Phenomenological insights into surface generation and tool dynamics during tangential milling of Ti-6Al-4V alloy

• Barrel end mill kinematics governs surface generation on Ti-6Al-4 V. • Climb milling inherently ensures superior surface quality over conventional milling • Non-linear tool bending dynamics indicate critical process stability transitions at ae = 1.5 mm. • Engaging with larger tool diameter reduces deformation, enhancing precision. Efficient and precise machining of challenging materials like Ti-6Al-4 V alloy necessitates a profound understanding of the fundamental phenomena governing tool-workpiece interaction. This study addresses a critical gap in comprehending how varying radial engagement (ae) and distinct material engagement strategies with tangential milling cutters (barrel end-mill) mechanistically influence surface generation and tool dynamics under Minimum Quantity Lubrication (MQL) conditions. The research investigates the impact of ae values and initial contact point (small vs. large cutter diameter) on surface roughness (Ra, Rz) and recorded tool forces (Mmax, Tmax). A central objective is to elucidate the generic principles guiding surface formation and tool loading, moving beyond mere parameter optimization for a specific application. The methodology involved experimental milling on Ti-6Al-4 V blocks, utilizing a ϕ12 mm barrel-shaped cutter across ae values of 0.5 mm, 1.5 mm, and 3 mm, while maintaining a cutting speed of 60 m/min, a feed per tooth of 0.048 mm/tooth, and an axial depth of cut of 0.20 mm. Results reveal that engaging the workpiece with the larger cutter diameter generally leads to superior surface quality for ae > 0.5 mm, attributable to altered kinematic conditions promoting smoother material flow. Furthermore, a non-linear increase in Mmax at ae = 1.5 mm suggests a crucial transition in cutting stability. This investigation provides generic phenomenological insights into the intricate interplay between tool geometry, engagement kinematics, and material response, offering foundational knowledge for advanced process design in machining difficult-to-cut alloys.