High-speed machining of aluminium alloy using vegetable oil based small quantity lubrication

Abstract

In an attempt to investigate the effectiveness of vegetable oil based small quantity lubrication in high-speed machining of aluminium, this study finds that its usefulness is more significant in an intermittent cutting process like end milling than in turning, where continuous cutting happens. The investigation was carried out using small quantity lubrication aerosol, produced by air atomization of sunflower oil at the rate of 100 ml/h for each cutting zone. In the high-speed turning operations, uncoated and polycrystalline diamond–tipped WC inserts were used. 5%–20% reduction of cutting force could be realized by small quantity lubrication application, compared to dry environment. The highest order of reduction was observed when the cutting velocity was increased from 700 to 1000 m/min. At lower velocities, small quantity lubrication effect was almost insignificant. However, high-speed end milling operations received substantially superior benefit by small quantity lubrication application. The reduction of feed force was 30% or more among different cutting speeds. The beneficial effect of small quantity lubrication application was significantly more in machining commercially pure 1050 grade of aluminium than 7075 alloy. The required prevalence of the thick-film lubrication at the interface of chip and tool rake for arresting any possible diffusion of aluminium to tool material was significant in the intermittent cutting since every cutting edge drew in fresh micro-droplets of lubricant before resuming cutting in its next cycle of engagement with workpiece. Interestingly, the end milling performance of small quantity lubrication–assisted uncoated carbide was so good that diamond-coated tools were not necessary. Surface roughness profiles, chip morphology and traces of built up edge formation were critically investigated and the results clearly indicated the predominantly more favourable outcome of small quantity lubrication application in end milling, compared to turning.