工具機主軸對流係數和熱產生

Convection Coefficient and Heat Generation of Spindle in Machine Tools

本研究目的為評估主軸運轉在施加負載下所產生的熱功率，以便預估工具機操作時之熱變形。首先分別在絕熱、自然對流和強制對流情況下，以實驗量測主軸在不同負載和轉速下運轉的溫升。絕熱過程是以隔熱材料包覆主軸，使主軸表面保持最低的平均對流係數。接著以CAE 執行暫態熱傳導分析。比較實驗與分析數據，求出主軸之熱功率與對流係數，再以曲線擬合計算其誤差，並且進行溫度誤差值範圍之模擬。結果顯示，主軸發熱量會隨負載或轉速的增加而上升，且轉速對主軸發熱量影響較大，因此轉速的增加，提升了主軸表面的對流係數，從而降低因熱功率增加造成的溫升效果。

This study was aimed at evaluating the heat generation of a spindle topredict thermal deformation of machine tools during operation. Firstly,empirical measurements were performed to determine temperature rises ofa spindle under different loadings levels and rotating speeds, for insulated,natural convection, and forced convection conditions. For the insulatedcondition the spindle was wrapped in a thermal insulating material toensure a lowest average convection coefficient attainable. Transientthermal CAE analyses were then implemented to simulate the experimentalconditions. The experimental values were compared with the simulationdata to identify the heat generation rate and the convection coefficient forthe spindle. The errors were determined by using curve fitting. Theerror range of temperature prediction was identified using computersimulation. The result indicated that heat generation increases with increasing loadings or rotating speeds, and the rotating speed has a moresignificant effect on heat generation of the spindle. Hence, an increase inrotating speed enhances convection on surfaces of the spindle, which inturn lowers the temperature rise as a result of heat generation.