Yasuhiro Kamata

Analysis of Mist Flow in MQL Cutting

It is widely required not to use cutting oils containing surface reactive chlorine compounds in metal cutting for conservation of the global environment. Therefore, the minimal quantity lubrication (MQL) attracts attentions. In MQL machining, it is necessary to optimize the supply of oil mist so that the mist will concentrate near the tool tip for a better lubrication condition. The mist flow between the tool clearance faces and finished surfaces in MQL cutting was analyzed using a general purpose FEM software ANSYS/FLOTRAN. Through the analysis, the mist flow and pressure between the tool clearance faces and finished surfaces were visualized. Influences of the velocity and direction of the mist flow, and the cutting speed, on the amount of mist supplied to the space near the cutting edge were investigated quantitatively. Finally, optimal conditions of MQL were presented for the cutting process. Introduction Cutting oils are widely used for the disposal of chip, improvement of machining accuracy and surface roughness, and prolongation of tool life. These days, it is required to use chlorine-free cutting oils in machining for the conservation of the global environment. Disposal cost of the waste cutting oils is increasing. Regulations of use of the cutting oils are enforced. Therefore, from the environmental and economical points of view, minimal quantity lubrication (MQL) attracts attentions and has been investigated vigorously [1, 2, 3]. MQL machining that a small amount of vegetable oil or biodegradable synthetic ester (about 10 ml/h) is blown to the tool tip with compressed air is nearly equal to the traditional wet machining in tool life, efficiency of lubrication and surface roughness when appropriate conditions are selected in turning [4], milling [5], drilling [6] and tapping [7]. Cutting oil turns into mist in MQL machining. Therefore, it is necessary to investigate the flow of oil mist to concentrate it near the tool tip effectively. In this study, the optimization of MQL cutting-off was examined based on the analysis of mist flow. First, the analysis visualized the mist flow and pressure between the tool clearance faces and finished surfaces, and illustrated the influences of the mist blowing velocity, mist blowing angle and cutting speed on the amount of mist supplied to near the cutting edge quantitatively. Secondly, measurement of pressure distribution on the flank face when turning air blow off, proved that the suction generated near the cutting edge caused the mist flow to near the tool edge effectively. Finally, better conditions of MQL cutting-off were discussed. Three Dimensional Analysis of Mist Flow The mist flow between the tool clearance faces and finished surfaces in MQL cutting-off was analyzed under three-dimensional conditions using a FEM code ANSYS/FLOTRAN. The region of analysis and its finite element mesh are shown in Figs. 1 and 2, respectively; the clearance angle is 5 degrees, cutting width is 5 mm, the cross section of tool holder is 4 mm×25 mm and the depth of the groove is 5 mm. It is not necessary to take the rake angle and undeformed chip thickness into consideration. Because of the symmetry of the tool, only the half of the region is modeled with Key Engineering Materials Online: 2004-02-15 ISSN: 1662-9795, Vols. 257-258, pp 339-344 doi:10.4028/www.scientific.net/KEM.257-258.339

MQL Cutting of Inconel 718 with a Super Lattice Coating Tool

MQL (Minimum Quantity Lubrication) technology was applied to finish-turning of a nickel base superalloy, Inconel 718, with a PVD coated carbide tool with a super lattice coating of TiN/AlN. Cutting lubricant used for MQL was a biodegradable synthesis ester, which was supplied to the cutting point with compressed air from the both sides of flank and rake faces of the tool. At a cutting speed of 1.0 m/s and an air supply pressure of 0.4 MPa, MQL cutting showed longer tool life and better surface finish than both the dry cutting and wet cutting. When increasing the pressure of the air supply from 0.40 MPa to 0.60 MPa, however, the corner wear, the most predominant wear in all the cutting conditions in this study, increased. When the cutting speed was increased to 1.5 m/s, the tool life in MQL decreased drastically. These results suggested that when finishing Inconel 718, the special care must be taken for choosing the pressure of air supply and cutting speed. The obtained results provided a useful understanding of the complicated influence of MQL on the cutting performance of Inconel 718.