Study of optimum tool change time in v-groove roller turning

增亮膜為背光模組之ㄧ重要零組件，目前製作方式乃是利用滾筒模具壓印技術在高分子材料上複製出v型微結構。為達到良好的增亮效果，滾筒表面微結構具有 μm的尺寸公差，v溝的斜面則必須維持在鏡面的狀態。滾筒模具是以鑽石刀具超精密車削的技術製作，在現今大尺寸的面板與滾筒模具數量倍增的需求下，滾筒的直徑變大而長度遽增，使得刀具車削的距離變長，於長時間加工的過程中，刀具可能會發生微崩落(chipping)或是磨耗(wear)的現象而無法製作出滿足表面精度需求的滾筒，嚴重的狀況下甚至造成工件的報廢；因鑽石刀具價昂，在堪用的狀態下不會丟棄，而車削新的滾筒工件時即採用全新的刀具。目前滾筒車削的生產線上多以目測法判斷工件的表面狀況，以決定是否需要更換刀具，尚未有自動化判斷換刀時機的方法，而更換後的新刀具尚須經繁瑣的對位程序。本研究提出以機器視覺直接取得工件表面的亮度，經過色彩空間轉換將光度量化，並且訂立標準閥值，當光度值低於閥值之下，代表滾筒模具的表面亮度不符需求。實驗結果證實工件表面呈現非鏡面時，亮度值低於240需要更換刀具。文中亦以影像處理方法尋找刀具退縮量，除了可以提供作為刀尖於徑向的補償外，亦可以用於更換後刀具的定位，使其與原刀具的位置吻合，以繼續進行車削完成大尺寸的光學滾筒模具。Brightness Enhancement Film (BEF) is one of the most important components in the Back Light Unit. The v-groove configuration of BEF is duplicated from the roller by roll-to-roll process. In order to enhance the luminance of the light source, the microstructure of the v-groove has to maintain two requirements which are form error for μm and mirror surface. The roller is cut by the ultra-precision diamond turning tool. To meet the current requirements of manufacturing larger size of LCD (Liquid Crystal Display), the roller has to become longer and larger in size. Hence in consequence the cutting distance becomes much longer and accompany the problems of chipping and wear of cutting tools for the long time tooling, indeed, roller is no usable. Furthermore, the diamond tool doesn’t been discarded arbitrary because it is very expensive. At present there is no other way for most manufactures except by naked eyes to estimate whether it is the time to change the tool. Moreover estimating with human eyes cannot accurately decide the critical point of surface brightness and is also ineffectual for automatic manufacturing. Thus an optimum method to estimate the time to change tool is developed in this research by quantification of the brightness from work surface, setting an experimentally determined threshold value of 240, i.e., as the brightness value is under 240 the tool has to be changed. As far as the tool is changed the developed system would determine the diamond tool tip shrinkage for follow-up compensation by machine vision in order to match the position of the new tool tip after reinstallation with worn tool position before detachment. This process allows the roller to turn continuously and finish fabrication.誌謝 i要 iibstract iii錄 iv目錄 vii目錄 ix一章 緒論 1.1 鑽石刀具切削技術背景 1.2 鑽石刀具切削滾筒模具及瓶頸 2.3 研究動機與目的 4.4 文獻回顧 5.4.1影像處理之邊緣檢測 5.4.2應用機器視覺與影像處理技術於線上檢測 5.5 論文架構 7二章 理論基礎與方法 8.1 數位影像處理 8.2 影像濾波： 9.2.1 影像平滑化(image smoothing) 12.2.2 影像銳利化(image sharpening) 13.3 影像處理之邊緣檢測 14.3.1 微分運算子 15.3.2 Sobel 邊緣檢測運算子 17.3.3 Canny 邊緣運算子 18.4 數位顯示與色彩空間 22.4.1 RGB與YUV之色彩空間轉換 23.5 刀具退縮量之量測方式 24三章 實驗規劃及實驗儀器 26.1 實驗架構 26.1.1 機器視覺影像擷取系統 26.1.2 實驗規劃與誤差靈敏度分析 28.2 實驗儀器 31.2.1 感光元件以及鏡頭規格 31.2.2 儀器架設以及線性校正 35四章 實驗與成果討論 38.1 論述 38.2 光源定義 38.3 亮度實驗 39.4 轉動時亮度量測 46.5 刀尖退縮量量測實驗 48.6 討論 49五章 結論 51.1 小結 51.2 未來展望 52eference 53者簡歷 5