Effects of minimum quantity lubrication by vegetable oil-based cutting fluid on machinability of steel

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 cutting fluid also leads to economical benefits by way of saving lubricant costs and workpiece/tool/machine cleaning cycle time. Significant progress has been made in dry and semidry machining recently, and minimum quantity lubrication (Mal) machining in particular has been accepted as a successful semidry application because of its environmentally friendly characteristics. A number of studies have shown that Mal machining can show satisfactory performance in practical machining operations. However, there has been little investigation of the cutting fluids to be used in Mal machining. In this regard the proposed research work has been carried out with a view to study the effects of minimum quantity lubrication (Mal) by vegetable oil-based cutting fluid on the cutting performance of AISI x 9310 steel, as compared to completely dry and wet machining in terms of chiptool interface temperature and tool wear reduction, tool life increment and machined surface protection. An approach based on the process parameters (speeds, feeds and depth of cut) has also been performed to identify the suitable MQl nozzle position for better cooling action. In the study, the minimum quantity lubrication will be provided with a spray of air and vegetable oil. Compared to the dry or wet machining, MQl machining performed much superior mainly due to substantial reduction in cutting zone temperature enabling favorable chip formation and chip-tool interaction. It also provides substantial reduction in tool wear, which enhanced the tool life, and surface finish. Furthermore, it provides environment friendliness (maintaining neat, clean and dry working area, avoiding inconvenience and health hazards due to heat, smoke, fumes, gases etc. and preventing pollution of the surroundings) and improves the machinability characteristics.