The minimum quantity of lubricant technique in grinding of steel using a wheel cleaning system

The application of minimum quantity of lubricant (MQL) for metal cutting has emerged as an alternative for reducing the abundant flow of cutting fluids, thus achieving cleaner production. Although considered an innovative technique in grinding operations, the widespread application is hindered mainly due to the high heat generation and the clogging of wheel pores caused by machined chips, harming the final product quality and increasing tool wear. This study sought to improve MQL use in grinding. Thus, besides the conventional MQL injected at the wheel/workpiece interface, a compressed air jet was also added, in order to clean the clogged wheel pores from the mixture of MQL oil and machined chips. Experiments were conducted using external cylindrical plunge grinding on AISI 4340 quenched and tempered steel, and a vitrified cubic boron nitrite (CBN) wheel. The lubri-refrigeration methods employed were the conventional with abundant flow, conventional MQL (both without any cleaning air jets) and MQL with the cleaning jet, directed at the surface at different angles of incidence. The main goal of these experiments was to verify the viability of replacing traditional abundance flow with MQL with wheel cleaning. The analyses were conducted by measuring the following output variables of the process: workpiece surface roughness, roundness, diametrical wear of the wheel. Results show the possibility of implementing the cleaning jet technique as a technological improvement of the minimum quantity of and grinding, in order to reduce the usage of cutting fluids. The MQL technique with cleaning compressed air jet, for a specific angle of incidence (30°) proved to be extremely efficient to obtain improved surface quality and accurate workpiece shape, as well as to reduce wear wheel and to prevent thermal damage, when compared to the other lubri-refrigeration methods tested (without cleaning jet).Special thanks to FAPESP (State of São Paulo Research Assistance Foundation) (process 2009/51440-5 (Research Assistance) and 2009/51439-7 (Scientific Initiation)) for the financial resources made available for this study, and to the Schaeffler Group (INA brand) for the support offered in conducting metallographic analyses