Influence of Cutting Wedge Geometry Design on Cutting Forces, Chip Formation and Surface Roughness During Free Machining of Aluminum Alloy

This study investigates the effects of the rake angle and clearance angle of custom-manufactured HSS-E Co5 high-speed steel cutting tools on the Fc main cutting force, the Fp passive force component, the Ra and Rz surface roughness parameters, and chip morphology during orthogonal free cutting of EN AW-7075-T6 aluminum alloy. A dedicated experimental fixture was designed and manufactured for the measurements, providing highly accurate depth-of-cut adjustment and ensuring excellent repeatability of the experiments. A full-factorial experimental design was employed, in which the rake angle varied between 0° and 30°, while the clearance angle ranged from 5° to 15°. Three independent cutting trials were performed for each tool geometry. The results showed that increasing the rake angle significantly reduced both the main cutting force (Fc) and the passive force (Fp), whereas increasing the clearance angle resulted in higher force values. Surface roughness analysis revealed that the clearance angle was the dominant factor affecting surface quality. The highest Ra and Rz values were measured at a clearance angle of 15°. Two-way analysis of variance confirmed that the rake angle, the clearance angle, and their interaction had statistically significant effects on the Fc, Fp, Ra, and Rz results. The clearance angle exhibited the strongest effect on Fc, Ra, and Rz, whereas the rake angle had the strongest influence on Fp. Chip morphology observations demonstrated that larger rake angles promoted smoother chip flow and reduced chip compression, while smaller rake angles resulted in thicker and more tightly curled chips. Overall, the combination of larger rake angles and smaller clearance angles provided the most favorable machining conditions, resulting in lower cutting forces, improved chip formation, and enhanced surface quality.