RRF Input Shaping

Some notes on using the InputShaping feature in RepRapFirmware

As of the date of writing, RepRapFirmware requires a LIS3DSH accelerometer to automate input shaping calibration. You can find the latest Input Shaping plugin at https://github.com/Duet3D/DSF-Plugins/releases. Disable Mesh bed calibration (G29 S2) before running tests.

General notes

1. on belt driven axes, multiple peaks on one axis indicate something is loose and is adding additional vibrations. Trying to find those and fixing them is a valuable venture anyways.
2. on kinematics combining drives such CoreXY it is desirable that the measured curves match, since it indicates similar tension. Do not confuse this with finding the right tension though. That is dependent on belt lengths and your motion system.
3. On Cartesian systems, individual axes may have different curves.
4. On RepRapFirmware -- other than klipper -- you can only set one input shaping algorithm, frequency, and damping setting. In practice, the damping factor is enough to cover the usual span of different frequencies on different axes.
5. The InputShaping plugin visualizes the measured vibration per axis, but also a recommended frequency, and you can tell it to show the effect on the frequency graph by a given algorithm and damping factor. Ideally, the damping factor is as low as possible to reduce the effect of input shaping on speeds/accelerations that aren't inducing ringing.

Interpreting the results

1. Each axis should have only one high peak (usually between 30 and 80 Hz). Multiple peaks indicate that something else affects the measurement. Ensure all wiring is secured with strain relief and neither the wiring loom to the print head and/or accelerometer, nor PTFE guide tubes or filament, causes drag and deflection. Find loose bolts and fasten them.
2. In the InputShaping plugin view, check the checkbox titled "Estimate shaper effect" to see how a given algorithm and configuration affects the measured curves
3. Adjust the damping factor so it closely envelopes the measured peak(s) to avoid excessive smoothing and/or slow downs
4. You may need to retune Pressure Advance after tuning input shaping since there is some interaction between input shaping and PA.