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Author Topic: sudden onset of Stepper stalling  (Read 2508 times)

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sudden onset of Stepper stalling
« on: March 08, 2017, 08:39:56 PM »
I've got a Hoss mini mill clone that has been working great and almost daily for 18 months. Now it is suddenly stalling the Z-axis on a regular basis either while executing a program or just jogging. No pattern for when it happens. I verified that it is not a physical resistance issue on the machine. Never had problems in the past with stalling either, but it's not going away on it's own.

Is it possible I have either a dying breakout board or driver??? Or, is it possibly a windows stability issue? I've attached my XML file as I know you guys love looking at them!

I use the following:
KL-4030 driver
CNC4PC C-35 breakout board (parallel port)
Window 7 computer (only runs mach3, does not even connect to internet)
NEMA23 382oz/in 3.0A Stepper Motor

I had already considered moving to a motion controller as I'd read they offered more stability. Either the
UC400ETH Ethernet CNC Motion Controller
or the
UC100 USB to Parallel CNC Motion Controller

Any ideas on what I should do here?
thanks in advance.

Offline Tweakie.CNC

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Re: sudden onset of Stepper stalling
« Reply #1 on: March 09, 2017, 02:11:54 AM »
It's only a guess but check the case temperature of your Z axis stepper motor when this problem happens.
Just as a guide it should run at around 60 deg. C   If it is lower than this then you could try increasing your drive current by one setting.

Re: sudden onset of Stepper stalling
« Reply #2 on: March 09, 2017, 08:31:40 AM »
That's really interesting. So you're saying that the temperature could in fact be too low. I'll start checking it and see if there's a correlation.

I did order a UC100 motion controller to eliminate (or at least reduce) the chance that it's a windows computer problem. the computer has never changed but certainly windows always degrades in stability with time.

thanks for the idea there.
Re: sudden onset of Stepper stalling
« Reply #3 on: March 11, 2017, 03:38:17 PM »
I had a problem very similar except with the " y" axis...turned out the coupler between the stepper motor and the lead screw was loose.
Back and forth movement of the motor eventually caused it to loosen...I took the set screw out, put on some locktite, and really tightened it down...no more problems.

Hope that helps

Offline rcaffin

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Re: sudden onset of Stepper stalling
« Reply #4 on: March 12, 2017, 05:45:23 AM »
If the DRO behaves itself properly, you may have a hardware problem - like a loose coupling.

If the stepper motor is 'cold', then you may not be driving it hard enough. But this is unlikely if it has been running for 18 months, unless the power supply is sagging badly. Or the driver could be dying.

Re: sudden onset of Stepper stalling
« Reply #5 on: March 13, 2017, 06:27:08 AM »
while an external motion controller like the UC100 is a good idea it seems to me you should try to solve this issue without
introducing a whole new bunch of variables, like how you've set up your new controller.

If it is something like a sagging power supply or a weak driver circuit it will come back to haunt you irrespective of what controller
you use.

Do you use the same drivers for all axes? You could for instance swap the X and Z axis drivers over and if the intermittent stall now
occurs in the X axis rather than Z then the driver is bad or going that way. If the fault sticks with the Z axis then I would be looking
at the supply. Does the Z stall when going upwards? It may be the weight of the spindle and carrier is just enuf to cause the motor
to stall. If you increase the current drive and the fault goes away then it suggests that the motor is operating at close to its max torque
at that speed. If your drivers can handle more voltage and you can increase your supply voltage it will help maintain motor torque at
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Re: sudden onset of Stepper stalling
« Reply #6 on: March 13, 2017, 08:50:00 AM »
I think that it may be a failing driver. I pulled a known good driver out of my lathe and replaced the Z axis on the mill and the problem went away. So it appears I have a failing driver. I didn't realize that these drivers could sort of work. I thought a driver would either work or be dead but it seems to be 'failing'. For $30 it lasted quite a while and is a cheap fix.

After the driver swap I did install the UC-100 motion controller. I didn't notice any ground breaking performance increases but I would say the overall operation of the machine is 'smoother'. I'd been wanting to add one for a bit anyway to reduce potential windows issues.

I'll let it go for a week or two and will post back if the problem comes back. But certainly, if you've checked all of the connections, made sure it isn't a Windows problem, look at the driver itself. The running temperature is an interesting one. None of my drivers have reached 60 deg Celcius when running my programs. I just don't have enough sustained axis movement to heat them up. The KL-4030 are already at 'full current' and set to 3.0 amp. and the motors are rated at 3.0 amp also. not much I can do there. and everything did work fine for 18 months. to answer someone's question, yes, I use (3) KL-4030 drivers on the machine all running from a single 36Volt/9.7amp power supply.

Incidentally, I did move the 'bad' driver to the lathe, and it works fine. On these mills the Z axis clearly works the hardest so perhaps that is a contributing factor and maybe my KL-4030 and motor combo is a bit under-powered for the job. so it may be that I have been running it at it's limits for too long. with a lessened load on the lathe no issues. I'm replacing it anyway as it just isn't an expensive part and I enjoy making parts far more that working on the machines, lol.

thanks and I'll post back if it turns out the driver was not the culprit!