Diamond Turning of F-111 Windscreens: Feasibility Study Phase I

Abstract

Diamond turning of optics uses a single-point diamond tool on a precision lathe under precisely controlled machine and environmental conditions to fabricate an optical component. The technology has been used to make many high precision optics. The F-111 windscreen is in the shape of an oblique frustrated right circular cone, a geometry compatible with diamond turning. Phase I of the feasibility study demonstrated the machinability and polishability of the F-111 windscreen material. Two flat 15 cm square samples of the F-111 windscreen material were diamond turned and then polished. The diamond turning was performed on a Moore machine at Union Carbide's Y-12 plant. The Lawrence Livermore Laboratory polished the sample with Lustralox Plastic Grade on Polytex Supreme. Extensive pre-machining and postmachining tests are described, including the lateral shearing interferometric techniques developed by one of the authors. Optical distortion and haze were significantly reduced after machining and polishing. Diamond turning of windscreens may offer attractive cost savings by reducing shrinkage during fabrication and allowing recycling of windscreens rejected because of excess haze. Diamond turning may also provide revolutionary optical designs to reduce distortion through decentering techniques. The plans for phase II of the feasibility study, to machine and polish actual curved windscreen sections, will also be described.