Machinability and tribological analysis of used cooking oil for MQL applications in drilling AISI 304 using a low-cost pneumatic operated MQL system

Developing low-cost MQL systems and application of used/waste cooking oil (generated in restaurants/homes), which poses a health risk if it enters the food chain again, as feedstock for MQL applications can increase the adoption of MQL by smaller manufacturing industries. A low-cost pneumatic-based MQL system that works only on compressed air is developed and tested. The droplet size and velocity of the MQL aerosol are analysed using CFD to arrive at an optimum nozzle design and the nozzle spray characteristics are studied using a Phase Doppler Particle Analyzer. Drilling of AISI 304 using the MQL system with commercial MQL oil and used cooking oil is carried out and the results are compared with flood cooling. The thrust and radial forces are comprehensively analysed and related to the tool wear, built-up edge (BUE) formation along the drill cutting edges, and chip morphology. It is found that a steady drilling process is obtained with used cooking oil because of its superior viscosity (resulting in lower friction) and lower surface tension (leading to smaller droplet size and better wettability).