Force-induced deformation prediction and flexible error compensation strategy in flank milling of thin-walled parts

摘要

Due to the weak rigidity of flexible thin-walled part and tool, deformation inevitably occurs under the action of a cutting force in the flank milling of thin-walled parts, resulting in reductions of the machining accuracy and efficiency. To solve the above problem, a force-induced deformation prediction model based on the static substructure method and a flexible error compensation strategy for the deformation of the thin-walled part and tool in flank milling are proposed. The tool is considered to be a cantilevered beam to calculate its deformation. The thin-walled part is divided into two substructures, namely, the substructure with the material to be cut (STBC) and the unmachined substructure, which remains unchanged. Deformation models of the two substructures are constructed based on the element stiffness matrix of the thin-walled part. The time-varying stiffness and the removed material from the thin-walled part are only updated in the deformation model of the STBC. The deformation model of the entire thin-walled part is constructed by coupling the deformation models of the two substructures. In this way, the degrees of freedom of the deformation model of the entire thin-walled part are significantly reduced. To reduce the deformation error, a flexible error compensation strategy is proposed. The tool location at the initial feed position is directly compensated by the mirror principle. For the other tool locations, the tool location at the next feed position is adjusted with the compensated tool location at the previous feed position as the initial iteration value. This flexible error compensation strategy is based on the continuity of the compensated toolpath, which is close to the actual cutting process and adjusts the tool locations with high convergence. Finally, the proposed methods are proven via flank milling experiments. The deformation prediction results agree with the experimental results, and the deformation errors are reduced greatly after error compensation by using the proposed strategy.