Improving the stiffness of the milling machine by optimizing the arrangement of internal rib stiffeners and distributing the wall thickness of the column

The static deflection of the machine tool and thus the displacement of the tool due to the high machining forces is the most important factor in reducing the dimensional accuracy of the workpiece. Also, the overlap of the frequency range of operation with the machine natural frequencies causes an undesirable resonance phenomenon. Reducing the strain energy of the column and thus reducing the displacement of the tooltip, and increasing the first natural frequency of the milling machine, given that the frequency range of operating is below the first natural frequency, is a desirable change that can be achieved by optimizing the distribution of the wall thickness of the column and the arrangement of the internal rib stiffeners. In this paper, a method based on sensitivity analysis was presented to optimize the arrangement of rib stiffeners connected to plate and shell structures. In each step of optimization, by establishing a loop of relationship between MATLAB and ABAQUS software and based on the sensitivity analysis performed by the finite element solver, the stiffeners that have the greatest impact in optimizing the objective function are added to the design space. After optimizing the distribution of the wall thickness of the column using the ABAQUS software size optimization module, the method presented in this paper was used to optimize the arrangement of internal rib stiffeners. Ultimately, despite a 0.5% reduction in the weight of the column, the maximum displacement of the machine tool decreased by 6.9% and the first natural frequency increased by 16.5%.