An experimental investigation on contact length during minimum quantity lubrication (MQL) machining

This paper describes experimental investigations on influence of different media such as minimum quantity lubrication (MQL), compressed air and emulsion on tool–chip contact length. The results are compared with dry cutting in terms of tool–chip contact and chip morphology. The tool–chip contact area was examined with scanning electron microscopy (SEM), optical microscopy and white light interferometer. The orthogonal turning test series were planned in such a way that the engagement time was altered from long to very short (intermittent turning). The results showed that MQL and compressed air lowers the contact length compared to dry cutting at short and longer engagement times. The contact length is almost the same for MQL and compressed air assisted cutting, but the difference is in sliding region with the shorter engagement times. Emulsion assisted cutting gave the shortest contact length. The chips were also examined with optical and scanning electron microscopy. Wider chips were observed with dry cutting which is a result of side flow. Different oil amount was also investigated with TiN coated inserts. The effect of oil and air component of MQL on the contact length is understood that helps to clarify their role in the whole process. It is concluded that MQL is a very suitable method for short engagement time machining.