Layout evaluation at earlier stages of machine tool design:form-shaping function-based approach

Some important parameters of the machine tool layout have to be selected in the early stages of design when a shortage of information makes application of the finite element method impractical. As a computer-aided tool in these stages, the form-shaping function (FSF)-based approach can be used. It allows evaluation of the kinematic and geometric errors and compliance issue static deformations, which contribute significantly to the total machining error as applied to precision machine tools. The FSF-based methodology gives important information allowing layouts' comparison and structure optimization under uncertainty in requirements and limitations relating to the designed machine under strong time constraints. Six different layouts of a turning center are investigated to compare the effect of geometrical errors and compliance of machine structure on part accuracy in the range of less than five microns. Motion errors of machine tool components were measured by laser equipment during machine tool assembly and inspection. Compliance-induced errors are included in the evaluation to take into consideration cutting forces. Obtained data were used as the input for simulation of machining a sample workpiece-a sphere whose size, position, and form errors are used as criteria for layout comparison. Since the FSF-based results correlate well with the experimental data, the developed approach can be considered as an effective tool for application in the early stages of machine design.