Tolerance Design of a Close-Type Hydrostatic Slideway

液靜壓滑軌具有高剛性、低摩擦並同時擁有阻尼特性之優點，適用於高精度要求的工具機，除節流器與油墊結構參數外，公差設計對滑軌性能具有關鍵影響，本研究以一閉式液靜壓滑軌為載具，由該滑軌之剛性目標，探討其較佳之公差設計。 研究首先在滑軌油墊結構參數以及節流器參數固定的條件下，由負載及剛性與油膜間隙相關性分析決定合適的油膜間隙及其對應之尺度公差範圍。同時考量工作台精度與性能相關之關鍵尺寸，透過該滑軌之公差網路，進行公差分析與調配，然而調整後之公差規格過於嚴苛難以達成；研究進一步導入負公差配置法，以吸收組裝的精度變異，配置出可達成公差目標且能維持元件可實際達成的尺寸公差。 本研究之主要貢獻在於結合液靜壓滑軌性能設計與公差工程兩領域，文中不僅探討閉式液靜壓滑軌之間隙大小對於滑軌性能的影響，更近一步探討滑軌與油墊間之油膜傾斜度對於承載力與剛性影響；同時探討滑軌靜態與穩態滑動的性能表現，由滑軌之剛性設計訂定公差目標。在滿足性能與精度要求下進行公差調配，並應用負公差調配方法，配置合適可行之公差規格，除達成精度與剛性要求外亦降低加工需求。本研究結果可作為液靜壓滑軌考慮公差影響並進行設計時之依據。Hydrostatic slideways are widely employed in precision machine tools as it provides high stiffness, high damping and low friction. The design of its tolerances plays an important role in the performance of such a slideway. Based on the stiffness design, this study investigates the design, analysis and distribution of tolerances for a close-type hydrostatic slideway. The study started with deciding the dimensioning and tolerancing of clearance of such a slideway based on the analysis of clearance and stiffness under the conditions that the structure and capillary restrictors of each bearing pads remained the same. Furthermore, by considering critical dimensions related to both precision and performance of the slideway, tolerance distribution and analysis are conducted through tolerance network of the slideway under the error budget constraint. While the tolerance distribution are too small and not acceptable. An alternate approach named “negative tolerancing” is then applied to compensate tolerance accumulation. By doing so, a relatively practical tolerance range is reached which can be implemented compromising with the error budget and design target. The major contribution of this research is to develop an approach of tolerance distribution which fulfills the requirements of capacity and precision of a close-type hydrostatic slideway. This study not only explores the influence of the gap size of the close-type hydrostatic slideway on the performance of the slideway, but also discusses the effect of the oil film inclination between the rail and the oil pad on the bearing capacity and stiffness. This approach combines knowledge in both tolerance engineering and stiffness design of hydrostatic slideway. In the meantime, the negative tolerancing approach is employed to reach a more feasible tolerance specification which not only achieve precision and stiffness requirements, but also lower the fabrication cost. The results of this study can be used as the basis for the design of hydrostatic slideways.致謝 i 摘要 ii ABSTRACT iii 目錄 iv 圖目錄 vi 表目錄 ix 符號表 x 第一章 緒論 1 1.1研究動機與目標 1 1.2文獻回顧 2 1.2.1液靜壓支承研究 2 1.2.2公差分析方法 3 1.2.3公差調整與配置方法 4 1.3研究方法與步驟 4 1.4本文架構 5 第二章 液靜壓支承理論 7 2.1雷諾方程式的建構 8 2.2有限差分法解雷諾方程式 11 2.3流量平衡 14 第三章 滑軌間隙與傾斜度對閉式液靜壓滑軌性能影響探討 16 3.1矩形單向墊靜態性能分析 16 3.1.1單向墊壓力分佈 16 3.1.2單向墊承載力分析結果 19 3.1.3傾斜角度與油膜厚度對單向油墊靜態性能影響分析 21 3.2 液靜壓對向墊系統靜態性能分析 22 3.3矩形單向墊滑動性能分析 27 3.3.1單向墊壓力分佈 27 3.3.2單向墊承載力分析結果 31 3.3.3傾斜角度與油膜厚度對單向油墊滑動性能影響分析 33 3.4 液靜壓對向墊系統滑動性能分析 36 3.4.1上下順向滑動之承載性能 36 3.4.2上下逆向滑動之承載性能 38 3.4.3上順向下逆向滑動之承載性能 40 3.4.4上逆向下順向滑動之承載性能 42 3.5 公差對毛細管節流之雙平型閉式液靜壓滑軌剛性探討 43 第四章 閉式液靜壓滑軌之公差網路建構 47 4.1產品架構建立 48 4.1.1系統零件分解 48 4.1.2特徵分解 49 4.2公差堆疊分析 50 4.2.1公差網路建構 50 4.2.2力流分析 53 4.2.3公差分析之關鍵路徑 55 第五章 閉式液靜壓滑軌之公差分析與調配 60 5.1關鍵路徑之公差分析結果 60 5.2關鍵路徑之公差調整與配置 62 5.2.1公差貢獻度分析 62 5.2.2公差敏感度分析 63 5.2.3公差調整與配置結果 64 5.2.4負公差調配法 66 5.3工作台精度配置 68 5.4 公差分析與調配結果討論 73 第六章 結論與未來展望 76 6.1研究結論 76 6.2未來展望 77 參考文獻 7