金刚石砂轮金属结合剂的气中单脉冲电火花放电去除机理

针对金属结合剂金刚石砂轮修锐困难的问题，提出采用气中电火花接触放电修锐的方法。为有效地实现微细金刚石砂轮的修锐，建立单脉冲电火花放电去除加工的试验系统，研究金属结合剂的气中和液中电火花放电去除机理。在试验研究中，主要分析无负荷电压和放电极性对脉冲放电电流、脉冲放电间隙、脉冲放电去除量、电极磨耗比等的影响。结果表明，正极性不易发生短路现象，而且气中的脉冲放电间隙小于液中的 ，适应于微细金刚石砂轮的修锐。此外，在气中放电中存在由绝缘破坏引起的火花放电向附有电弧柱的电弧放电转变的临界无负荷电压，且电火花放电的去除量可以明显小于电弧放电的去除量，但是当无负荷电压小于某一定值时电极消耗比会快速增加。修锐的试验结果显示，利用气中单脉冲电火花放电去除加工条件可以实现金属结合剂微细金刚石砂轮的修锐，产生较好的砂轮出刃形貌，改善磨削表面质量。

MECHANISM ON DRY IMPULSE DISCHARGE REMOVAL OF METAL BOND OF DIAMOND GRINDING WHEEL

Due to the difficulty of dressing of metal-bonded diamond grinding wheel, dry electro-contact discharge dressing is employed. In order to realize dressing of fine diamond grinding wheel effectively, removal behavior of metal bond for dry and wet coolants is investigated. In experimental study, dry impulse discharge machining experiment system is established to investigate effect of open-circuit voltage and discharge polarity on impulse discharge current, discharge duration, discharge gap, discharge removal, electrode wear ratio, etc. The results show that straight polarity does not produce electrode material adhered to machined surface and the dry discharge gap is 2～3 times less than the wet, which is suitable for dressing of fine diamond grinding wheel. In addition, there exists a critical open-circuit voltage from which spark discharge aroused by insulation breakdown is transferred to arc discharge companied with an arc pillar. Although the discharge removal of spark discharge may be much less than that of arc discharge, the elec-trode wear increases greatly when open-circuit voltage is less than certain value. It is confirmed that the results of impulse discharge machining experiment may be applicable to dry electro-contact discharge dressing of fine diamond grinding wheel, resulting in good wheel topography and improving ground surface.