Improved spindle dynamics identification technique for receptance coupling substructure analysis.

摘要

Knowledge of the tool point dynamic response is required if milling process models are to be used to select parameters that avoid chatter, improve surface finish, and increase part accuracy. The dynamics of the tool-holder-spindle-machine (THSM) can be obtained by modal testing, but, for the large number of tool-holder combinations in a production facility, the measurements are time consuming and, at times, inconvenient (e.g., micro-scale tools).;The Receptance Coupling Substructure Analysis (RCSA) approach may be applied as an alternative to modal testing. In this approach, the THSM assembly is considered as three separate components: the tool, holder, and spindle-machine. The modeled tool and holder receptances (or frequency response functions) are analytically coupled to an archived measurement of the spindle-machine receptance.;In this research, a novel approach to determine the spindle dynamics, referred to as the Euler-Bernoulli (E-B) method, is proposed. The spindle dynamics obtained by the new method are compared to two existing methods (referred to here as the synthesis and finite difference approaches) using a new comparison metric (CM). The subsequent THSM receptance prediction accuracy for all three spindle dynamics identification methods is evaluated using the CM. It is shown that the E-B method is the best alternative.;Using the E-B method to identify the spindle dynamics, a flexible (rather than rigid) connection is introduced between the holder and the tool to further improve the prediction accuracy. Measurements of various tool blank (i.e., a rod with no cutting flutes), holder, and spindle combinations are performed. A least squares non-linear error minimization technique is used to determine the stiffness values that represent the flexible tool-holder connection. The approach is validated using several endmill-holder-spindle assemblies.