Surface Quality Study Of Sapphire Crystal Grinded By Electrolytic In-Process Dressing (ELID) Method

The surface of sapphire crystal grinded under ductile mode was discussed with the Electrolytic In-Process Dressing(ELID) method in this paper. Different hardness materials, such as jade and glass ceramic, were also researched under ELID grinding. In this experiment, the ductile cutting mode of sapphire crystal has been achieved via changing the feed rate and the rotation speed of grinding wheel. All the sapphire crystal were grinded by ELID method on surface grinder that type is GM73-Ⅲand short cast iron fibers bonded diamond grinding wheel. Via grinding jade and glass ceramic with ELID method, the effect of feed rate and rotation speed to surface roughness had been researched. The surface profile, surface topography and manufacturing deficiency had been researched separately by using profilometer (XP-2TM), Atomic Force Microscope (AFM) and polarization microscope (DMRXP). Then the metamorphic layer was studied by grazing incidence X-ray diffraction method.The result showed that the surface roughness of sapphire crystal grinded by ELID method increases with the feed rate increasing, and the surface roughness decreases at first and then increaseswith the rotation speed increasing. There are two mode when the sapphire crystal was grinded, such as brittle fracture and ductile cutting. When the feed rate was 1μm and the rotation speed was 1900 rpm, the sapphire crystal was grinded under ductile cutting, the surface roughness of sapphire crystal was 3.2 nm. The manufacturing deficiency of sapphire crystal grinded by ELID method was reduced greatly compare to the surface grinded by traditional grinding method and polishing. The traditional grinding method and polishing was replaced by ELID method, and the efficiency also was improved. The thickness of metamorphic layer of sapphire crystal grinded by ELID is 2.33μm, which satisfied the request of sapphire crystal slice as functional material. After grinding the different hardness materials by ELID method, the direction that the surface roughness decreases at first and then increases when the rotation speed increases had been proved. And the corresponding rotation speed of the lowest surface roughness decreases withthe hardness increasing.