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Calibration: Encoder

Only applies if your MMU has an encoder fitted - standard on ERCF, and available as an option on several other designs (see Feature: Encoder for what the encoder does and how to wire one up; this page is just the calibration command itself).

MMU_CALIBRATE_ENCODER measures encoder resolution - how many millimetres of filament movement correspond to one encoder pulse. It needs the current gate's gear rotation distance already calibrated (see Calibration: Gear) - the encoder measurement is only as good as the gear move it's measuring against.

Running it

Make sure filament is loaded at least as far as the encoder, then:

MMU_CALIBRATE_ENCODER

Calibrating over 400.0mm using 3 repeats:
Load direction: mean=368.67 stdev=0.58 min=368 max=369
Unload direction: mean=368.33 stdev=0.47 min=368 max=369
Before calibration measured length: 394.47mm
Calculated resolution of the encoder: 1.085049 (currently: 1.094543)
Encoder calibration has been saved

It moves filament forward and back a few times (REPEATS=, default 3) over a commanded distance (LENGTH=, default 400mm), counts encoder pulses each way, and derives the resolution from the discrepancy against the already-calibrated gear move. SAVE=0 reports the result without persisting it - useful for a quick check.

MMU_CALIBRATE_ENCODER LENGTH=200 REPEATS=5
MMU_CALIBRATE_ENCODER MINSPEED=100 MAXSPEED=300

A shorter/longer test move can help on MMUs where the default doesn't fit the available travel; MINSPEED=/MAXSPEED= spread the repeats across a speed range instead of one fixed speed, which helps catch a resolution that varies with speed.

If this step worked, MMU_UNLOAD should cleanly clear any residual filament left from testing.

Is this mandatory?

skip_cal_encoder in mmu_parameters.cfg controls whether Happy Hare insists on this: it defaults to off (calibration effectively expected) only on ERCF - every other encoder-equipped design, including KMS and QuattroBox which both ship with an encoder, defaults to skippable, quietly using the installed default resolution until you calibrate. Either way, skipping it doesn't stop the MMU running; on ERCF it just means Happy Hare nags at boot until you do. See Calibration for how this setting sits alongside the others.

See also