Test Sphere 2
thingiverse
Test Sphere 2 might actually function; I just haven't had a chance yet to thoroughly examine its printing capabilities.
Download Model from thingiverse
With this file you will be able to print Test Sphere 2 with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on Test Sphere 2.