Optimization and improvement of stable processing condition by attaching additional masses for milling of thin-walled workpiece

Light weight is the main design requirement for minimizing costs or fuel consumption in mechanical equipments, and it, together with the material removal rate (MRR) requirement, also brings an important source of chatter, which still remains as an essential phenomenon to be suppressed in the future. This paper investigates the stable cutting region optimization problems in milling of structures with low rigidity. An effective method is proposed to improve the chatter stability by attaching appropriate additional masses to the workpiece, and thorough studies are also carried out to reveal the effect of additional masses on chatter stability. An efficient method based on structural dynamic modification scheme is developed to calculate the varying dynamics of the in-process workpiece under the combined effect of additional masses and material removal during milling process. Typical characteristic of this method lies in that only one modal analysis is needed to be performed on the finite element (FE) model of the initial workpiece, and the mode shape and natural frequency of the workpiece after attaching additional masses and removing material at each tool position can be calculated without the requirement to rebuild the FE model of the in-process workpiece. Based on the proposed dynamic modification scheme, an optimization algorithm is established to obtain the optimized combination of additional masses and the suitable stable cutting region for the achievement of maximum MRR. The proposed method is verified by milling process of a set of thin-walled workpieces, and comparisons of predictions and measurements show the validity and reliability.