Page 106 - Chalcogenide Glasses for Infrared Optics

84 Cha pte r T h ree

FIGURE 3.12 Diagram of an open down hole glass casting unit.

mold and controlling the glass temperature after it has been cast.
Using a system like this, TI, and later Raytheon, cast many tons of TI
1173 glass each year.

3.5 Purification, Compounding, Casting—One Closed
Operation
The changes made by the author in the TI glass casting process before
leaving were not major. For one thing, the glass was in production
and supplying orders for existing systems. Permission to make more
drastic changes proposed by the author was refused on the valid
grounds that changes could cause delays in deliveries.
When Amorphous Materials (AMI) was started in May 1977, such
restraints no longer existed. The fabrication of compounding cham-
bers with porous filters on a glass lathe had already demonstrated
improved purity. The drawback of the open casting system where the
escape of glass vapors changed the refractive index had been investi-
gated and the effect measured. The decision was made to combine
element purification, compounding the glass, and casting in a closed
sealed system into one operation. The first requirement was to recruit
the most skilled master glass blower available. Glen Whaley was such