Design and evaluation of an embedded double jet nozzle for MQL delivery intending machinability improvement in turning operation

Minimum quantity lubrication (MQL) is a promising solution as an alternative to conventional flood cooling and dry machining. It is a bridging technology between the dry and conventional flood cooling. In this work, an embedded double jet nozzle has been designed and developed for enhancing the effectiveness of MQL. Grey based Taguchi multi-response optimization was applied to find out the MQL parameters (i.e. nozzle size, nozzle angle, air pressure and oil flow rate) for reducing cutting temperature, surface roughness, chip reduction coefficient and main cutting force. Consequently, the MQL and nozzle parameters were ranked. In this regard, Taguchi's orthogonal array (L18) was used for experimental design. GRA (Grey relational analysis) was employed to convert the multiple objectives (responses) into a single objective and finally, Taguchi's S/N ratios were used for optimization. The analysis results demonstrated that the most influential factor for an optimum response was nozzle diameter followed by air pressure, secondary nozzle angle, oil flow rate and primary nozzle angle and their optimum values are 1 mm, 19 bar, 15 degrees, 80 ml/h and 20 degrees respectively. A confirmation test was conducted to verify the feasibility of using a grey-based Taguchi optimization method. In the final part of this work, the performance of double jet MQL micro nozzle was compared against dry machining and single jet MQL machining and found most effective among three machining condition regarding cutting temperature, surface roughness, chip reduction coefficient, main cutting force and tool wears in turning medium carbon steel by coated carbide insert. A supplementary benefit of this simple embedded double jet nozzle is set up time minimization and consistent cooling without extra supervision.