An experimental investigation of the effects of workpiece and grinding parameters on minimum quantity lubrication—MQL grinding

Abstract

Coolant is a term generally used to describe grinding fluids used for cooling and lubricating in grinding process. The main purposes of a grinding fluid can be categorized into lubrication, cooling, transportation of chips, cleaning of the grinding wheel and minimizing the corrosion. On the other hand, grinding fluids have negative influences on the working environment in terms of the health of the machine operator, pollution and the possibility of explosion (for oil). Furthermore, the cost of the grinding fluid, filtering and waste disposal of the metal working fluids is even higher than the tool cost and constitutes a great part of the total cost. Additionally, grinding fluids can not effectively penetrate into the contact zone, are health hazard and their consumption must be restricted. Generally, compared to other machining processes, grinding involves high specific energy. Major fraction of this energy is changed into heat, which makes harmful effect on the surface quality as well as the tool wear. Since there is no coolant lubricant to transfer the heat from the contact zone in dry grinding, surface damages are not preventable. Alternatives to current practices are getting more serious consideration in response to environmental and operational cost pressures. One attractive alternative is the minimum quantity lubrication (MQL) grinding or the near dry grinding (NDG). In near dry grinding an air–oil mixture called an aerosol is fed into the wheel-work contact zone. Compared to dry grinding, MQL grinding substantially enhances cutting performance in terms of increasing wheel life and improving the quality of the ground parts. In this research, the influences of workpiece hardness and grinding parameters including wheel speed, feed rate and depth of cut have been studied on the basis of the grinding forces and surface quality properties to develop optimum grinding performances such as cooling, lubrication, high ecological and environmental safety.