Just made this to pinpoint any issue with my Prusa Mendel. It should work to test out any machine (in theory of course).I created a 140mm one (since my calipers only go to 150mm) to check my Prusa Mendel, but I made one at 90mm too for the MakeBots out there.The circle (which is half the size: 140mm object = 70mm circle) should be pretty hi-res so you can check if your belts are loose and stuff.This also helps check the level of your build platform.I used this object to really fine tuning my printer and seems to get things more accurate when measuring a printed object than just the carriage movements.Print it out and measure. --- X & Y should measure to either 140mm or 90mm --- Z should be 30mm (the tower in the middle) --- The circle (outer diameter) should measure half the total size of the object you chose (70mm or 45mm) --- Measure the consistency & thickness of the outer edge to find any issues with your build platform.