Spin casting (mirrors)
Spin casting is a technique for constructing large parabolic mirrors by using the curved surface formed by a rotating liquid (e.g. in a rotating furnace). It is distinct from the spin casting or centrifugal rubber mold casting (CRMC) technique used for casting metal or plastics.
The term is applied to the fabrication of large telescope mirrors, where the natural paraboloid curve followed by the molten glass greatly reduces the amount of grinding required. Rather than being cast by pouring glass into a mold (with top and bottom) an entire turntable containing the peripheral mold and the back pattern (a honeycomb pattern to lighten the finished product) is contained within a furnace and charged with the glass material used. The assembly (or rotating furnace) is then heated while spun at slow speed until the glass is liquid, then gradually cooled over a period of months.
- "Optical Fabrication in the Large" (PDF). p. 6.
- Optical Fabrication in the Large, p. 6
- Spin-cast Zerodur mirror substrates of the 8-m class and lightweighted substrates for secondary mirrors
- An investigation into the spin casting process
- A Telescope Made of Moondust including a citation to 1966!
- Wonderings On Spin Casting Parabolic Mirrors
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