Troubleshooting - Command CNC motion stops

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patdonk
Posts: 3
Joined: Sun Aug 11, 2019 12:35 pm

Troubleshooting - Command CNC motion stops

Post by patdonk » Sun Aug 11, 2019 3:11 pm

hello,
I tried to post this earlier but it doesn't show up so forgive me if this is a duplicate. I am having a problem where all motion stops on my table but command cnc continues to run through the code as if it thinks it's is still cutting. I don't get any diagnostics and the only way I have found to get the motion to start again is closing and restarting the program, the position gets lost and I can't get started in the same place even if I find the correct M5 where I need to start over it's slightly off so the piece ends up being junk. I have noticed that this happens everytime during scribe operations and not as often during plasma cutting but still frequently. Things I've tried to troubleshoot are all connections, and cycling power to the hub. I've also tried to run some saved code from other files that worked fine in the past and still get the same problem. I have not made any programming
or settings changes and am running the same post revision 24 I've always used. thanks in advance for any help.

Rodw
Posts: 263
Joined: Sun Aug 21, 2016 1:49 am

Re: troubleshooting

Post by Rodw » Mon Aug 12, 2019 4:16 am

That sounds strange. I have never used CommandCNC but do know Linuxcnc well which is what CommandCNC is. I suspect it is a hardware or wiring fault or possibly even electrical noise in your system (low probability). If Linuxcnc is chugging through your file on screen, it should be sending motion commands. I would check all wiring connections are tight and reseat all connectors. If there is a fault on the motion control card, a watchdog should bite and halt motion. Re the scribe, the only thing I can think of is that the solenoids are drawing more power than the system can deliver or you have a fault there somewhere. Wierd.

weldguy
Posts: 300
Joined: Fri Apr 17, 2009 11:48 am

Re: Troubleshooting - Command CNC motion stops

Post by weldguy » Mon Aug 12, 2019 10:47 am

It does sound like an electrical noise issue. I had a relay in a control box one time for a scribe and when the relay coil energized it caused the controller to shut down. Moved the relay outside the box and problem solved. This won't completely fix your problem since it does it with the plasma also but check all your AC plugs and be sure the ground pins haven't been removed and that your AC outlets are wired properly with grounds.

patdonk
Posts: 3
Joined: Sun Aug 11, 2019 12:35 pm

Re: Troubleshooting - Command CNC motion stops

Post by patdonk » Mon Aug 12, 2019 4:58 pm

thank you for the replies so far I will look into those suggestions and report back.

Rodw
Posts: 263
Joined: Sun Aug 21, 2016 1:49 am

Re: Troubleshooting - Command CNC motion stops

Post by Rodw » Mon Aug 12, 2019 8:03 pm

Just reading another forum and one of the really experienced guys said
I was playing with a machine the other weekend where the stepper drive stopped working after a while. It turned out that that drive was set for maximum current. Turning it down to the second-from-max fixed the problem. Oddly there was no sign of the (tiny) stepper motors overheating,
Might be worth a look.

patdonk
Posts: 3
Joined: Sun Aug 11, 2019 12:35 pm

Re: Troubleshooting - Command CNC motion stops

Post by patdonk » Tue Aug 13, 2019 7:42 pm

thank you for another suggestion rodw. I checked some thing the others mentioned and it still continued. I talked to Matt from Starlab and he had me try powering the Aux. inputs to the bladerunner with a different circuit than everything else. I probably never would've guessed to try this but so far the problem has not come back and it was doing it constantly before. I appreciate the responses and I think all you guys were on the right track. I hope this information helps someone else someday.

tcaudle
Elite Contributing Member
Elite Contributing Member
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Re: Troubleshooting - Command CNC motion stops

Post by tcaudle » Wed Aug 14, 2019 7:34 pm

Solenoids and big relays are extremely noisy devices that kick back big spikes into the AC line. If the controller and AUX AC are in the same plug of branch circtuit it can get back into the main AC to the control box.

One thing the controller has is a safety "watchdog" (aka Charge Pump) it keeps the motors and outputs from coming on during a boot up sequence . Its signal comes from the Ethernet side. It is a constant frequency taht keeps the internal buffers enabled. If you lose the CP (light on the side of the box) it shuts off all of the motor signals but CommandCNC keeps pumping out the pulses. It will then cause the actual position to vary from the indicated position. Only way to re-sync is to have Homes (X and Y ) to establish a TABLE ZERO and do home moves using the Buttons The problem occurs when you no longer have a known table zero. Even if you move over and zero the work zero spot it will remember that offset as long as you can get back to the tabel zero points (HOMES) . It never forgets where home is or where work zero is in relation to home. As long as the material has not moved you can reestablish a cut very accurately.

When you do HOme the table do not rezero the XY there. It knows where you set the original work zeros and it assumes they are in the same place offset from the table home. Internally EVERYTHING is measure in absolute distance from Table (Machine) Zeros. Everything is in offsets from there. You can see the existing offsets by clicking the OFFSETS button in the upper right hand menu bar.

tcaudle
Elite Contributing Member
Elite Contributing Member
Posts: 1146
Joined: Tue Feb 28, 2012 6:47 pm

Re: Troubleshooting - Command CNC motion stops

Post by tcaudle » Wed Aug 14, 2019 7:41 pm

for external solenoids or bigger relays we suggest a device called a Snubber (AC Snubber) across the coil of each device . Kills that big back spike

https://www.ebay.com/itm/5-ITW-504M02QA ... Swiuxb32jV

It also prevents the contacts on the internal AUX relays from arcing over .

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