Loose belts cause ringing and ghosting — the echo you see after sharp corners. Beginners almost always misdiagnose this as a speed or acceleration problem and tune the wrong thing for days.
Phase 0 — Mechanicalabout 10 min
How to do it
Find the tensioner on the X gantry and the Y axis.
Tighten until a pluck gives a clear low note — think bass guitar, not a slack rubber band.
Both sides of a dual-belt axis must match, or the gantry will not stay square.
Do not overtighten: excessive tension loads the stepper bearings and causes its own artefacts.
How to read the result
Plucked, the belt gives a low musical note rather than a dull slap. Deflection under a light finger press is small and equal on both sides.
Does your printer have this?
Nearly every printer has belts — look for a black toothed strap running along the X axis and, on a bed-slinger, under or beside the bed. What differs is whether there is a TENSIONER: a knurled wheel or a screw at the end of the axis you can turn to pull the belt tighter. Without one you tension by loosening the motor mount and sliding the motor, which is fiddlier but still this step. Mark this as absent only if you genuinely cannot find a belt on either axis — some very small or belt-free designs drive the axis another way.
Redoing this invalidates
Calibration is a chain. Change this and the results below were measured against the old value: