Computer numerically controlled plasma chemical vaporization machining with a pipe electrode for optical fabrication

We have developed a chemical vaporization machining device that has computer numerically controlled plasma, by using a pipe electrode for optical fabrications. In this device, less than approximately 1 atm of pressure, plasma is generated around the tip of a pipe electrode. During the process, a workpiece is scanned against the electrode under computer control to achieve the desired shape to be removed. A workpiece of silica glass plate is shaped by use of this device, and the removal characteristics of the device are examined. The equations to characterize numerically the shape resulting from scanning of a workpiece have been derived. The new device allows the high precision of optics from the micrometer to the nanometer level with high-speed removal. The shaped surface is sufficiently smooth to be suitable for optical use.