Comparison of minimum quantity lubrication (MQL) grinding with wet and dry grinding

Abstract

Minimum quantity lubrication refers to the use of cutting fluids of only a minute amount-typically of a flow rate of 50 to 500 ml/hour-which is about three to four orders of magnitude lower than the amount commonly used in flood cooling condition, where, for example, up to 10 liters of fluid can be dispensed per minute. The concept of minimum quantity lubrication, sometimes referred to as near dry lubrication or micro lubrication, has been suggested since a decade ago as a means of addressing the issues of environmental intrusiveness and occupational hazards associated with the airborne culling fluid particles on factory shop floors. The minimization of culling fluid also leads to economical benefits by way of saving lubricant costs and workpiece/tool/machine cleaning cycle time. The aim of the present work is primarily to explore and evaluate the role of MOL on grindability characteristics of some commonly used steels mainly in terms of chip formation mode, grinding temperature and surface roughness which govern the productivity, product quality and overall efficiency. Considering the chip characteristics in dry and wet grinding, the mechanism of chip formation is mainly due to shearing, ploughing and rubbing. But in MOL substantially changed in mechanism of material removal to predominantly shearing. It is also evident that the mechanism of chip formation shift further from shearing to fracturing with increase in work hardness. Grinding zone temperature is reduced more in MOL compared to dry and wet grinding. In MOL, surface roughness is lower than wet grinding but higher than dry grinding. But plastic deformation, surface and subsurface cracks are significant in dry grinding compared to MOL grinding. Thus MOL improves the grindability characteristics.