｜環形刀具均勻化拋光之研究

摘要：均勻化拋光法是將環形刀具在z軸加裝旋轉軸；使刀具旋轉能均勻拋光刮痕方向，而獲得更光滑的工件表面。

英國Zeeko公司提出類似陀螺運動的進動式（Precessions）拋光而成功地獲得Ra 0.5 nm的光滑表面。本文參考Zeeko公司的進動拋光方式，在刀軸部份加裝z軸旋轉臺（類似進動軸），產生兩個旋轉動作而進行環形刀具均勻化拋光。

由均勻化拋光的實驗結果證明可成功均勻先前環形刀具拋光所產生的刮痕，並得到具有對稱性加工深度分佈與良好的加工重現性，在工件獲得表面粗度Ra 6.7 nm的鏡面拋光結果。

Abstract: The ring shaped tool uniform polishing is investigated in this thesis. The uniform polishing process is equipped with an additional rotating table along the z axis, and then averages the direction of scratch mark during the polishing.

The Zeeko Company in UK proposed the Precessions process which is similar with the rotating gyro, to fabricate the precise aspheric lens in a 7 axes machine. The result proves that the processions can effectively reduce the surface roughness and produce a perfect mirror surface on glass BK7 with the surface roughness of Ra 0.5 nm. .

Referring to the successful Processions process, the extra rotating axis is attached onto the original tool spindle to compose the uniform polishing. That is, the additional rotating axis is perpendicular to the former tool spindle for averaging the scratching marks in the uniform polishing process

For the uniform polishing process, the experimental result reveals that the tiny tool marks has been reduced by using the uniform polishing process. This new process also generates the symmetrical distribution of depth and perfect machining repeatability. Finally, the work was polished and yielded the surface roughness Ra 6.7nm.

關鍵詞：環形刀具、表面粗度、重現性、刀具磨耗、均勻化拋光

Keywords：Ring Shaped Tool, Surface Roughness, Reproducibility, Tool Wear, Uniform Polishing

緒論
隨著科技的進步，對光學元件功能的需求也隨之提高，例如需要更精確的聚焦和解析能力。而這些光學性能又與形狀精度（Form accuracy）有關，因此對於光學元件形狀精度的要求也更精確。例如目前普及化的視聽產品DVD（Digital Video Disk）播放機中，其核心關鍵組件光學讀寫頭形狀精度的要求，希望能提高到0.1μm以上。亦即希望此光學元件的形狀誤差能降低到0.1μm以下。形狀精度是指所設計加工的表面輪廓（Surface profile）在進行加工後所獲得表面輪廓之間的誤差。如鑽石車削或精密輪磨加工時、刀具路徑應該是沿著所要的形狀曲線移動，但是因為加工時機器振動的干擾及變動的反作用力也經由刀尖傳遞至刀具，而影響刀具的定位精度，使得加工後產生形狀誤差。例如在切削或輪磨過程時、而傳統加工法如輪磨（Grinding）和鑽石車削（Diamond turning）所能達到的形狀精度已不敷所需，而精密拋光是模具的最後一道加工。因此為了降低工件的形狀誤差，更進一步提昇工件的形狀精度與附加價值，而發展精密拋光（形狀誤差補償）加工法是迫切需要的。本研究針對環形（Ring shaped）刀具均勻化拋光（Uniform polishing）的加工特性。其中環形刀具拋光是以刀具軸向曲率半徑不因磨耗而改變的特性，達成確定性（Deterministic）加工的目的；而均勻化拋光則是在環形刀具拋光加工機的z軸加裝旋轉軸；使增加旋轉運動的刀具能均勻拋光刮痕方向，而獲得更光滑的工件表面。