Monitoring chip color change in ti6al4v alloy milling and investigating the effects of cooling/lubrication on chip morphology

Abstract

This study investigated how image processing technology and cooling/lubrication methods affect the change in chip color and chip shape when milling Ti6Al4V alloy. The focus was on solving the high temperature problem in the machining of titanium alloys, which are hard and have limited thermal conductivity. The experiment was carried out under the same standards as dry, coolant, MQL (minimum amount of lubrication), and cryogen. Experiment results showed that cooling and lubricating methods had an influence on chip morphology, with the chips morphing into tubular long spiral chips, conical short spirals, and short tubular chips. Dry machining produced distinctively adiabatic bands and saw-type chip formations. These structures were found to be at a lower level in the cryogenic cooling process than in other methods. Methods of cooling and lubrication were found to be effective on chip thickness, width, and radius. In addition, the color difference caused by burning in the chip depending on the machining temperature was investigated. The S (saturation ratio) of colors in the chip image processing rose in the order of cryogen, coolant, MQL, and dry machining (0.131623, 0.150836, 0.208414, 0.230374) technique. When the temperature change was evaluated according to the cooling and lubrication techniques, the lowest temperature was found in cryogenic processing; the temperature value rose by 25 % in fluid, 35 % in MQL, and 55 % in dry machining. As a result, the intention of this study is to improve machining performance by monitoring chip structures.