Improved model stands for Openscan Mini turntable

Made three changes but kept overall dimensions:

- thinner shaft as stock was thick enough to rub on the rotor during operation
- Angular keyed cutouts for the stepper motor shaft to fit into, which should stop spinning in place.
- better fillets as the stock ones were kinda abrupt and ugly (!) this should also strengthen the transition areas between slopes.


Supplied in 3MF and STL, 3MF models have some tweaks and improvements, I'm only putting STL here as Thingiverse forces it.

TIP: Print One test first to see if you need to scale model up/down in your slicer to get a good fit. My prints as-is with a little force to get on and a satisfying "pop" when you pull off.