Conformal windows and freeform optics are becoming more widely used. Conformal window/freeform optics have a geometry that is non-rotationally symmetric. These optics improve aerodynamic performance by matching the mold line of the design, enabling more complex systems, and reducing the optical system footprint. Freeform and conformal window geometries are becoming more complex to increase their design benefits and, with tighter tolerances on the surface geometries, new challenges in manufacturing are being realized. From part design to the manufacturing process to metrology of the surfaces, each stage plays a role in whether the part is made successfully. In design, a good datum structure should be chosen for repeatably and accurately locating the part in the manufacturing and metrology machines. Careful consideration to stresses being induced in the part during the fixturing process is required to minimize part springing and the associated form error changes when removing the part after machining is complete. As part geometries have evolved in complexity and sensitivity to error map alignment has increased, a 3D error map is crucial to making error alignment easier and less prone to mistakes. Just as important as the freeform surfaces, but often not focused on as much, is the quality of the edges of the part. High quality edges are critical to prevent breakage and chippage propagating out from the edges. This paper presents keys and best practices for manufacturing freeform and conformal geometries to ensure the greatest chance of meeting the required tolerances.
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