Influence of Solid Contaminants in Metal Working Fluids on the Grinding Process

Abstract

Metal working fluids (MWF) are widely used in grinding processes to lubricate and to remove the heat and chips from the contact zone. Apart from the chips, abrasive particles from the worn grinding wheel contaminate the metalworking fluid. The solid contaminants, in particular the abrasive particles crumbled from the grinding wheel, are believed to cause several negative effects like for example damaging the guideways of the machine tool. Furthermore, it is assumed that a pronounced interaction of the solid particles and the machined surface will decrease the achievable surface quality of the ground surfaces. Cleaning units are employed within the fluid circuit to prevent failure of the machine tool and to ensure the desired surface quality. The economic efficiency of such cleaning plants cleaning plants depends strongly on the choice of the grade of filtration (the particle size which has to be retained). A grade of filtration which exceeds the actual needs of the machining process adds unnecessary costs for operating the cleaning unit. To enable cost efficient design of filtration units the interaction between solid contaminants and the machining process has to be understood. The results of grinding experiments (face grinding of workpieces made of AISI 52100) confirm a significant increase of the surface waviness when corundum particles are added to the MWF. The underlying effect is an extraordinary tool wear combined with a locally varying effective depth of cut. The excess particles block the pores of the grinding wheel and are transported into the grinding gap. An increasing ratio of the size of solid contaminants and the size of the bonded grains on the wheel accelerates the wear of the tool.