Quantitative Evaluation Method of Bending Stiffness Characteristics of Milling Chucks

Abstract

During milling process, the cutting force acts on tool end like cantilever bending, consequently, the deflection of cutting point cannot be avoided. In order to specify the deflection accurately, it is necessary to determine the bending stiffness characteristics of milling chucks. In this paper, the evaluation method of the bending stiffness characteristics is proposed concretely, and then, the characteristics of typical milling chucks are examined experimentally. The tool chucking region can be modeled mechanically as the equivalent spring distribution in the tool hole on milling chucks. Based on this model, the bending stiffness characteristics can be quantified with two parameters, such as the equivalent start depth l₀ of chucking force from the entrance of tool hole, and the equivalent spring coefficient k per chucking length. From the application results of the proposed evaluation method for typical chucks, the following are found out: the changes in these parameters depend upon the structure of tool chucking mechanism. Moreover, the bending stiffness of overall tooling including tool is influenced by not only chuck but also tool condition such as material property and chucking condition. Especially, the higher the tool stiffness is, the more remarkable the influence of the bending stiffness characteristics of chucks is.