Milling is one of the most common manufacturing processes in industry. Despite recent advances in machining technology, productivity in milling is usually reduced due to the process limitations such as high cutting forces and stability. If milling conditions are not selected properly, the process may result in violations of machine limitations and part quality, or reduced productivity. The usual practice in machining operations is to use experience-based selection of cutting parameters which may not yield optimum conditions. In this two-part paper, milling force, part and tool deflection, form error and stability models are presented. These methods can be used to check the process constraints as well as optimal selection of the cutting conditions for high performance milling. The use of the models in optimizing the process variables such as feed, depth of cut and spindle speed are demonstrated by simulations and experiments.

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Analytical models for high performance milling. Part I: Cutting forces, structural deformations and tolerance integrity

Peripheral milling of very flexible, cantilevered plates with slender end mills is modeled. The plate has varying structural properties in the axial and feed directions due to metal removal. The cutter is modeled as a cantilevered continuous elastic beam with flexible clamping in the collet. The plate structural properties are updated using the finite element technique as the cutter and plate interact at changing contact zones along the feed direction. The analytical cutting force and surface generation model considers partial separation of tool and plate structures due to static displacements. The experimentally verified model predicts the cutting forces and dimensional surface error on the plate. The model identifies the required feed variation along the plate in order to keep the static form errors within the specified tolerance of the part. The model is developed to improve dimensional accuracy in peripheral milling of very flexible aerospace components.

Modeling and avoidance of static form errors in peripheral milling of plates

Identification of chatter free cutting conditions, the chatter stability lobes, requires a measurement of the frequency response function (FRF) of each tool mounted on the spindle. This paper presents a method of assembling known dynamics of the spindle–tool holder with an analytically modeled end mill using the receptance coupling technique. The classical receptance technique is enhanced by proposing a method of identifying the end mill–spindle/tool holder joint dynamics, which include both translational and rotational degrees of freedom. The method requires measurement of FRFs with impact tests applied on the spindle–tool holder assembly and blank calibration cylinders attached to the spindle. The spindle and tool holder characteristics are completely identified from the two experiments, and used for the mathematical prediction of FRF for end mills with arbitrary dimensions. The proposed method is experimentally proven and verified in cutting tests.

D.T. Vo

Papers

Determination of the Equivalent Diameter of an End Mill Based on its Compliance