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

• We developed a technique for precision conditioning coarse-grained diamond wheels.
• The conditioned wheels are with wheel run-out errors less than 2 μm.
• The conditioned wheels are also with constant grain peripheral envelopes.
• As well as the flattened diamond grain tops with certain protrusion height.
• They have potential application in ultraprecision grinding hard-to-machine materials.

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 15 μm (D15) and 91 μm (D91), respectively, as conditioners for truing of diamond wheels with grain sizes of 46 μm (D46), 91 μm (D91) and 151 μm (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 <2.5 μm, which is a prerequisite for introducing coarse-grained diamond wheels into ultra-precision machining of brittle and hard-to-machine materials.