We have a power supply with 24V and 48V outputs for our CNC machine. The power supply completely shuts off during cycle. It seems to happen later in the day, and always in the same location during the cycle.
Lambda
Part Number H10704
Hello,
Is the CNC machine doing this same cycle throughout the day and only shutting down later in the day?
Hi Rob,
Yes, it happens later in the day, and during the same Z axis move at the same place. I can slow the machine down and it improves. It mostly happens when the power supply gets a little warm (measured at 110 degrees F)
Do you have a model and or part number for the supplies you are having issue with?
That part number appears to map to a cataloged specification for an older configurable supply; essentially a “custom” product that was made orderable, but without benefit of actual documentation being attached. Any reference one has available to a series designation or such that might help track down documentation might be useful.
That said, it would seem likely that there’s some sort of protection mechanism activating. Since the issue is so kind as to occur at a predictable point, one can note what the machine’s doing at that point for clues. If it happens as a bunch of mass is being lifted or spun up, fair chance that it’s something overcurrent-related. If it happens as a moving mass is being brought to a stop, it might be because of braking action causing an over-voltage condition. Slowing down moves would be expected to improve things in either case.
That the issue seems temperature-related is informative; perhaps the supply’s getting a bit furry inside from inhaling shop schmoo and needs a cleaning. If it’s old, there may be some 'lytic caps that are drying out and making a near-problem into an actual problem.
It occurs as a mass is coming to a stop. Funny thing is that I have several identical machines that have no problems. But this one does…. The lytic caps drying out is an interesting idea. How would I check that?
It looks like this page offers some explanatory information on the unit in question.
If that date code reads March of 2024 like it seems to, then dried out caps seem unlikely; that’s usually something that only happens after a rather long period of use/abuse.
I’ve not yet found documentation specifying behavior of the over-voltage protection, but a new-ish, clean-looking supply that hiccups when a mass is coming to a stop suggests to me that it may not be the power supply that’s at issue here, but potentially something related to the driven load.
Most power supplies aren’t particularly tolerant of having power driven back into their outputs, but servo drive systems such as you’ve likely got there are known for doing exactly that when braking a moving load. Perhaps there’s some failure or defect in a protection mechanism somewhere that’s causing problems with this specific unit… Hard to tell, but if there’s a sudden, substantial increase in output voltage immediately prior to shutdown it’d suggest that the issue is something of this nature. One would probably need something rather faster than a multimeter to observe this however.
I would suggest using either canned air or an air compressor with a moisture filter on the output to see if there is any dust type build up that may be an issue. And see if the supply runs better.
If that is not the case then you can visually inspect the capacitors on the internal boards.
If they look bulged or seem like they are leaking/ have leaked then those caps would need to be replaced.
I replaced the Beckhoff EL9570 Buffer Capacitor Terminal that is in-line with the Servo Drives, and also added the 10 ohm Brake Resister thinking that would help. Still the same problem.