Ghosting is the wavy echo pattern you see following a sharp feature (text, corner, hole) on a vertical wall. It's caused by mechanical vibration: the toolhead changed direction faster than the printer's frame could absorb, and the structure rang like a tuning fork. Modern firmwares solve this with input shaping , but a well-tensioned printer with the right acceleration limits beats input shaping on a loose printer every time.
Three things, in order: (1) Tighten the belts — loose belts can't transmit the motion cleanly. (2) Bolt the printer to a heavy, rigid surface (concrete paver, granite slab, or solid IKEA tabletop). (3) Run input shaping calibration on Bambu (auto), Prusa MK4/CORE One (auto), or Klipper ( SHAPER_CALIBRATE ). Then lower acceleration in your slicer to the printer's tuned value (usually 5,000–10,000 mm/s²).
When the toolhead changes direction (going around a corner, starting a new perimeter, finishing a hole), the motor instantly accelerates the head in a new direction. The frame — not perfectly rigid — flexes and then rebounds. That rebound prints as a visible wave on the next ~5–20 mm of wall.
The frequency of the wave is the printer's natural resonant frequency on that axis. Typical values:
The slower the resonant frequency, the more visible ghosting becomes (Y on a heavy bedslinger is always worst).
Print a calibration cube or any small object with sharp corners. Look at:
For a numerical reading, mount a phone-app-based accelerometer on the toolhead and run the Klipper resonance test. Bambu and Prusa MK4 do this automatically.
Loose belts cause ringing. The same belt also dictates what input shaping can compensate for. Always start here.
See Belt tension and calibration for the full procedure.
The frame and what it sits on dictate the resonant frequency. To raise it (which makes ghosting less visible):
Input shaping is a motion-control algorithm that anticipates the resonance and shapes the velocity profile to cancel it. It is the difference between 5,000 mm/s² printing with visible ringing and 10,000 mm/s² printing without.
If input shaping isn't available or you've maxed it out, lower acceleration in the slicer to whatever produces clean walls. Test at:
The acceleration value that produces clean walls is your real limit. Anything above is just heat in the steppers and noise in the room.
"Jerk" in Marlin and "square corner velocity" in Klipper is the maximum velocity change the printer takes without decelerating. Set too high and corners ring. Recommended: