Cylindrical Wire Electrical Discharge Truing of Metal Bond Diamond Grinding Wheels

Abstract

The goal of this research was to use the wire Electrical Discharge Machining (EDM) to profile a metal bond diamond grinding wheel, and then study the wear and grinding performance of the EDM trued wheel. Diamond wheels are known to exhibit low wheel wear for precision grinding of ceramics but create difficulty in creating precision trued forms. With the increased use of hard engineering ceramics in mechanical design, new methods of truing these wheels had to be investigated. In profiling a vitrified bond diamond wheel, a Computer Numerically Controlled (CNC) single point diamond or a diamond crush roll is often used. However, due to the high strength of the metal bond matrix, these methods cannot be implemented with a metal bond diamond wheel. Instead of applying a mechanical force, Wire Electrical Discharge Truing (WEDT) process utilizes electrical sparks to erode the metal matrix, which allows the non-conductive diamonds to simply fall away. A precision spindle was first built to rotate the wheel inside a traditional wire EDM machine. Once the process proved feasible, grinding studies were developed to compare the performance of a WEDT wheel against a diamond rotary trued/stick dressed wheel. Grinding force, surface finish of the ground silicon nitride parts, and wheel wear were all examined. The surfaces of both truing methods were compared using Stereo-Scanning Electron Microscopy to measure the protruding diamonds' height and identify the wear mechanism. Result of the research shows promise for the future use of WEDT as a truing method for metal bond wheels.