Optimization of milling parameters of 1018 steel and nanoparticle additive concentration in cutting fluids for enhancing multi-response characteristics

In this study, the optimization of the processing parameters and nanoparticle additive concentration in the cutting fluid for a milling process carried by Computer Numerical Control (CNC) was performed. Machining operations commonly present high wear on the cutting inserts. This translates into a limited tool lifespan, poor surface finish of the workpiece, and high energy consumption by the process, as well as high manufacturing costs. The nanoparticle (NP) selected for this study was a montmorillonite clay (MMT) due to being naturally occurring, inexpensive, and environmentally friendly. Nanolubricants were prepared with a MMT clay concentration of 0.2 and 0.3 wt%. A three level Box Behnken experimental design was performed in order to optimize the input parameters for milling of an AISI 1018 steel, such as: cutting speed, feed rate, depth of cut, and nanoparticle concentration in the cutting fluid. A total of 27 different combinations of these parameters were done by this method. Response characteristics investigated were: spindle load (related to power consumption), cutting insert radius (wear), and surface roughness (quality of the AISI 1018 steel work-piece). For the spindle load, it was found that NP addition had a significant effect. The results of the model for this response parameter indicate that the determination coefficient (R²) was 99%. The R² of the model for the cutting insert radius was 93% and the results of the analysis of variance (ANOVA) showed that NPs had a significant effect when combined with the parameters of cutting speed and feed rate. The optimal range of values for the four input parameters that enhanced all three response characteristics were: a cutting speed of 1145–1182 rpm, depth of cut of 0.02–0.03 in, feed rate of 7–8 in/min, and MMT clay NP concentration of 0.13–0.15 wt%. The results obtained in this study demonstrate the benefit of green nanoadditives in cutting fluids and optimization of processing parameters for enhancing the efficiency of milling processes.