Dynamic Analysis of the Finite Element Model of the Prototype Whole Machine of the Gantry Machining Center

Dynamic Analysis of the Finite Element Model of the Prototype Gantry Machining Center (1) Modal Analysis. The designed high working speed of the prototype 5-axis gantry machining center is 10,000 r/min. Since the excitation frequency acting on the machine tool is generally low, only the low-order modal natural frequencies are likely to coincide or be close to the excitation frequencies. The natural frequencies of the high-order modes are far higher than the possible excitation force frequencies, and resonance is generally not expected to occur, which has little impact on machining quality. Therefore, only the low-order modes of the machine tool need to be studied. Conducting modal analysis on the finite element model of the prototype machine can clearly show the dynamic characteristics of the machine tool, with the 1st, 3rd, and 5th order vibration modes being particularly significant. The natural frequencies and vibration modes of these three orders are shown in Figure 3. Modal analysis results. (2) Harmonic Response Analysis. Modal analysis can provide the vibration modes and natural frequencies of the entire machine, but this only indicates the relative vibration conditions of various parts of the machine tool. The effects of external force excitation on the vibration response of different modes are not the same, so conducting harmonic response analysis on the entire machine can better illustrate the vibration resistance performance of the machine structure under dynamic interference excitation. A simple harmonic force with amplitude of 1000 N in the X, Y, and Z directions was applied at the tool installation position of the original machine's finite element model. Based on the dynamic characteristics obtained from modal analysis and the excitation force frequency under actual working conditions, the frequency of the simple harmonic force was set in the range of 40 to 140 Hz, using this simple harmonic force to excite the entire machine. Figure 4 shows the vibration response of the machine tool under the excitation of simple harmonic force in this frequency range. From the results of the harmonic response analysis of the prototype machine, it can be seen that under dynamic cutting force excitation, the 1st, 3rd, and 5th order modes are easily excited. Combining with modal analysis, it can be inferred that the 1st order vibration mode is mainly due to the relatively weak Y-direction stiffness of the sliding seat and the column; the 3rd order vibration mode is mainly due to the twisting deformation of the crossbeam; and the 5th order vibration mode is primarily caused by the twisting deformation of the crossbeam and the bending deformation of the box structure. Therefore, the crossbeam structure is a weak point in the structural design of the gantry machining center. Improving the structure of the crossbeam and appropriately increasing its torsional stiffness while reducing the deformation of the machine tool under dynamic cutting forces is key to further enhancing the dynamic and static performance of the entire machine. For more information about gantry machining centers, please visit: http://www.yxskkj.com.cn