Parametric finite element modeling and pose-dependent natural characteristics of a five-axis machine tool

Abstract

Five-axis machine tools exhibit pose-dependent structural dynamics, but repeated full finite element reconstruction across the workspace is computationally inefficient. We developed a parametric finite element workflow in ANSYS APDL for a five-axis machine-tool analog specimen. The structure was divided into six modules; regular regions were sweep-meshed and irregular regions were represented with quadratic SOLID186 elements using nominal element sizes of 20, 10, and 5 mm. Bearing, ball screw-nut, and linear guideway-slider joints were represented by equivalent springs. Twelve screw-nut and guideway-slider stiffness parameters were calibrated with a genetic algorithm against the first six natural frequencies measured at one reference pose. Movable joint locations were updated from the X-, Y-, Z-, A-, and C-axis pose variables while the identified joint stiffness values were held constant. At the reference pose, the mean and maximum frequency discrepancies between the calibrated model and experiment were 3.29% and 8.78%, respectively. Workspace calculations predicted that the first natural frequency decreased as the beam center of gravity rose, whereas spindle-dominated local modes showed similar trends among working planes. Because calibration and model checking used the same reference-pose data and no multi-pose modal measurements were available, the reported workspace trends should be interpreted as model-based predictions rather than independently validated responses.