We have a 2016 PCNC770 Series 3 running Path Pilot V2.9.1 that has had intermittent spindle no-start issues.
We noticed it first when students were running an established and long used G-Code for a project. On occasion, the spindle would not start, and the end-mill would plunge and break. Path pilot would say the spindle RPM was at it’s desired set point. Students would swap to a new Endmill, and not run into the same issue.
More recently, the spindle would not start from the Main screen using the FWD function. Path pilot would read out the RPM as if it had reached its set point.
I opened the cover, jogged the motor a bit by hand, and the spindle then started.
Is it possible our motor is getting stuck between poles?
My thinking is that, after the endmill would break, students will perform a tool change and likely jog the spindle and motor a bit in the process.
I went through the troubleshooting method outlined in the “My Spindle Wont Spin” document. VFD has power and no error codes, 24V signals are all good. The resistances between UV, UW, VW are all ~6 Ohms, which is slightly higher than spec, but tests similar to another 770 we have that is working fine.
If anyone has any advice, would love to hear it, thanks!
I second opening a support ticket. No reason to suffer and keep breaking carbide.
Makes no sense to me how the output from the VFD to the control board is indicating the spindle is turning when it is not (unless this is open loop and it is assumed when the VFD is commanded, it has achieved the command). I would have a meter on those wires during the error condition.
I’ve opened a ticket, thanks fellas. The system is open loop on the older 770’s, so it makes sense as to why it would be displaying a spindle speed without any feedback loop.
Weird. It acting like it is a brushed motor (it isn’t) that needs service…
Assuming the spindle is okay (no bearing failure, not hard to turn):
Assume that the diagnostic procedure above has you check wiring thoroughly to each phase to make sure it is actually getting to the motor when commanded and no wires are loose / voltage is instant and at spec when commanded
VFD starting to fail (you could swap VFDs if you have the same machine and there’s no difference in programming/etc. and see if the other machine does the same thing)
Just to follow up, I opened a ticket, probed some things with Norman from support, and received a suggestion to replace the K2 main board relay. The Potter and Brumfield relays on the board are no longer made, but this G5LE-1-E36 DC12 was an equivalent part:
Tormach also sells the full replacement boards here.
To give more detail on the probing we discussed via email:
Probed 24V across J1-5 and J1-6 while the VFD was in “rd 0.0” state.
Probed 0V across J1-3 and J1-9 while the VFD was in “rd 0.0” state.
Probed 24V across J1-3 and J1-0 while the VFD was in “Fr” state.
The system seems to be working again, although it’s an intermittent issue, so I’ll check back after some students have run it through it’s paces to confirm.
Today in the middle of running a program, the mill began slowing down and then surging its spindle speeds. At one point it stopped completely and restarted.
I’ll re-open the ticket and report back with what else we try.
Had this problem a a few times a couple years ago on an 1100. Did a reboot to correct. In my case it wasn’t starting in manual mode. Not sure what caused it .
