Ghosting / Ringing
Ripple pattern on surfaces near sharp features — an echo of corners, letters, or holes repeated as a decaying wave across flat walls.
What It Is
Ripple pattern on surfaces near sharp features — an echo of corners, letters, or holes repeated as a decaying wave across flat walls.
How It Forms
When the toolhead changes direction sharply (at a corner), the sudden deceleration and re-acceleration causes the mechanical system to vibrate. The toolhead overshoots the corner, bounces back, overshoots again — each bounce smaller than the last.
This vibration imprints on the deposited plastic. The nozzle is laying down material while oscillating, so the wall surface gets a wave pattern that decays with distance from the feature.
Every printer has a natural resonant frequency determined by its mass and rigidity. Input Shaper works by sending counter-pulses that cancel this frequency — destructive interference at the mechanical level.
Visual Signature
- Ripples radiating from corners on adjacent flat surfaces
- Echo of text/logos on smooth walls
- Vertical bands at regular spacing
- More pronounced at higher speeds
- Pattern spacing matches printer’s resonant period
Root Causes
| Cause | Calibration Variable | Direction |
|---|---|---|
| Input Shaper not tuned | Input Shaper | disabled/wrong |
| Belt tension too loose | Belt Tension | ↓ |
| Speed/accel too high | Max Accel/Velocity | ↑ |
| Heavy toolhead | — (hardware) | — |
| Loose frame/bearings | — (maintenance) | — |
How the Auto-Tuner Detects It
- Accelerometer (ADXL345): Measures actual vibration frequency during test moves. Already used by Klipper for input shaper calibration.
- Camera: Surface analysis detecting periodic patterns near features.
How the Auto-Tuner Fixes It
- Calibration: ADXL345 frequency sweep → find resonant peaks → select optimal shaper type and frequency
- Belt tension: Frequency analysis ensures belts are at correct tension before shaper tuning