I love it, probably the only thing missing is testing of ghosting/ringing on corners, so maybe an addition of a square item to the mix?
Circles are ovals = tighten belts, ???
Walls are lumpy = flow rate too high, ???
You are awesome. Just adjusted my belts and my ovals turned to circles! YES!!!!
Looks useful. As a new 3D printer owner, I have to ask - what in particular do you look for, and what do you do based on what you see?
Print with 100% infill. The solid circle will serve the purpose of a calibration cube to help you dial in your flow rate. The one that's closed only on the top tests bridging, and the one that's open at both ends tests thin walls to see if you can print small features accurately with your layer height and thread width settings. Also, if they're not round, you know you have backlash.