I’m one of the CNC Operators of our VR5050 CNC and am reaching out due to issues with our CNC machine. We are having an intermittent issue where the spindle refuses to start spinning (and sometimes slows down → stops mid-cut). We are pretty sure we aren’t overloading the spindle since it happens both during cuts and when it’s not cutting through material, just free spinning. It even occurs intermittently before the first cut of the day - when the motor is completely cool to the touch.
When this issue randomly happens, everything else on the CNC works besides the spindle. The cooling fan for the spindle turns on, but the spindle itself doesn’t. The ESTOP is not triggered either from what we can tell from the computer monitor. An adult mentor and our electrical lead have visually inspected as many wires as possible and see no breaks. We also felt no resistance on the spindle motor when powered off. We’ve isolated the issue so far to the control panel box.
Problem History:
This issue occurred once in February 2023. Unsure of how to fix it, we power-cycled the whole CNC and the spindle started spinning again.
Occurred a couple of times in August-September of 2023 but a power cycle always resolved the problem
January 20-21 2024: Occurred very frequently where a power cycle doesn’t seem to fix the spindle.
January 23 2024: We are suspecting a potential ground issue or loose connection? We found that if we tapped the back control panel when the spindle was having the issue it would start back up again.
If there’s teams that have had this similar issue and were able to fix it advice would be greatly appreciated. Otherwise if there are any Bay Area teams or you know of a CNC repair service or technician that can come in and take a look we would much appreciate that help. We can provide a video for context of the tapping and photos if needed.
I don’t know a ton about electricity/motors but it sounds like it could be a symptom of the carbon brushes in the motor going bad considering it’s decrease in performance, not always just working/not working. In a lot of power tools they can be replaced, but it depends on the exact spindle motor you have. If it’s some sort of palm router, it may be easier to find parts for it than some no-name brand spindle.
That right there, at least to me, screams a loose connection, cracked solder joint, failing/failed relay contact, or some other mechanical fault in the electronics. I’ve seen this a few times (at least?) in my 8 years as a controls and manufacturing engineer.
What can happen is a loose joint (or failing relay contact) provides poor (but initially sufficient) conductivity, but the marginal resistance causes the metal to heat up and distort, breaking the connection. Sometimes letting it cool down is enough to restore the connection. Other times, some mechanical persuasion (tapping, etc.) is enough to make things work again.
I doubt you have access, but my employer has used thermal imaging (FLIR cameras, etc.) on electrical cabinets to find suspect loose/faulty terminals. Back in 2020 I had the task of doing this our Mexican facility that just opened, and sure enough, I found a loose terminal (power wire through a relay) that was loose and getting VERY hot. Lit up the camera like the 4th of July! It’s more tedious, but one can also use an infrared thermometer to check anything suspect. Not that this does work best (requires?) the board to be “hot” (live), preferably in the faulted condition.
Heck, you could even use a plastic (non-conductive) stick to tap on components/connectors to isolate the bad spot (I’ve been known to tap on low-voltage relays to find sketchy contacts).
Be very careful of high voltage if you follow this advice…
I would check all your wiring connections to and from your VFD, spindle, and Velox control box. Use a multimeter to test the resistance of all of your wires end to end while trying to wiggle them.
We’ve checked the resistance of all the connections and they are all fine. There’s also no heat or warmth being produced. It’s a very inconsistent issue that’s very random when it happens.
This is likely a terrible idea, but perhaps swap out a relay to a different motor? I have no idea if this is possible on your CNC but it can help isolate the issue.
Buy a new spare spindle. Always good to have one around. Make sure the voltage, power, and collet size match what you have.
Make sure your machine is grounded. Make sure all cables in the control box are plugged in and do a tug test on the individual wires that interface with the VFD cables. Please do this with the machine totally unplugged!
When the spindle stops take a look at the display on the VFD for a fault code. You should also be able to reset it with the stop/reset button. We were having a similar issue with ours. Drilling holes would trip out the VFD with seemingly little load. I don’t remember the fault we were seeing, but I might have some notes. I think we needed up damaging the rectifier diodes in the VFD, but since the VFD has three phase input but only using single phase, I switched which terminals power is applied to it has been running fine since. There are two other configurations you could apply power, try both.
Generic safety note, Working on the VFD will require making connections on high voltage terminals. Be sure you or others have sufficient knowledge/experience to do so safely. This includes precautions for the stored potential in the VFD capacitors. Refer to the VFD documentation as necessary.
