It is critical to maintain the full-hard temper at the flexing edges of the fan blade. Cutting the sheet with heat destroys the temper. Heat treating fans after cutting is not possible because thin sheets of steel warp in the heat treating process. However, I understand that the razor blade industry has perfected this process. Cutting the fans by stamping is problematic. Firstly, the steel sheets are extremely hard and would damage a stamp quickly. Also, the shearing process introduces micro-cracks into the edge, which is a further crack nucleation point. This can be mitigated in a post-processing step. Pulling the sheet through a die creates longitudinal scratches on the edge of the sheet. These longitudinal scratches do not concentrate the stress when the sheet is flexed.
Photoetch cutting the sheets was chosen. This was performed by Precision Micro Ltd https://www.precisionmicro.com/ . They can process a sheet on the scale 1m^2 and can be supplied a DXF file with the laid out fans. They add tabs that keep the fans loosely attached to prevent them falling out during processing. It is important that these tabs are not placed on horizontal edges of the fan blades, which would act as stress concentration sites. The cold-rolled steel should only be flexed perpendicular to the direction of the cold-rolling, so the orientation of the fans on the sheet is important.
Accelerated testing of the fans was performed on the photo-etched sheets without further processing. I did experiment with perfecting the edges further by electropolishing. If endurance is required in the years to decades range, I suspect electropolishing and coating the edges is a prudent precaution.