Proceedings of the 12th euspen International Conference vol:12 pages:225-229
12th International Conference of the European Society for Precision Engineering & Nanotechnology edition:12 location:Stockholm date:04-08 June 2012
Metal-bonded wheels have a few advantages over normal grinding wheels, including higher stiffness, better thermal conductivity for removing process heat and high tool durability. This means grinding of hard materials like ceramics can be done more accurately; the tool life is longer; reshaping of the tool is delayed; and higher G-ratios can be achieved. To keep the super-abrasive metal-bonded grinding wheels sharp and to ground mirror-like surfaces, in ELID-grinding the wheels are dressed continuously and in-process through electrolytic passivation. An electric current between the anodic wheel and an external electrode can lead to the formation of an insulating layer covering the wheel. The goal of this study is to investigate the fundamentals in the growth of the layer in order to have a better understanding in the process. By analyzing the evolution of the voltage and current pulses generated by the power supply (Fuji ELIDER ED921) the layer growth can be monitored. At the start of pre-dressing, the cast iron bond (CIB) is purely metallic. The impedance of the electrolytic cell has a high capacitance and a small resistance. The current dissolves the iron which is then recombined with oxidizers of the electrolyte to form dense and insulating hydroxides. Measurements of the passivation layer resistance for different parameter settings show a steady rise until the insulation is completed. The results for different parameter settings are consistent with Faraday‟s law which states that the accumulated charge governs the layer growth. From these experiments an equivalent electrical model is derived.