Improved Callibration Cube

This calibration cube allows you to measure your printer's dimensional accuracy better than the original. 

The original calibration cube with sharp corners can lead to lousy calliper measurements, especially if you are printing very fast, because of ringing/ghosting. Rounded corners reduce angular acceleration so that the printer doesn't overshoot the corners, and you can accurately adjust your stepper motors' steps/mm. Chamfer on the bottom Z face to prevent elephant's foot from potentially messing up caliper measurement.

X and Y are labelled on only one side each, and Z is not labelled because it can be inferred. More smooth faces = less ringing and more accurate calliper measurements.