桌上型雙主軸超精微CNC 工具機開發與細胞鏡檢模仁製作研究

Abstract

本研究旨在設計並開發一部「桌上型雙主軸超精微CNC工具機」，主要目的是以此部超精微工具機發展「精微模具」的製造技術，特別是在延性材料如模具鋼或硬脆材料如矽晶圓及光學玻璃等工件上，開發細胞鏡檢晶片的模仁之技術。由於細胞鏡檢晶片具極精細的溝槽結構，所以「桌上型雙主軸超精微CNC工具機」設計成龍門式結構(Gantry framework)，並進行受力承載與顫振分析，以建構高剛性及高勁性的工具機，防止加工過程中，結構發生變形而影響加工精度。為減少工件夾持與翻轉校正時間，及設計適於精微模具的製作技術，維持高精度加工，本研究提出「雙主軸」工具機的設計，即工具機上設計可裝置互相垂直的「成對」刀具、工具與量具，以便同時或依序精密加工工件。為此，本研究於開發的工具機上，建構線式放電研削、高速研削、拋光與量測等技術，用於線上精微刀具開發、線上精微模具製作與線上精微拋光等工作。透由線上放電成型技術，本研究能將含硼聚晶鑽石輪刀的切刃，精細加工至5 µm厚度。為成型細胞鏡檢晶片模具之精細溝槽結構，研究中，亦提出一種「高速快淺研削技術」，即裝置於臥式軸上的鑽石輪刀，經線上放電薄化成型後，不做拆卸，直接移位至NAK80模具鋼上，進行陣列微溝的成型研削。高速快淺研削之進給切深，被嚴謹控制在奈米等級的超薄去除量，並加快研削速度，以提高單位時間之金屬移除率。經系列實驗證實，奈米切深能使鑽石輪刀順利地對NAK80模具鋼進行成型研削，並成功開發出槽寬8 µm的陣列微溝，微溝表面粗糙度達Ra10 nm以下。因鑽石輪刀被線上成型且無拆卸，故輪刀能以主軸原始精度進行陣列微溝研削，並獲致極高穩定度的研削效能與研削精度，大幅省卻繁瑣校正時間。研究發現，在多道次微溝研削後，鑽石輪刀仍能維持其切削力，證實奈米切深能使輪刀上的每顆鑽石磨粒因極少的材料移除量，而處於常溫加工，能有效減緩鑽石中的碳原子與鐵原子之親和速度，所以材料移除機制仍容許輪刀以SP3的鑽石結構，對模具鋼的鐵原子進行差排剪切。完成之細胞鏡檢晶片模仁亦不拆卸，直接切換成立式軸，進行線上精拋加工，同時移除陣列微溝毛邊。晶片模仁經精密塑膠射出成型及產學合作之細胞鏡檢公司臨床實驗後，證實此項新開發的塑膠鏡檢晶片已達商業化水準，說明本研究所開發的精微製造技術與雙主軸超精微CNC工具機，完全能提供開發精微模具，特別是生醫模具所需之精微製造技術，此項研究深具商用價值。

The primary purpose of the thesis is to develop a tabletop dual-spindle ultra precision CNC machine tool and using the finished machine tool to fabricate crisscross microgrooves on ductile material as NAK80 steel and on brittle material as optical glass. This developed technology can be applied to the fabrication of biomedical chip mould for the microscopy examination chip of cells of urinary sediments. The tabletop CNC machine tool is designed with gantry framework to possess high system stiffness for precisely machining the microgrooves on the mould steel. A dual-spindle design which two tools are mutually perpendicularly mounted on the developed machine tool is proposed and four technologies including micro EDM, grinding, polishing and measurement are constructed respectively on the machine tool to in-situ fabricate the micro chip mould. The on-line WEDG method verifies that the boron-doped PCD can be thinned down to 5-µm in edge-thickness on the developed machine. The thinned wheel-tool is then directly positioned on the mould steel to generate multiple microgrooves on-line. A technique called High Speed and Fast-Shallow Grinding (HSFSG), which utilizes a very high machining speed, a fast feed rate, and shallow depth grinding, is employed to effectively generate precise microgrooves of high integrity. Experimental results show that the width of the grooves in the array is 8 um and a surface finish of Ra equal to 10 nm is simultaneously achieved on the mould steel. The wheel-tool fabrication and microgroove generation are carried out on the same machine, decreasing vibration occurring and guaranteeing machining accuracy. In addition, the sharpness of grinding edge of boron-doped PCD can be kept for a long time. Due to a very shallow grinding depth used results in cold machining. This can prompt diamond grain working at SP3 bond structure, reduce the affinity between iron and carbon atoms and then retard the tool wear as a result of cold processing although the grinding object is carbon steel. The surface of the chip mould is then directly polished to remove the burrs at the microgrooves after switching to the vertical polishing tool. The finished chip mould has been successfully employed to fabricate the biochip by micro injection and then it is used to the clinical trial stage. This study demonstrates that the tabletop dual-spindle ultra precision CNC machine tool has been successfully developed and the micro technologies can be really utilized to the fabrication of biomedical chip mould. It is expected that the technique will contribute significantly to the bio-medical field.