[shepdog]

Hello, been lurking here for years with aspriations of CNCing my RF-3), but never got around to it. Been using a 3D printer for a while, and recently decided to use the pandemic lockdown time to learn the electronics side of CNC. So, I watched some youtube, did some reading, and decided to order a chinese package with 3 steppers, a USB board, power supply and three drivers. I figured for the $240 bucks it cost, I could at least see how Mach3 works, and if it would all run off my old laptop.

Well, it did! Got it all wired together, installed and moving! First big step...then got to the motor configuration and maaaay have set things a bit too fast for the bench test, and set the steps too high. Got that sorted though, and managed to run a circular pocket program. Here comes the question:

Running the program, the X motor decided to just stop working....probably thermal protection from what I can tell. If I unplug the system and replug it back in, the driver resets. Thought that maybe it was that one driver so I swapped X and Z...happened again to different driver, and then the Y driver as well...everytime, resets once powering down and on again.

I know these packages are cheap, and I see that the driver has a maximum 4 amps peak, while the motors are rated 4.0A. So I'm assuming the drivers are way underpowered.

QUESTION: can I set the drivers switches to a lower power setting to limit how much current goes through them, or will the motors just continue to try to draw 4 A and keep overheating the drivers? I know I'll have to replace the drivers if I ever want to build a proper router, but I was hoping I could at least keep running them on the bench for my own learning.

Thanks!

[Dean448]

I’ve never had a stepper driver overheat.
Drivers however can get hot over a long time and since it’s on the bench see if a fan helps.

Drives are controlled by a step and direction signal which are 5 volts. I would suspect something is going on with that signal on that axis. Could be a loose wire?
You can even bypass the computer with a frequency generator for steppers.


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[shepdog]

I’ve never had a stepper driver overheat.
Drivers however can get hot over a long time and since it’s on the bench see if a fan helps.

Drives are controlled by a step and direction signal which are 5 volts. I would suspect something is going on with that signal on that axis. Could be a loose wire?
You can even bypass the computer with a frequency generator for steppers.


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I swapped the X and Z axis wires at the board...I don't think it's the signal from the board, as the blue light which flashes with each step stays on solid...it's the green light indicating power to the driver which goes off...when I unplug the main power supply to the drivers, and plug it back in after only a few seconds, the driver resets and is operable, until it resets again after more use....or another drive resets. It only happens with the X and Y, presumably because the Z axis does not have that much sustained effort in the testing I've been doing, mainly a 3" diameter, 1 inch deep pocket....again, this is all being bench tested, no physical resistance on motors.

[Dean448]

Could you be exceeding the amp rating of the power supply? It fades and recovers when you disconnect the drives?
Btw I’ve been told to always remove power to the power supply and not just disconnect the DC voltage to the drives. Not sure which drives that applies too.


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[shepdog]

Not fading...just stops working. Everything came as a kit, so I can't imagine I'm exceeding the power output of the power supply...36V, 350W supply...the motors are rated 4.0 amps....

[Dean448]

Yea it does sound correct. However something isn’t right.
Motors are moving normally meaning they are wired correctly
Drive lights come on ok but shut down.
Nothing is loaded and just running some program.
No reason to consider high temperatures
Can you measure DC voltage when it shuts down?
I would try to find a way to prove the PS is not cutting out.


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[routalot]

What control software are you using and what settings have been applied to it?It could be something as simple as running a feedrate for milimmetres/minute in a program that is set to inches/minute and attempting to draw more current than the drivers can supply.

[machinehop5]

Not fading...just stops working. Everything came as a kit, so I can't imagine I'm exceeding the power output of the power supply...36V, 350W supply...the motors are rated 4.0 amps....

...the power supply maybe a little under powered... Is it getting hot? 4amps x 3 motors =12 amps@36VDC = 432 Watts
https://www.rapidtables.com/calc/ele...alculator.html

[dazp1976]

Normally with those kits you get 2* 36v supplies with 3 or more axis. One of them can just about manage with 2 axis of 4A motors.

[Dean448]

So I don’t believe his power supply is under rated. I’m running a 36v 400watt PS on a three stepper wood router. In this case the steppers are drawing the lowest current because they are on the bench. I’m working on the theory that this new PS is defective.


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[dazp1976]

So I don’t believe his power supply is under rated. I’m running a 36v 400watt PS on a three stepper wood router. In this case the steppers are drawing the lowest current because they are on the bench. I’m working on the theory that this new PS is defective.


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If the drivers are 50v max:
Scap the PS and buy a 48v of 500W minimum instead. (can achieve a higher velocity and stronger accel rate).
You need to factor in their efficiency too. These switched things prob waste 8 to 10% of their power.

I scrapped all my 36v based 'kit' ps's and drivers, kept the 425oz motors and bumped up to 60v. Gone from a mundane slug to a rocket. No motor heat problems, I just set the current down a level.

(Mill, PM25 sized. I have since updated to lower ind motors since then also)

[Toinvd]

For a test, disconnect the power to the Z axis and see if the other two perform normal. if so, it's most likely the power supply not strong enough.
Or for test, lower the motor power with the switches on the drivers.

[shepdog]

For a test, disconnect the power to the Z axis and see if the other two perform normal. if so, it's most likely the power supply not strong enough.
Or for test, lower the motor power with the switches on the drivers.

This was really what I was asking in my original post...I did try this and it seemed to work a bit longer, but tripped none the less. The test program I'm running is a circular pocket just using the wizard in mach 3. The Z only runs about 4 times during the test program, moving the "bit" 0.25 " at a time, then the X and Y do their spiral clearing...it during the clearing that X or Y shuts off....

[shepdog]

...the power supply maybe a little under powered... Is it getting hot? 4amps x 3 motors =12 amps@36VDC = 432 Watts
https://www.rapidtables.com/calc/ele...alculator.html

Hmm....okay, daylight is slowly creeping in...I just took a look at the PS and see it says 36V 10A on the side....so, yeah, it's too small to run all three at their "max" of 4A each...even at the reduced setting it's probably maxing out if all three are running at once...so if I set the dip switches to an even lower power setting, should I be able to continue to at least bench run the motors as I work on my Mach3 skills?

[Toinvd]

yes , you can give that a try. perhaps at a lower setting, the power supply will just do the job.
that's also why I said For a test, disconnect the power to the Z axis. I meant disconnect the power lines to the driver

[shepdog]

OK, so i tried again today, disconnecting the Z axis, running just X and Y. Set the max current on the drivers down to 2.8 amps. Both of them will eventually just stop, mid program. Unplugging the power supply and replugging it in again resets both instantly, but only get another shorter run time out of one or both. Do the stepper drivers have some function that would shut them down without completely frying them? Really not getting this...

[shepdog]

Here's what I bought, if it helps diagnose the issue...

[dazp1976]

OK, so i tried again today, disconnecting the Z axis, running just X and Y. Set the max current on the drivers down to 2.8 amps. Both of them will eventually just stop, mid program. Unplugging the power supply and replugging it in again resets both instantly, but only get another shorter run time out of one or both. Do the stepper drivers have some function that would shut them down without completely frying them? Really not getting this...

Hang on. Just spotted you said: 'stops after short period'.... reset.... 'runs another short period'.
Any chance that it stops on line #500 in Mach?.
If it does exactly that, it's an issue with your actual mach license.
Just a thought.

[shepdog]

Thanks, but that's not it, because Mach 3 keeps running, as does one of the motors. If I unplug and replug it back in, the motor drive that tripped resets and starts running as per the gcode...set the amp switch on the two down to 2.8 now and it's been running a 2" deep circular pocket for the past 10 minutes or so...if it completes, I'm going to add back the Z axis with the same lower amp setting on its driver and see if it runs completely....

[dazp1976]

Thanks, but that's not it, because Mach 3 keeps running, as does one of the motors. If I unplug and replug it back in, the motor drive that tripped resets and starts running as per the gcode...set the amp switch on the two down to 2.8 now and it's been running a 2" deep circular pocket for the past 10 minutes or so...if it completes, I'm going to add back the Z axis with the same lower amp setting on its driver and see if it runs completely....

Must be the psu then.
Bench testing uses F all in power. If you've gotta drop that low, they can't be getting enough juice.
A single 48v 600w for all 3 and be done with it.

Aliexpress perhaps, if you are patient.