Improving Surface Quality in CNC Turning of Aluminum Alloy with Hybrid Nanofluid: A DMAIC and Response Surface Methodology Approach

The machining of aluminum alloys and stainless steel is critical in industries that fabricate complex components. Recent advancements in nano-fluid-assisted lubrication techniques have significantly improved machining performance and supported sustainability and environmentally friendly practices for manufacturers. In manufacturing, particularly in turning processes, the surface finish of the final product is a critical determinant of overall quality. This paper presents a hybrid approach to optimizing the application of nano-cutting fluid during aluminum alloy (AL-6061) machining to enhance surface roughness. The proposed methodology demonstrates a nanofluid application strategy under the Six Sigma DMAIC framework integrated with Design of Experiments (DOE) to meet stringent aerospace industry quality standards. The experimental data were analyzed using the response surface methodology (RSM) to optimize the machining parameters. The results demonstrated a substantial reduction in surface roughness when employing a 1.5% volume concentration of SiO₂ nano-cutting fluid with MQL. In addition to the primary factors, significant two-factor interactions were observed, contributing to the effectiveness of the process. The optimized combination of hybrid nanofluid, cutting speed, and feed rate achieved a desirable surface roughness (Ra) of 0.92908 μm, with a 95% confidence interval of 0.7771 to 1.0826, making it ideal for AL-alloy machining. Applying high-concentration nano-cutting fluid improves surface quality for materials like aluminum alloys and provides an improved quality management strategy for small and medium enterprises (SMEs) through enhanced machinability and process efficiency.