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Determining Motor Currents

⚠️ The below guidance is for axis motors only.

Extruder motors/pancake steppers are a bit different, as there is more variance between models.

  • Check with the community first.

    • If you are using BoM motors, check the stock configs.

    • Check in Discord to see what others are running.

  • You should start off with a more conservative run_current.

    • You may be able to attain additional motor performance by increasing currents, but come back to that later. Get your printer working reliably first.

  • Some motors vary.

    • I have found my LDO 0.9° steppers to be able to achieve notably higher max accels/speeds with higher currents.

    • My OMC 1.8° motors, on the other hand, performed very well even at moderate currents.

  • We are derating the motors/drivers for margin of safety. Rated currents are the absolute maximum in ideal conditions. In reality, things like chamber and driver temperature come into play. Margin of safety is also standard practice.

  • TMC2209 drivers are rated to 2a RMS, but I would not exceed 1.4a RMS.

Determining Initial run_current:

Start with around 40-50% of rated current.

  • For example, with a 2a motor, start around 0.8-1a.

Then you can 📄test your maximum speeds/accels and make sure your motors are performing well. In most cases, the motors can handle speeds/accels much faster than what you would realistically be printing at, even at moderate currents.

  • If you are having issues reaching reasonable speeds/accels, you may have a mechanical problem. See 📄here.

Determining Maximum run_current:

⚠️ In most cases, your motors will reach maximum or near-maximum performance before this point. Don't just slap them straight to max current.

  • Often that just results in extra heat (and potential driver overheating problems) for little actual gain past a certain breakpoint.

  • Most 1.8° motors already have way more performance than you realistically need. 0.9° motors are more sensitive, however.

  • The ideal current is usually somewhere in the middle. Experiment with different motor currents and 📄test how they affect your maximum speeds/accels.

A good rule of thumb is to not exceed 70% of the rated current as absolute max.

For example, a 2a motor would be about 1.4a max.

  • Keep in mind that currents approaching maximum may need greater stepper driver cooling.

  • If you are pushing higher currents, you may also want to consider measuring the temperature of your motors. Ensure that they do not exceed 80C.

    • Measure the temps when actually printing in a heat soaked chamber.
      • Some multimeters come with a k-type thermocouple. You can kapton tape it to the motor housing.
    • You cannot accurately gauge this by feel. Even lower temperatures will feel "too hot".
    • The motors themselves can generally handle much more. This temp limit comes from the printed parts rather than the motors themselves.

Determining hold_current

Recently, Klipper docs have started to 📄recommend against using a separate hold_current. You can achieve this by commenting out hold_current, or by setting it to the same value as your run_current.

If you run a different hold_current, a good rule of thumb is about 70% of your run_current.

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