Dunno if I qualify as an "engineering GURU, NABOB and POTENTATE" but here's my 2psi
It is possible to accurately 3D CAD model the diaphragm and then generate a 3D printed SLA master that can be used to make up a silicone rubber mould for very low volume runs (10-30 depending on complexity).
I've used this process at work before, but only on prototyping relatively thick walled corrugated elastomer cable routing elbows to a powered liftgate.
https://www.3dsystems.com/on-demand-man ... graphy-sla
'From product development models and prototypes to low-volume production runs, this rapid prototyping process allows us to produce parts that accurately mimic the color, texture, feel and physical properties of injection molded parts.
Accurately mimic production colors and textures
Large material selection – rigid, flexible, durable, clear and high-temp
Offers similar physical properties to injection molded parts
Used for pre-production runs
Parts made for marketing samples and test prototypes
3D Systems now make a range of Urethane rapid prototyping materials in soft flexible 25-50 Shore A hardness.
https://www.3dsystems.com/on-demand-man ... /materials
Quite a few places now offer this service:
https://www.stratasysdirect.com/technol ... ne-casting
https://schmitprototypes.com/services/r ... g-casting/
HOWEVER, the wall thickness on a typical diaphragm is around 0.5mm and could be difficult to fill consistently with the vacuum cast urethane process.
The other consideration is that cast urethane has pretty much unknown performance under repeated flex cycles vs liquid silicone rubber (LSR) which modern injection moulded high performance diaphragms are made from... but also need to be heat cured as part of the process.
For SCUBA usage I'd also want any cast urethane material to be food grade to limit any issues in contact with air going into your lungs