<title>Pad polishing for rapid production of large flats</title>

Abstract

Pad polishing is an efficient technique for polishing-out a ground surface and reaching a figure better than one wave, ready for completion with less than an hour on a planetary polisher. Recent work has shown success on 350 mm square parts; current work involves scaling the process to 1.4 meter diameter. For the 350 mm square piece of BK7, removal was one micrometer every 10 minutes. Polishing-out from a 5 micrometer grind took less than 3 hours, to a surface smoothness of one nm rms. Other tests verified that the pad leaves no unusual subsurface damage. Following completion on a pitch planetary polisher, surface finish is the same as obtained for conventional processing.