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DISCLAIMER: New to electrical engineering topics. I'm a 3d-printing hobbyist. I don't know all the Jargon being used but trying my best to keep up.

PROBLEM

Recently bought a Nema 17 stepper pancake motor to replace the Ender 3 extrusion stepper. It's only used for direct extrusion with a BMG 3/1 gear ratio, which leads me to believe it doesn't need a lot of juice to have it work optimally.

*Got this from TriangleLab:*

https://www.aliexpress.com/item/32768043304.html?spm=a2g0s.9042311.0.0.27424c4d4HQcug

This thin stepper is running very hot. Via pronterface and/or octoprint, I adjusted the "current" from the default ender 3 E850 to E50, using command M906 and saving with M500.

It is still running hot and TriangleLab hasn't been very forthcoming.

NOTE: i'm not sure what "current" is being referred to, amps or voltage. I just followed this youtuber's advice for the adjustment...

Used this guy's method: https://youtu.be/GHUr1a3nXDU

Question

How do I know if the stepper is running TOO hot? (not sure what the consequences of a hot stepper might be, other than the thing burning out and becoming a fire hazard.)

Is there a calculation that is better than just eyeballing the situation and doing random tweaks?

Any info would be much appreciated. Thanks in advance.

**Triangle Lab's Stepper specifications**

NEMA 17

 - 1.8° Step Angle
 - 200 Steps Per Revolution
 - 1.0 Amp
 - per phase 5.1 Ω 5.9mH
 - 21 N/cm Holding Torque
 - 23mm Body
 - 20mm Output Shaft(5mm diameter)(17mm D-Shaped)

......

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2 Answers 2

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Current is amps. The set of specifications you gave states

1.0 Amp

so as long as your current is <= 1.0 Amp then it doesn't really matter how hot it's getting because the motor is rated for that current.

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  • $\begingroup$ Thank you. I came across this and will check later to adjust the potentiometer screw on the motherboard instead of meddling through the command prompt in Octo. Ref: youtube.com/watch?v=hC4J29rxPlQ $\endgroup$
    – Pubwie
    Commented Oct 28, 2020 at 1:06
  • $\begingroup$ * Assuming there are no external heat sources further warming the motor. $\endgroup$
    – Ben ♦
    Commented Nov 5, 2020 at 16:40
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Ender 3's stock mainboard does not allow you to set driver currents in firmware, as it requires a TMC driver in UART mode and creality 1.x and 4.2.x mainboards run the stepper drivers in standalone mode. There's a little screw pot by each driver for setting the reference voltage.

This might be helpful https://teachingtechyt.github.io/calibration.html#steppers

Note whilst TMC drivers use rms current, supplied formula VREF = (RMS current * 2.5) / 1.77 simplifies to VREF= RMS Current * 1.41 so VREF ~= peak current for your convenience.

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  • $\begingroup$ Thank you. I did manage to set the current. Since then, I've replaced the board with a MKS Robin E3 with replaceable stepper drivers. It seems, for this board, driver current can be set either via the printer's marlin menu under advanced configuration, or the screw which you have pointed out. $\endgroup$
    – Pubwie
    Commented Apr 15, 2021 at 3:46
  • $\begingroup$ I think the pots on the drivers are used when the drivers are in standalone and when used in UART, as your board seems to do, they're totally softwere controllable. $\endgroup$
    – strayr
    Commented May 3, 2021 at 16:15

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