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Proceedings Paper

Mandrel reusability in precision replication of ZnS conformal domes
Author(s): Jitendra Singh Goela; Joel Askinazi; Barry Robinson
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Paper Abstract

Recently precision replication of flat, spherical and aspheric surfaces was demonstrated in ZnS by a chemical vapor deposition (CVD) process. Two-inch size ZnS parts were replicated successfully down to a fraction of a wave in the visible and finish of 20-180 Angstroms RMS. The replication technology was then extended to produce six best-fit-sphere ZnS corrector elements of diameter 2.4-inch by replicating on Al2O3 and SiO2 coated, highly polished and diamond turned ZnS mandrels. These replicated corrector elements measured an inside surface figure of 0.14-0.27 Angstroms RMS and smoothness of about 41 Angstroms RMS. Mandrel reusability was then demonstrated by replicating on several previously used corrector element mandrels which were minimally refurbished (mandrel surface was cleaned with acetone). These replicas and mandrels measured essentially same surface figure and smoothness after second replication as before. After replication, analysis was performed on a few mandrels, which did not release from the replicas. Cause of this adherence was determined to be presence of 10-20 micron size pinholes in the release coating. Very good replication was achieved on those areas where no pinholes were present. The integrity of the release coating determines the durability of the replication mandrel.

Paper Details

Date Published: 7 September 2001
PDF: 14 pages
Proc. SPIE 4375, Window and Dome Technologies and Materials VII, (7 September 2001); doi: 10.1117/12.439167
Show Author Affiliations
Jitendra Singh Goela, Rohm and Haas Advanced Materials (United States)
Joel Askinazi, BFGoodrich Co. (United States)
Barry Robinson, BFGoodrich Co. (United States)

Published in SPIE Proceedings Vol. 4375:
Window and Dome Technologies and Materials VII
Randal W. Tustison, Editor(s)

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