Input shaping: how a printer suppresses vibration and ripples

What happens to a printer when direction changes

The print head is rigid, but the frame and belts vibrate slightly under sudden acceleration. This is ordinary resonance. The vibrations pass to the nozzle, and a ripple appears on the wall after a corner, known as ghosting or ringing.

The technique of input shaping originally came from the control of cranes and robots. The printer measures at what frequency its frame vibrates, and adjusts the motion commands so that the vibrations cancel.

How it is set up

With Klipper, an accelerometer measures the resonances of the axes, and the software picks the most suitable type of filter. See the Klipper documentation. Many commercial printers do this by themselves on first start-up or during calibration.

The setting is not free: the filter can round sharp corners slightly or lengthen print time a little, so a compromise is chosen.

The filter is set separately for the X and Y axes, because each has a different mass and a different resonance frequency. After the weight of the head changes, for example with a different nozzle or accessories, the measurement has to be repeated.

What you see on a part

• Straight walls without ripples behind holes, letters and corners.
• The ability to print faster without losing quality, which cuts time and so price.
• Fewer visible marks around fine lettering.

It does not help with everything. Ripples also come from a loose belt, a badly fixed plate or printing too fast, and those will remain.

For your order

Input shaping belongs to the printer, not to the file. From the model side you can help by rounding edges (fillet) and by avoiding thin smooth surfaces, where ripples are most visible. The print time that is in the price is taken from the real print preparation, not from an estimate.