Study of comparing cutting force signal features for dry, air cooling and minimum quantity lubrication (MQL) drilling

Abstract

Applying Minimum Quantity Lubrication (MQL) for machining processes such as drilling can obtain process performance improvement comparing with completely dry situations, and reduce the use of machining fluids considerably comparing with flood cooling. Although many researches have been reported on the comparison of temperature, tool wear, surface roughness and chip patterns between dry and MQL cutting, relatively fewer literatures about the cutting forces and their features can be found. In this paper, first dry and MQL drilling of cast iron, S45C, SUS304 and Ti alloy were conducted, and then life term of dry, air cooling and MQL drilling of SUS304 were carried out. TiCN coated HSS drill bits with double inner coolant holes were applied to produce air cooling and MQL internally. The thrust force and torque were monitored by a dynamometer and, time, frequency, and time-frequency domain features of them are extracted and compared. Especially there are some newly generated features derived from transforming the thrust force and torque to two orthogonal forces and further being analyzed in a rectangular coordinate. Experiment results show that, for different workpiece materials MQL affects different force features in different ways and for SUS304 tool life is greatly lengthened, friction is suppressed, chip jamming is alleviated and both the static and dynamic components of cutting forces reduce when air cooling and MQL are applied. Moreover, it is revealed that the differences of features between dry and other two conditions are quite obvious but those between air cooling and MQL are inconspicuous.