Capillary penetration mechanism and machining characteristics of lubricant droplets in electrostatic minimum quantity lubrication (EMQL) grinding

In this work, the machining performance of an electrostatic minimum quantity lubrication (EMQL) technology in grinding of Cr12 die steel was systematically investigated in terms of grinding temperature and forces and grinding ratio, as well as surface quality and microstructures. The intensity of charging voltage was varied in order to obtain an optimal grinding performance. A model of capillary penetration of lubricant droplets to the abrasive-workpiece interface was proposed to reveal the lubrication mechanism of EMQL. It was found that EMQL at an electrostatic voltage of 4 kV significantly reduced the grinding forces and surface roughness, but increased the grinding ratio by 24.8% in comparison with a conventional MQL technology. The improved performance was attributed to the fact that EMQL promoted the penetration of lubricant droplets, achieving a better interfacial lubrication with low friction and grinding heat. The EMQL was also believed to reduce the surface micro-hardness of workpiece materials by enhancing the migration of dislocations, hence improving the cutting effect of abrasive grains.