CalibrationCube for flowrate calibration

I had major problems with the print quality when it comes to infills, or sharp perimeter turns. The infills were printed bumpy, and my nozzle plowed through or rattled over them. Furthermore, the second extruder's nozzle bumped also against the print when it crossed the infills.

The guys at Maker's Tool Works said that I have a flow rate issue most likely, i.e., my flow rate is too high. It has surprised me since I calibrated my extruder as Thomas Sanladerer explained at YouTube (https://ww