However, there has been little research on discharge dressing of a coarse diamond grinding wheel. The previous studies showed that highly efficient dressing of fine-grained diamond grinding wheel can be achieved by using impulse electrical discharge and on-line electrolytic dressing methods. Although the laser dressing method could make the diamond grains quickly protrude from the metal bond surface of the grinding wheel, the high energy beam would also ablate the diamond grains, which was not conducive to grinding. Besides, the dressing and truing efficiency was extremely low. It is very difficult to dress and true the coarse diamond grinding wheel using the traditional mechanical dressing and truing method. The influences of feed speed and wheel speed on grinding force ratio were more significant, but the influence of depth of cut was little.

In order to achieve highly efficient ground quality of sapphire glass, the depth of cut was controlled within 7 µm, and the wheel speed and feed speed were 3000–5000 r/min and 10–20 mm/min, respectively. The minimum line roughness R a and surface roughness S a of ground sapphire glass surface were 0.194 µm and 0.736 µm, respectively. The experimental results show that the grain protrusion height on the surface of a coarse diamond grinding wheel dressed by dry electrical discharge can reach 168.5 µm. The influences of grinding process parameters such as wheel speed, depth of cut and feed speed on the ground surface quality, grinding force and grinding force ratio on sapphire glass were investigated, and the relationship between grinding force and ground surface quality was also revealed.

The dry electrical discharge dressing technology was employed to obtain high grain protrusion and sharp micro-grain cutting edges. In this paper, in view of low grinding efficiency and poor ground surface quality of sapphire glass, the coarse diamond grinding wheel dressed by dry impulse electrical discharge was proposed to perform efficient and precise grinding machining of sapphire glass.

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