UPDATED VERSION: Spinning Spherical Fidget Toy

I really enjoy designing unique fidget toys that can be printed in place in one shot on my Mini+. These toys serve no purpose other than they are fun to play with, expand my design skills using Shapr3D and really push the boundaries on what you can print on the Mini+. This latest design is a spinning sphere within a sphere. You can see the sphere isn't solid. Solid spheres don't print well on 3D printers (the bottom of the sphere never prints well).  I designed the spheres with blades like a spherical turbine and the knob at the top allows you to spin the inner sphere while the outer sphere stays in place. It's actually amazing how well it prints with no supports at all. The only issue is a bit of stringing that can be brushed off with your finger after the print it done. The zigzag band around the centre of the spheres gives the the blades in the spheres a bit of stability while printing the blades at the top half of the model.  

Print at 100% or larger and increase the infill to 40%+ to provide more strength for the blades and inner spindle.  I also print using a brim and don't bother with supports.  Supports are completely unnecessary.  After printing, you can use a small screwdriver (see photo) to unstick the spindle from the top and bottom of the outer sphere.  You a then use that same screwdriver to gently pry/spin the inner sphere in order to get it moving.  A little lubrication on both top and bottom bearing points let's it spin longer.

I would love to see someone with an MMU print this model with two different materials for the inner and outer sphere.  I've provided some 3D rendered photos from Shapr3D to show you what it would potentially look like with two different materials.  

Let me know what you think. This was a fun design project that took some very careful thinking and design considerations to get the Mini+ to print the model smoothly without supports.  

UPDATE:  I made some changes to the clearances on the two bearings to make it easier to separate the inner and outer spheres after printing.  I also increased the thickness of the zigzag band and widened the diameter of the centre spindle to prevent the top knob from breaking off when you try to separate the two spheres.  You can now print it at 15% infill and it works just fine.  Faster printing and less material.  The photos printed in pearl white are the new version.