| Summary: | 碩士 === 國立虎尾科技大學 === 機械與機電工程研究所 === 97 === A numerical model and frequency response measurement of the machine tool spindles and grinding machine tool structures commonly utilized in industry are analyzed in this study. The performance of the spindle directly affect the machining productivity and finish quality of the workpieces, plays a significant role of the machine tools. Grinding have been widely used in precision processing industry. The manufacture of each machine or electronical components all toward precision development trend. Therefore, the rotary table surface grinding machine structure and machine tool spindles are selected as the objects for the numerical simulation, frequency response measurement, analysis, diagnosis and assessment in this study.
The static stiffness and vibration mode shapes of the machine tool spindles and grinding machine were analyzed by using a commercial finite element analysis software in order to determine the natural frequency and vibration modes. Moreover, the finite element model for spindle-bearing system is established enabling the variation of spindle stiffness calculations under different bearing preloads. On the other hand, the spindle stiffness may also be obtained from the experiment and its result may be utilized to validate the theoretical calculations. The load is acted by weights at different directions and orientations, and their corresponding deformations are measured through dial indicator. Three bearing preload conditions, i.e. light, medium and heavy preloads are selected, which are imposed on the bearing to investigate the spindle stiffness variation, respectively. In addition, the effects of the geometrical parallelism error at the end surfaces of spacer due to the manufacturing tolerance or some imperfection on the spindle rotational stiffness are studied. The impact test on the machine tool spindle, grinding machine tool structures , grinding machine tool components such as the bed, saddle, ribbed column, rotary table and headstock is performed by hammer and the corresponding vibration signal on the surfaces is acquired by accelerometer, the natural frequency of the machine tool spindle and grinding machine structures were measured experimentally, the spindle stiffness may be reflected in the other manner through the signals processing by spectrum analysis. The relationship between spindle stiffness and frequency response may be obtained consequently. The dynamic behaviors of grinding machine’s spindle and rotary table were examined. From comparison of the numerical simulation calculated results with experimental results, it can avoid the resonance vibration when the machine operate, enhance reliability of machining process. A build up response measurement, analysis, diagnosis and assessment is benefit for design new structures of machine tool in the future.
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