Dynamics of Prebending in Milling Stability Improvement for Thin-Walled Workpieces

Abstract Enhancing the stiffness of thin-walled workpieces is essential to suppress chatter during milling, and applying prebending to workpieces is an effective method to achieve this. A semianalytical dynamic model based on the variational method is developed to uncover how prebending curvature and direction modulate dynamic stiffness and milling stability. A fixture-based prebending technique is then applied to maintain the workpiece in its bent configuration during milling. Numerical analysis confirms the stiffness enhancement is generally applicable across various geometries, with the first natural frequency increased in all simulated cases and the increase exceeding 110% in high aspect ratio cases. Stability simulations indicate that prebending expands the stable spindle speed range, easing parameter selection under uncertainty. Experimental results show a transition from an unstable to a stable milling state at a spindle speed of 8000 rpm. The results validate the established dynamic model and demonstrate that applying prebending technique, with theoretically guided selection of curvature and direction, significantly improves milling stability.