| Summary: | 碩士 === 國立勤益科技大學 === 機械工程系 === 106 === Spindle is the core component of machine tools processing, and machining performance depends on the advantage and disadvantage of the spindle. Temperature rise resulted from bearing and drive motor causes structural components of spindle to have thermal deformation, which results in spindle deviation of axial and radical direction, especially on the condition of high-speed and high-precision operation. What’s more, temperature rise leads bearing to deviate from its initial defaults for pressure and change tool system dynamic response characteristics, which affects the range of cutting stability as well as the quality and performance of cutting processing. Thus, the study on the influence of spindle temperature rise is the chief basis for later development of accuracy compensation technology and design of spindle system. Axial thermal error prediction model and machine stability variation prediction are the most important premises.
The purpose of this study is to establish correlation between dynamic temperature field and thermal deformation of high-speed main spindle of machine tools, develop a
mathematical model, and evaluate the influence of temperature rise on spindle tool cutting stability. The result can be used as a basis for post-stage thermal deformation suppression or compensation and the adjustment on tool cutting parameter during machining operation, which enhances spindle performance and processing efficiency.
According to the whole machine thermal temperature rise and elongation test results, there is a positive correlation between the level of temperature rise of main spindle in bearing or motor and the axial extension of main spindle shaft. Multivariate regression analysis is used in this study to establish an axial thermal elongation prediction model. Relative error between thermal elongation and measured value, predicted by a mathematical model developed from four-point temperature variable, is less than 4.0um (8%). On the other hand, thermal steady state prediction error, predicted by a mathematical model developed from a single point motor temperature variable, is less than 2.5 um (6%). It shows that using motor temperature as the input variable can precisely predict thermal elongation caused by spindle at different speed. In addition, there is a consistency in the experiment result and the study using finite elements to analyze and predict temperature rise of bearing and motor. This model can be used to predict and analyze post thermal deformation and dynamic response. Spindle vibration experiment results show that spindle temperature rise affects the end of hilt dynamic rigidity and that temperature rise of bearing changes preloading rigidity and damping. According to analysis of cutting stability, there is a distinct difference of main spindle tools between cold and heat conditions. Such difference shows that proper alternation of tool cutting parameter during cutting processing helps enhance spindle performance and processing efficiency.
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