Investigation of machining parameters and cooling strategies on the burr geometry in micro-milling of titanium alloy (Ti–6Al–4V)

Titanium-based alloys are indispensable in aerospace, biomedical, automotive, and marine applications due to their exceptional strength-to-weight ratio, high-temperature capability, biocompatibility, and corrosion resistance. However, micro-milling of Ti–6Al–4V is prone to burr formation, which necessitates post-processing that can damage delicate micro-features and compromise dimensional fidelity. This study systematically compares burr formation across conventional, transition, and high-speed cutting ranges under different cooling strategies and statistically quantifies how feed per tooth, cutting speed, depth of cut, and cooling govern burr width and height on the up and down-milling sides. Micro-milling experiments varied these factors; burr metrics were measured and analyzed using a variance-based contribution approach. Results show that across the three speed ranges, the transition-speed window yielded the most favorable outcomes, with minimum burr at Vc ≈ 75 m/min. Burr width was governed mainly by feed per tooth and cutting speed, both inversely related to width; their combined contribution ranged from 82 to 89 % (up-milling) and 69–92 % (down-milling). Burr height was dominated by depth of cut and feed per tooth; each directly related to height; their combined contribution ranged from 77 to 90 % (up-milling) and 74–85 % (down-milling). Under the optimized parameters, burr width decreased by 19 % (up-milling) and 9 % (down-milling), and burr height decreased by 25 % in both milling directions.