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.