Ringing and ghosting after sharp corners: input shaping, acceleration and belt checks

Prusa recognizes ghosting as several waves that follow a sharp edge of the model ^[4]. Klipper calls the same defect ringing, echoing or rippling: edges repeat themselves on the surface as a faint echo because the printer keeps vibrating after a quick change of direction ^[1]. Because the waves come from the motion system, the fix splits into mechanical work, which raises or cleans up the resonance, and input shaping, which cancels what is left.

Confirm it is ringing

Ringing runs along the wall right after a corner or other sharp feature ^[4]. That separates it from two look-alikes:

• Z-banding shows as horizontal stripes that repeat with height regardless of corners. See Z-banding.
• Ripples that depend on wall speed rather than on corners. OrcaSlicer’s Resonance avoidance option slows outer walls out of the printer’s resonance speed range, and the wiki pairs it with a separate VFA speed test ^[12].

Klipper adds a direct test: on its ringing tower, true ringing follows the pattern of the curved notches. If it does not, the defect has a different mechanical or extruder origin and should be fixed before tuning input shaping ^[1].

The ripple spacing also tells you the frequency. Klipper’s formula is f = V × N / D, where V is the outer-wall speed in mm/s and N is the number of oscillations counted over a distance D in mm. Its example, 6 oscillations over 12.14 mm at 100 mm/s, gives about 49.4 Hz ^[1].

Symptom, likely cause, what to check

Mechanical checks before tuning

1. Belts. Prusa ties loose belts to ghosting, layer shifts and out-of-round circles ^[6]. Its ghosting article suggests plucking the belt for a deep bass tone and, on the MK3 family, reading Belt Status values, where 240–300 is fine and a lower value means more tension ^[4]. Bambu Lab models the belt as the spring and the gantry as the mass, with a natural frequency of f = √(k/m); a loose belt lowers k and the frequency, which affects vibration compensation ^[8].
2. Guides and rods. Bambu Lab recommends cleaning X1/P1 carbon rods when ribbing or vibration artifacts appear on outer walls, and routinely after every 5 kg of ABS or ASA ^[10].
3. Support surface. Prusa notes that ghosting can appear even with correct belts, grows with print speed, and that a firm surface helps ^[4].
4. Loose parts. Prusa’s vibration article for the MK3S+ lists loose heatbed screws, loose LCD screws and misaligned Y rods among the sources of rattling and vibration during moves ^[7].

After belt or rod work, recalibrate: Bambu Lab says both change the toolhead’s resonance characteristics ^[8], and Klipper lists belt tightening among the changes that shift ringing frequencies ^[1].

Input shaping by firmware

Shaper choice. Klipper recommends MZV or EI for most printers. EI tolerates frequency changes better, which suits bed-slingers whose bed mass grows during a print and delta printers, but it smooths more ^[1]. Marlin’s built-in shaper is ZV ^[3]. OrcaSlicer notes that firmware defaults differ: MZV for Klipper and ZV for Marlin ^[12].

Slicer-driven calibration. OrcaSlicer’s input shaping test prints a ringing tower across a frequency range, 15–110 Hz by default, with damping usually started at 0.1–0.2. It asks for the highest acceleration and speed the printer can run without losing steps, and an opaque glossy filament makes the ripples easier to read ^[11]. The full walkthrough is on the input shaping calibration page.

Acceleration, smoothing and max_accel

Input shaping does not make acceleration free. Klipper explains that higher acceleration with a shaper adds smoothing, visible as a widening of the 0.15 mm gap in its test model, and recommends using the lower of two values: the acceleration where ringing is acceptable and the one where smoothing starts. In its example the gap grows from 3500 mm/s², so max_accel is set to 3000 ^[1]. SHAPER_CALIBRATE prints a suggested max_accel for each shaper, but it does not change the [printer] setting by itself ^[2].

Klipper also advises keeping square_corner_velocity at its default of 5 mm/s when using input shaping, because raising it adds smoothing ^[1]. Marlin’s jerk and junction deviation settings play the same cornering role; the cornering settings guide compares them.

If ringing measurements are unstable, with oscillation spacing that varies along one axis, Klipper says the printer may have several resonances on that axis and points to a separate procedure for that case ^[1].

Order of operations

1. Confirm the pattern follows corners, not layer height.
2. Tension and inspect belts, clean rods, tighten anything loose, and put the printer on a firm surface.
3. Measure the frequency per axis with a ringing tower or accelerometer.
4. Enable the shaper and choose a type.
5. Set max_accel from the ringing and smoothing results.
6. Re-check pressure advance; Marlin notes its frequency sweep runs with Linear Advance off and the K factor may need recalibrating ^[3].

Loose belts also produce layer shifts, so a printer showing both needs belt work before any tuning.