Eliminating 3D Print Ghosting: How to Calibrate Klipper Input Shaping with an Accelerometer

Pushing modern CoreXY and bed-slinger 3D printers past 200 mm/s often introduces an annoying visual flaw: ghosting, or ringing. These faint, repeating ripples echo across flat outer walls immediately following sharp corners, embossed lettering, or holes. While many makers frantically tighten belts, grease linear rails, and stiffen frames, mechanical tuning alone rarely cures the problem.

The true culprit is physical resonance. Every printer frame, toolhead carriage, and belt system naturally vibrates at specific harmonic frequencies when directional momentum changes abruptly. In 2026, the gold-standard fix in Klipper firmware is Input Shaping—an open-source algorithmic filter that uses accelerometer telemetry to neutralize mechanical vibrations in real time.

How Input Shaping Neutralizes Resonance

Input shaping works not by slowing down your toolhead, but by mathematically timing motor acceleration steps to cancel out the frame’s natural spring-mass oscillation:

• Opposing Vibration Pulses: When the printhead makes an abrupt 90-degree turn, the shaper algorithm splits the motion command into tiny, phase-shifted sub-pulses. The second pulse generates a counter-vibration that destructively interferes with the first, leaving the nozzle completely steady.
• Targeted Frequency Damping: Rather than dampening all frequencies (which would soften sharp external corners), algorithms like MZV, EI, and 2HUMP_EI surgically target only your machine’s exact resonant frequencies.
• Faster Clean Accelerations: With resonance canceled in firmware, you can safely double your slicer acceleration values—often exceeding 10,000 mm/s² on rigid CoreXY machines—without sacrificing crisp surface finish.

Hardware Setup: Mounting an Accelerometer

Calibrating your shaper begins with temporary or permanent sensor rigging:

• Accelerometer Selection: Standard SPI-based ADXL345 breakout boards or modern plug-and-play USB accelerometers (such as KUSBA or BTT S2DW) offer direct digital readouts with minimal wiring hassle.
• Rigid Toolhead & Bed Mounting: Bolt the sensor firmly to your printhead carriage for X-axis measurement, and clamp it directly to the aluminum bed plate for Y-axis sweeps. Any flex in the mounting bracket will distort resonance data.

Running the Calibration Workflow

Executing the automated tuning routine in Klipper takes only four steps:

1. Connect the accelerometer and run ACCELEROMETER_QUERY in your Klipper console to confirm stable I2C/SPI communication.
2. Execute TEST_RESONANCES AXIS=X followed by TEST_RESONANCES AXIS=Y. The printer will hum as it vibrates through a 10 Hz to 130 Hz frequency sweep.
3. Generate frequency response charts using Klipper’s built-in Python scripts to identify peak amplitude spikes and recommended shaper models.
4. Save the calculated shaper frequency and filter model (e.g., shaper_type_x: mzv, shaper_freq_x: 54.2) into your printer.cfg.

Final Thoughts

Hardware rigidity matters, but physics has limits. By pairing an inexpensive accelerometer with Klipper’s resonance compensation, you unlock maximum print speeds while keeping every outer wall flawlessly smooth.