Design and development of pulse jet minimum quantity lubricant (MQL) applicator and its effect on surface milling of hardened AISI 4140 steel

Abstract

Modern manufacturing industries are seeking different alternatives to attain the need of higher machining speeds, lower wastage and a better product quality as well as reducing the cost of the manufacturing process.An approach to this problem is considering high speed machining but high speed machining at high speeds and feeds generates large heat and high cutting temperature, which shortens the tool life and deteriorates the job quality. To reduce this high temperature machining of hardened medium carbon steelneeds large quantities of cutting fluid to be applied which not only incur expenses but also can cause grave environmental and health hazards. Dry machining might be an alternative in this context and is totally free from the problems associated with cutting fluid but is difficult to implement on the existing shop floor as it needs ultra-hard cutting tools and extremely rigid machine tools. The manufacturing industries hence are looking to mitigate these problems by experimental investigations and by adoption of advanced techniques such as cryogenic cooling, high-pressure coolant, and minimum quantity lubricant (MQL) application. Among these, Minimal Quantity Lubrication machining is found to be quite effective in improving tool life and surface finish. In this research work surface milling of AISI 4140 steel (40 HRC)was investigated with pulsed jet Minimum Quantity Lubricant (MQL) applicator using straight oil as the cutting fluid. The investigation was carried upon comparing the performance of MQL applicator on the basis of tool wear, cutting force, and surface finish. The effects of different cutting parameters were compared at different combinations of feed, depth of cut and cutting conditions. A pulsed jet MQL applicator was designed and developed with the help of full factorial analysis (Design of Experiment) and it was ensured that the cutting fluid can be applied in different timed pulses and quantities at critical zones during surface milling.An investigative comparison with dry milling under same conditions has been done to evaluate the relative performance of hard milling with MQL applicator. It was observed that the MQL applicator system for surface milling on hardened steel can bring forth better performance when compared to dry milling.