An experimental study on discharge mediums used for electro-contact discharge dressing of metal-bonded diamond grinding wheel

Various discharge mediums such as Wet medium, Dry medium, impressed air and iron brush are proposed in electro-contact discharge dressing of metal-bonded #600 diamond grinding wheel. The aim is to understand how discharge mediums affect dressing behavior such as discharge gap, discharge removal and discharge current trace and dressing performance such as truing ratio of grinding wheel and surface roughness of workpiece, respectively. First, impulse electrical-discharge machining experiment was employed to investigate impulse discharge gap between metal-bond of grinding wheel and conductive-resin-bond of dresser and discharge removal of metal-bond for Dry medium and Wet medium, respectively. Then, electro-contact discharge dressing experiment was carried out to observe discharge current trace and truing ratio for various discharge mediums. Finally, grinding experiment was conducted to identify surface roughness of Al2O3 ceramics. It is indicated that Dry medium can produce narrower discharge gap and less discharge removal between grinding wheel and conductive dresser than Wet medium, which can be applied to stable dressing of finer diamond grinding wheel. In addition, impressed air used for discharge medium can produce the highest truing ratio, but resulting in the worst ground surface. It is also found that iron brush used for discharge medium can produce the best ground surface, but bringing the worst truing ratio. It is concluded that electro-contact discharge dressing is greatly dominated by discharge medium.