主軸為工具機上,帶動刀具或工件旋轉進行加工程序的旋轉軸。 其性能表現取決於剛性、迴轉精度、實用轉速。目前國內工具機所採 用的主軸大多搭配接觸式滾動軸承,滾子與內、外環相互碰撞摩擦, 有其壽命限制。進行加工的過程中較易產生振動,影響表面粗糙度。 主軸驅動部分,分為皮帶式、齒輪式、直結式和內藏式,其中內藏式 主軸即是將主軸之動力來源—馬達,整合至主軸內部,除了節省外部 動力來源的空間外,還有迴轉精度佳、較低功耗等優點。使用液靜壓 內藏式主軸預期將能夠有效提升工件表面品質並延長主軸壽命。但由 於液靜壓內藏式主軸將馬達與液靜壓軸承同置於主軸殼體內部,因此 在設計以及零件選用上均較其他形式的主軸更為複雜。
本研究針對現有液靜壓內藏式主軸進行測試,紀錄實驗結果與實 驗中所觀察到的問題,並且了解問題發生的原因。之後進行主軸的設 計改進、製作與組裝,最後重新架設實驗平台進行實際測試,記錄數 據與觀察實驗中的現象,評估改進後主軸之性能表現。

In order to achieve very fine surface roughness, hydrostatic bearings are extensively used in optical mold machining and the precision grinding machining. Hydrostatic bearings have the advantages of low friction, high rotary precision, good damping characteristic and long operating life.

In this study, the simulation of orifice-compensated bearing lubricant was introduced by solving Reynolds equation with finite difference method to evaluate the recess pressure, load capacity, and the flow rate. By the results of the simulation, we designed a built-in grinding spindle, containing two hydrostatic thrust bearings and two hydrostatic journal bearings. Concerning the compact characteristic of orifice restrictor , it is suitable for a built-in spindle. Bearings used in a built-in grinding spindle were all orifice-compensated.

In this study, we measured the change in recess pressure by changing the supply pressure. Furthermore, we applied radial load on shaft and measured displacement to evaluate load capacity and radial stiffness of hydrostatic bearings in a built-in grinding spindle . Finally, a conclusion was drawn based on comparisons of the experimental results and simulation results.

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