A novel ultrasonic-assisted dressing method of electroplated grinding wheels via stationary diamond dresser

摘要

To achieve fine surface roughness, tungsten carbides are mostly ground with resin or vitrified bonded diamond wheels. The use of cost-effective electroplated diamond tools (single layer) is, despite some specific improvements, such as geometrical flexibility, excellent profile holding, large chip spaces and good cooling characteristics, which allows even dry grinding processes, unusual when fine surface roughness is desired. It is generally due to the high grain protrusion (approx. 40 % compared to approx. 15 % with resin bonded or vitrified diamond wheels) which leads to the induced grooves on the ground surface combined with high surface roughness. Another disadvantage of single-layer bonded grinding wheels is their low range of dress ability. This article describes a possibility to overcome the drawbacks of the electroplated diamond wheels by ultrasonic-assisted fracturing of the diamond grains. For this purpose, an ultrasonic-assisted stationary dresser is used. The ultrasonic unit generates hits on the diamond grains. The grinding wheel rotates with a very slow circumferential speed, which is uncommon in conventional dressing methods, so that the grains are fractured by the oscillating movement of the dresser. However, numerous sharp cutting edges are generated due to the generated hits. This method allows the generation of cutting edges on relatively course grain sizes (in this case, D251) that have the properties of smaller grain sizes, and therefore, surfaces with lower roughness values are produced while the advantages of the electroplated grinding wheels, such as good profile keeping and good cooling characteristic, are maintained. Additionally, the service life of the electroplated wheel can be increased and the grinding parameters can be kept nearly constant. Experimental analyses have shown that the grinding of tungsten carbide with fractured electroplated D251 diamonds enables fine surface roughness from Ra < 0.1 mu m and Rz < 0.8 mu m.