Mechanical Properties Analysis And Optimization Of Gantry Milling Machine Based On Finite Element Method

A milling machine is a machine tool that can perform a vast number of operations on solid materials, such as planning, slot and contouring, while keeping the balanced mechanical properties, the milling machine manufacturers ask for light weight and low cost of the product. With a gantry milling machine as its object of study, this paper applies Finite Element Method (FEM) software ANSYS to the mechanical analyses and design optimization.First, simplify the complex milling machine designs to be suitable for ANSYS modeling. Then create FEM model of the gantry milling machine with5different types of elements, i.e. structural solid element SOLID186, structural shell element SHELL281, structural mass element MASS21, beam element BEAM189and rigid beam element MPC184. Since a large model requires too many CPU hours, the author configured a distributed ANSYS system, enabling the computing to be done by two personal computers, thus improving working efficiency.Based on the above-mentioned model, static and dynamic mechanical analyses of the milling machine were carried out, after which the first principal stress contour diagram, three components of displacement and their vector sum contour diagrams were drawn. At this stage, the maximum stress point was found, making it clear that it is a linear elastic problem. Afterwards, first four modes and their corresponding frequency of the structure were obtained, providing a reference for subsequent design optimization. Topology optimizations of the gantry milling machine were performed in reference to the topology optimization principle. The influence of three features, i.e. girder with the upper right corner excised, column with the right part punched and column with the under part strengthened, were studied. Afterwards, six new design schemes were proposed, and the FEM results verified that excising the upper corner of the girder can reduce weight significantly but has little impact on structure stiffness, punching the right part of the column will cause massive negative effect on the structure and strengthening the under part of the column can raise the first mode frequency dramatically.At last, based on the best scheme of the gantry milling machine, parameter optimization was performed. Compared the new design with the original one, stiffness of the optimum design decreased by0.72%, volume reduced by36.54%, and the first mode frequency increased35.07%.