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14 September 2018 Manufacturing of a large, extreme freeform, conformal window with robotic polishing
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Abstract
As aircraft design advances, the requirements on the aerodynamics of such aircraft become much more stringent. The use of conformal windows on such aircraft enables better aerodynamics by eliminating the need for protruding sensor packages, thereby reducing the aerodynamic drag across the airframe. However, manufacturing conformal windows to optical specifications is difficult due to the extreme freeform shapes required for these aerodynamic design forms. Optimax has developed a robotic form correction platform designed specifically to manufacture extreme freeform optical surfaces over large areas.

This presentation will outline the manufacturing process by which a 330 mm square conformal window was created with 123 mm of sag, 98 mm departure from a best fit sphere, and a nominal 23 mm thickness. The surface specification was given as <0.5 μm RMS surface irregularity over the clear aperture. Fiducials were designed into the part to ensure accurate form generation and measurement.

Both sides were generated and the fiducials created using a commercial 5-axis ultrasonic grinding machine. The initial fiducials were determined to be inadequate and resulted in excessive and unrepeatable tilt in subsequent measurements of the generated surfaces, new fiducials were created, resulting in tilt less than the measurement uncertainty of the CMM used for the metrology. After generation, a custom robotic form correction platform based off of an industrial 6 degree of freedom robotic arm was used to polish both surfaces.
Conference Presentation
© (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Daniel R. Brooks, Matthew Brunelle, Timothy Lynch, and Kate Medicus "Manufacturing of a large, extreme freeform, conformal window with robotic polishing", Proc. SPIE 10742, Optical Manufacturing and Testing XII, 107420L (14 September 2018); https://doi.org/10.1117/12.2321157
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