What ghosting is and how to confirm it
Ghosting, also called ringing or echoing, comes from vibration. When the print head stops and changes direction at a corner, its momentum makes the head, belts and frame oscillate for a short time. The nozzle traces that oscillation into the wall as a series of fading ripples. They appear right after features such as corners, embossed letters or holes.
Confirm it by printing a ringing tower or a cube with embossed letters. Look along the direction of travel: ghosting appears as evenly spaced ripples after each sharp feature, getting weaker with distance. If ripples show on all walls with no link to features, the cause is more likely Z banding or extrusion variation.
Two more checks help. First, note which walls show it: ripples on walls parallel to the X axis come from Y-axis vibration and the reverse, so you know which belt and which motion system to inspect. Second, measure the distance between ripples. Dividing the print speed by that spacing gives a rough resonance frequency; for example, ripples 2 mm apart at 80 mm/s suggest about 40 Hz. That number is useful if your firmware supports input shaping, and it is a good way to tell whether a change actually moved the resonance or just hid it. Keep the test print the same between changes so results are comparable.
Causes, most likely first
- Speed and acceleration too high for the machine.
- Loose belts that act as springs.
- Loose frame, gantry or hotend mount.
- Heavy moving mass, such as a heavy bed on a bed slinger or a heavy toolhead.
- Soft or wobbly table under the printer.
- No input shaping or poorly tuned shaping on firmware that supports it.
Fixes, cheapest and fastest first
1. Lower acceleration
Acceleration has more effect than speed. On a typical bed slinger without input shaping, try 500 to 1500 mm/s² for outer walls. Many slicers let you set lower acceleration for outer walls only, so overall print time barely changes.
2. Lower outer wall speed
Print outer walls at 30 to 60 mm/s while keeping infill faster. Also check jerk or square corner velocity; values around 5 to 8 mm/s are a safe starting point.
3. Put the printer on a solid surface
A heavy table, a concrete paver or a thick wooden board under the printer reduces vibration. Soft rubber feet can help or hurt depending on the machine; test both.
4. Tension belts and tighten the frame
Belts should be firm with a low twang. Tighten frame bolts, the hotend and fan shroud mounts, and adjust eccentric nuts so wheels have no play.
5. Tune input shaping
If your firmware supports it (Klipper, recent Marlin, many newer printers), run the built-in resonance calibration or print a ringing test and set the shaper frequency for X and Y. This usually removes most ringing while allowing higher accelerations.
6. Reduce moving mass
Swap a heavy glass plate for a thin steel sheet, and secure loose cables that whip around.
Material notes
- PLA: hard and glossy, so ringing is very visible.
- PETG: shows ghosting similarly; lower outer wall speed helps gloss and ringing at once.
- ABS: slightly softer finish but same mechanics; enclosures do not change ringing.
- TPU: printed slowly enough that ghosting is rarely an issue.
Prevention checklist
- Keep outer wall acceleration and speed modest.
- Check belt tension and frame bolts periodically.
- Run input shaping calibration after hardware changes.
- Keep the printer on a heavy, stable surface.
- Use a light build plate where practical.
- Print a ringing tower when trying new speed profiles.