Response Modeling and Optimization of Process Parameters in Turning Medium Carbon Steel Under Minimum Quantity Lubrication (MQL) with Vegetable Oil and Oil Blends

Machining is an important aspect of manufacturing. The application of cutting fluid in the field of engineering manufacturing has a history of hundreds of years, and it plays a vital role in the processing efficiency and surface quality of parts. The use of vegetable oil in machining operations is receiving attention currently for sustainable alternatives to mineral-based cutting oil. If the vegetable oil is applied through the minimum quantity lubrication (MQL) technique, it becomes more cost effective, eco-friendly, and sustainable. This study aims to investigate the effects (cutting force and temperature) of coconut oil, a coconut–rice bran oil blend, and a coconut–olive oil blend, and compare them with VG 68 oil using MQL. A magnetic stirrer was employed for mixing oils (coconut–rice bran oil and coconut–olive oil), performed at 40 °C and 250 rpm. The response parameter values were evaluated at different combinations of speed (78, 113.5, and 149 mm/min), feed (0.1, 0.13, and 0.16 mm/rev), and depth of cut (0.5, 0.75, and 0.1 mm). The design of the experiment (DOE) was created using the value of input parameters using response surface methodology (RSM). Percentage (%) reduction was calculated to compare the reduction in cutting force and temperature by using coconut oil, a coconut–rice bran oil blend, and a coconut–olive oil blend concerning mineral oil. Empirical models were developed for cutting force and temperature by RSM for the four cutting environments. The ANOVA result shows that the model performed satisfactorily for both temperature and force analysis. RSM-based optimization was carried out and the optimal solution was found at the cutting speed of 80.15 m/min, feed rate of 0.10 mm/min, and 0.5 mm depth of cut for the coconut–olive oil blend. Also, the model performed better in the reduction in force than temperature.