High Speed Printing with Input Shaping

Danielle A.

Breaking the Speed Barrier

For years, the practical speed ceiling for FDM printing was set by a mechanical phenomenon: resonance. When a printer's toolhead (or bed, on bedslingers) changes direction rapidly, it vibrates at characteristic frequencies determined by the machine's mechanical stiffness, mass, and damping. These vibrations leave visible artefacts on print surfaces, a characteristic ripple pattern called "ringing" or "ghosting" that degrades print quality proportionally with speed. The faster you print, the more ringing appears. This seemed like an inescapable physical limitation until input shaping algorithms changed everything.

Input shaping is a control technique borrowed from precision robotics and CNC machinery that modifies the acceleration profile of movement commands to actively cancel the printer's resonant vibrations. Rather than just speeding up from point A to point B, the firmware figures out a way to speed up that creates vibrations that cancel out the printer's natural vibrations, stopping the ringing before it starts. The result: prints at 300mm/s+ that look identical to prints at 60mm/s. Bambu Lab's commercial success has demonstrated this capability to millions; Klipper brings it to any printer.

Measuring Resonance with ADXL345

Implementing input shaping in Klipper requires measuring your printer's actual resonant frequencies, not guessing them, but measuring them precisely. An ADXL345 accelerometer (a tiny, cheap sensor chip) is mounted rigidly to the toolhead. Klipper then commands a frequency sweep, vibrating the axis through a range of frequencies, and the ADXL records the resulting accelerations. The data is analysed to produce power spectral density (PSD) graphs that clearly show the resonance frequencies and their intensities. Klipper then recommends the optimal shaper algorithm and frequency values.

Mount quality is critical: the accelerometer must be rigidly connected to the toolhead or bed, with zero flex in the mount. Any mount flex will produce corrupted data that leads to ineffective shaper values. Print a rigid mount bracket from PLA and use epoxy or short screws with no slop. Run the calibration twice and verify the results are consistent; measurement noise should produce similar shaper recommendations across runs. A rigid printer with well tensioned belts and tight pulley grub screws will produce clear, sharp resonance peaks which are easy to compensate for. A loose printer produces broad, messy spectra that even the best shaper can't fully correct.

Choosing and Applying a Shaper

Klipper offers several shaper algorithms: ZV, MZV, EI, 2HUMP_EI, and 3HUMP_EI. Each is progressively more effective at suppressing a range of resonance frequencies, but at the cost of progressively more smoothing of the acceleration profile (which reduces maximum effective print speed). The recommendation from the calibration run is usually the best starting point, but understanding the trade offs (covered in our resonance compensation deep dive) allows you to make informed choices. Apply the shaper values to printer.cfg under the [input_shaper] section. Run a print at 200mm/s and compare the surface quality to a pre shaper print, the improvement is typically dramatic and immediately visible.

Filament at High Speed

At high print speeds, filament quality becomes critical. Inconsistent filament diameter causes flow rate fluctuations that are amplified at high speed, a 0.05mm diameter variation that's invisible at 60mm/s becomes noticeable at 300mm/s. OzFDM filaments are manufactured to tight diameter tolerances specifically for this reason. Dry filament is equally important when there are moisture induced flow interruptions that are a minor annoyance at low speed can become print ruining defects at high speed. Combine input shaping with pressure advance tuning and quality, dry filament for the complete high speed printing experience.