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IndustryArena Forum > CNC Electronics > Gecko Drives > Motor overheating problem
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  1. #1
    Join Date
    Feb 2011
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    0

    Motor overheating problem

    My machine has been in mothballs for about a year while I was building my new workshop. I'm about to crank it back up, but I need some help, advice, whatever. I'm using Mach3 on a WinXP machine with a Keling package of Gecko 540, 387oz NEMA 23 motors with the included PSU running around 48 V. Using the math I found on here and the motor specs, I came up with the size of current limiting resistors, and asking a few questions out here, I feel I'm using the right ohm values. BUT....... for the 2 years or so I've had it running, I've always thought that my motors ran way way too hot. The last time I used the machine, I was cutting a pretty detailed relief of an eagle head, and finally, after about 3 or 4 hours of cutting, the X axis started moving erratically, ruining my carving. The X motor was way too hot to touch, Y not as much but still pretty hot.
    The limiting resistors may not even be my problem, so I'm needing help to cure the overheating problem before I start cutting again. Motor temp was well over 200 degrees, if I can trust my VOM and the temp probe.

  2. #2
    Hi,

    stepper motors can get pretty hot - too hot to touch is not unusual even at correct current. I have one rated for 260°F - it boils water instantly after being used for a while.

    I'd check if the current is really within limit - if so I would'nt worry about it.


    Christian
    My CAM Software and CNC Controller: www.estlcam.com

  3. #3
    Join Date
    Mar 2008
    Posts
    3655
    What size resistors are you using?

    Turn off power. Open the DB9 shell and measure ohms cup to cup to make sure that's what you actually HAVE in the resistor.

    CR.
    http://crevicereamer.com
    Too many PMs. Email me to my name plus At A O L dot com.

  4. #4
    Join Date
    Mar 2008
    Posts
    3655
    The 387 needs a 3.5K or so resistor. Make sure you HAVE 3.5K across pins 1 to 5, and not 3500 ohm. EDIT: This was supposed to be 350 ohm.

    I use these:
    MFR-25FBF-52-3K48 Yageo | 3.48KXBK-ND | DigiKey

    CR.
    http://crevicereamer.com
    Too many PMs. Email me to my name plus At A O L dot com.

  5. #5
    Join Date
    Feb 2011
    Posts
    0
    I built the system about 4 years ago, and my old senile brain seems to think I needed 3.2 K resistors. I know I bought 1% of whatever value I needed, and I measured the resistance to make sure they were close to what my math told me to put in. Keling evidently no longer sells the same motor I bought, so hopefully they can help me with the specs to refigure the actual size I needed. Still not sure why the x axis just went crazy the last time I used it. I've always had a minor problem with losing steps, but when it messed up, I zeroed my x axis manually, and it was at least 3 inches off.

  6. #6
    Join Date
    Oct 2012
    Posts
    28
    I read the Gecko G540 does not require current limiting resistors for motors 3.5A and above? That's the max it will work at?

    3.2K means 3.2 Kilo-ohms (thousand ohms) = 3200 ohms.

  7. #7
    Join Date
    Jul 2009
    Posts
    690
    The G540 will provide 3.5A if there's no resistor or the resistor is > 3.5K
    The problem with the above if that, even is the motors are rated at 3.5A, under that condition there's no current reduction (do not confuse with current limiting). Current reduction helps reduce heat by providing less current when the motors are idle, so you need a proper resistor. It's a good idea to go with a resistor slightly smaller than 3.5K to make sure current reduction is active, since they have a certain value tolerance and a 3.5K resistor can eventually have a slightly higher value.
    http://www.build.cl

  8. #8
    Join Date
    Mar 2008
    Posts
    3655
    Steppers can get very hot. Especially when wired parallel and connected to max voltage. A Good operating temp is 170 F, but they CAN get hotter. Measure your PSU to be sure it's not putting out MORE than 50 Volts. But the 387 is a 65V motor, so 50V should not cause a problem.

    Check the x motor resistor to make sure both leads have good contact. Make sure the resistor is not open circuit. That would be the same as no resistor and cause overheating.

    What kind of drive screws are you using?

    CR.
    http://crevicereamer.com
    Too many PMs. Email me to my name plus At A O L dot com.

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