process, the conditioners were continuously dressed by means of electrolytic in-process dressing (ELID). A force transducer was used to monitor the conditioning force while a coaxial optical distance measurement system was used to monitor the wheel run-out. In addition, a white-light interferometer (WLI) and a scanning electron microscope (SEM) were used to characterize the successively modified diamond grain morphologies of the conditioned wheels both directly and by a replication technique. The experimental results show that with optimized conditioning parameters, the developed conditioning technique can be applied for truing of coarse-grained diamond wheels within the abrasive layer achieving a constant wheel peripheral envelop surface exhibiting flattened diamond grains with a run-out <2.5μm, which is a prerequisite for introducing coarse-grained diamond wheels into ultra-precision machining of brittle and hard-to-machine materials.