Higher current than rated for short time



  • Hi all,
    I am constructing a T-lock for my tool charger right now and I want to drive it with an E3D slim stepper motor. It is working fine but the motor tends to skip steps since the torque is only about 13 Ncm. Now I am wondering if it is possible to increase the current of the stepper beyond the rated 1.4 A to reach higher torque. Since the motor is in idle mode for most of the time and only moves when locking or unlocking the tool I was hoping it could take it. Does anyone have experience with this and can estimate how high I can go. And is there any danger for the Duex board to which it is connected?

    Thanks ahead
    TC



  • I've gone a little past my tool lock stepper. The only thing to be careful: There is only ONE "idle" current factor for all steppers. So if you are thinking about upping lock motor current, and lowering standby %, be aware that you could cause your XYZ motors to not hold at that lowered %.

    Very low risk for the driver.

    And, last thought: I am using a planetary geared stepper, for the reasons you describe, on the lock only. It doesn't (much) matter how fast the lock/unlock occurs. More torque than heat (from current) is a good use for gears.



  • @Danal Thanks. Yes that is an important point. That is why I planned not to change the idle factor but to increase the motor current just before the motor moves and then to decrease it again. Is that possible?

    Of course a geared stepper would be better but space is a very critical parameter in my setup. That is why I wanted to try it with the slim stepper in the first place.

    Can you estimate how much I can increase the current for about one second? Double it? Is it just a question of heat development or are there other ways the stepper could damage itself?


  • administrators

    I recall reading on the E3D forum that the coupler motor current is increased to 600mA during coupling/uncoupling, and reduced to 400mA afterwards.



  • @TC said in Higher current than rated for short time:

    That is why I planned not to change the idle factor but to increase the motor current just before the motor moves and then to decrease it again. Is that possible?

    Yes, entirely possible. Duet configuration commands are fully dynamic.

    @TC said in Higher current than rated for short time:

    Can you estimate how much I can increase the current for about one second? Double it? Is it just a question of heat development or are there other ways the stepper could damage itself?

    AFAIK, heat only. Infrared it while doing a long sequence of tool changes. Look up for your individual motor, but generally they can get pretty hot with no damage.



  • @Danal thanks a lot


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