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Proceedings Paper

Computer control and process monitoring of electrolytic in-process dressing of metal bond fine diamond wheels for NIF optics
Author(s): Richard J. Boland
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Paper Abstract

Deterministic grinding of large optical components (2600 - 3700 cm2 area) using Electrolytic In-Process Dressing (ELID) requires strict process controls for several process parameters. In this paper we describe how the voltage and current characteristics of the ELID circuit may be used to establish viable, in-situ feedback monitoring of the grinding process. The specific approach used was to keep the ELID power supply in constant voltage mode and maintain an average power level that was optimized for each material. This was accomplished by monitoring the pulsed waveform and its frequency spectrum. By controlling the down feed rate it is possible to control the electrical characteristics of the wheel. A control loop was developed to over-ride the feed rate based upon the characteristics of the pulsed waveform. A second ELID process monitor was incorporated into the optic support scheme. To insure the part being ground was in a mechanically stable environment the optic was instrumented with eddy current gauges to detect motion during machining. Based on the data obtained from these sensors the support for the optic was optimized to minimize rigid body motion as well as bending. It has been found that creating a stable platform for machining as well as maintaining control of the ELID system is essential for a deterministic process.

Paper Details

Date Published: 11 November 1999
PDF: 9 pages
Proc. SPIE 3782, Optical Manufacturing and Testing III, (11 November 1999); doi: 10.1117/12.369234
Show Author Affiliations
Richard J. Boland, Zygo Corp. (United States)

Published in SPIE Proceedings Vol. 3782:
Optical Manufacturing and Testing III
H. Philip Stahl, Editor(s)

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