Summary

My wife has relatively small hands and has difficulty in removing the blades from the 100 mm diameter cup after blending her favourite smoothy.
The ones I have found use the motor activation lugs to grip the cup and stop it from turning.
I feel that these are rather fragile so i designed one that grips the 4 ribs on the outside of the cup. I my view, this is a far more robust solution as it spreads the forces over much larger areas and should therefore lead to less chance of damaging the cup.
The design is scales to suit my particular printer but you can scale it on the XY plane if you find it to be either too tight or too loose depending on your printer calibration.
So far I have only printed it in PLA+ but intend printing another one that can go in the dishwasher with the rest of the Nutribullet parts.