Frequent disconnects S03 XXL

It seems like I cannot even face the spoil board without encountering the GRBL disconnect error. I’m using a chinese spindle motor. Spindle and all metal parts of the router are grounded. Spindle cable is shielded. I have a mains isolation transformer and a USB isolator. I’m using the latest version of the controller. It seems like I have done a lot and it’s nowhere working.

Does the machine disconnect if you do an “air cut” with the spindle off?

Seems like you’ve done pretty much everything listed at: — are you sure there aren’t any ground loops? Which USB Isolator did you try? Have you looked into external causes? Say a heavy load on the line such as a compressor?

Have you considered using a Makita RT0701? It’s about as quiet as a spindle, has a decently low speed range and works quite well.

Are you using a dust boot? I had issues once where the MDF was causing a bunch of static build up on the vac hose and arc to the router causing disconnects that’s the only other thing I can think of.

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@WillAdams: Purchased a Makita to try. It could be crappy chinese electronics/inverter. Perhaps I could hook up an oscilloscope and poke around as well.
@lxkhn: I do, I have the SUCKIT dust boot.

Just tried a makita and it still does it. I tried a couple air cuts or almost air cuts and it was fine. As soon as I lowered the Z Zero to actually cut, it would die off. I’m wonder if it is the dust boot. Maybe I can tap some screws around it and give it something to arc onto rather than the spindle/router?

Try properly grounding the dust boot / hose — either use a conductive hose or run a connecting wire from the dust boot all the way to the ground at the vacuum (star topology).

Haven’t tried it myself, but it has been suggested by other forum members to run a ground to the router body itself. You can get a properly rated cord with a 3 prong plug and replace the stock Dewalt cord, use the ground from that. Again I haven’t tried it myself (I’m lucky and have never had EMI issues). Also make sure to route your power cord well away from any other wiring/electronics. If you have to cross stepper wires, cross them at 90 degrees, don’t route them in parallel.


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It seems like for those affected by the issue, we have to jump through hoops just to get it to behave correctly and it’s pretty frustrating. Who knows how much time, money, effort I’ll dump into trying to get this darn thing to work and that’s not even a guarantee. Rather than attacking everything external to the arduino/motion controller, any ideas to super shield it from all kinds of interference? I’m running the latest revision of the board with the two huge capacitors. Would changing the stepper wires out to a shielded cable have any effect?


Peter I think either I missed it or it was not asked. Where are you located? What voltage are you on? Who is your power provider? Have you used fault ground circuit tester in the socket you’re plugging the router into? How are you verifying you have earth ground in your circuit? You may need to widen your scope to resolve the issue.

Thank you


Yeah. there have been a couple of instances of a refrigerator being on the same circuit being the culprit, and on one occasion it was actually a failing transformer supplying power from the street.

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Hi Peter
I have same issues since 1st CM4 released, Carbide sent me an USB isolator and I never have to use it. What I did is search on the internet and continue search and found a vendor website who sell Chinese made water spindle. Everything are grounded, they are all grounded each device use different outlet which also on difference circuit. Still disconnect errors message and have to cancel the job from stated task. I saw an article with diagram showing how to wire the inverter to the spindle and how to ground and have a complete closed circuit. What I did not ground is:
The inverter is plugin the wall socket with ground.
The spindle shield cable has 4 wires ( one is ground/black color ) which connect to the inverter.
I run a separate wire o the ground port of the inverter, to the shapeoko controller board.
I never have any more problem since. I did have a video showing this, and i will post it on you tube and put he you tube link here so you can see

I have previously checked other outlets in the house with an outlet tester and it looked normal. I can’t find it so I ordered another one to test the outlet in which everything is plugged into. I’m assuming it should be normal as well.

In terms of grounding, there’s no ground loops and all the rails are grounded together. The Chinese spindle was grounded using a shielded cable. The Inverter is wired into a junction box and ground is properly connected.

I never had the issue with disconnects until I updated to CM4 or at least it seems that way but I added the SUCK IT at about the same time so the extra static may be the issue. Mine will disconnect almost every time I turn the router off which points me at probably a spike on the ground since the motor windings have to dump the field somewhere. I will be trying the 3 wire grounded power cord on my Dewalt to see if that takes helps then an anti-static hose for the dust boot.

Are you turning the router off using the switch on the router, or a remote switch?

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I have done it both ways. With the XXL it’s a reach to get back to the router at the end of a job so have it plugged into a power strip with a switch, I have tried just about every configuration possible with plugging the router, vac, and shapeoko into different outlets/circuits and nothing seems to help. I have been meaning to rewire the router to have a physical ground to the housing to see if that helps as it is really annoying when it resets.

As @dtilton71 stated id try a remote’s a cheap one to try if you already dont have one to test with.worse case return it.sure beats rewiring the router Imo.

I would put money on it being a grounding issue. I used a multimeter in continuity testing mode to check grounding loops between the spindle and other parts of my setup. In the end I found the monitor running my bCNC setup had a rubbish ground. I removed the grounding from the LCD as its just a low power system anyway and have not had an issue since. (approx 6 months). Possibly not the best solution safety wise, maybe more advisable to put an inline ground isolator.

But for general troubleshooting purposes I would try…
*Check grounding
- check for good earthing (earth your router/spindle if it is not)
- earth Shapeoko (I earthed X gantry to get static from around the spindle before getting to controller board)
- remove grounding loops
*Air cutting spindle off
*Air cutting spindle on
*A few different samples of gcode if possible from different generators
*Different motion control software (carbide motion, bcnc, universal gcode sender etc…)
*Try different computer hardware attached to the Shapeoko (laptops, PC, raspberry pi)
*Try running off battery and on wall power if you have a laptop
*Try different wall sockets for your shapeoko and spindle (ie Shapeoko on one socket and router on a long extension to another socket on other side of room)
*Could try USB isolation devices (SMAKN USB Isolator model: FBA_BC80927)
*Dust collection static discharge may need earthing

I went through all these step in some order and found success so hopefully this will help in some way.

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Been running for 30+ minutes straight using a .25 endmill to face the spoilboard. Perhaps the fly cutter generates too much static?

Also I have my vacuum on a remote switch and it’s awesome. Could totally do this for a router.


Two things I’ve found that might be useful.

The act of switching on an appliance i.e. a vac or the router can sometimes generate a small arc on your neutral line which will cause a disconnect. I found a good way to fix this was run all my high power items from a relay switch board - a bit like your solution there with the remote control.

I also found the router generating static was an issue - earth your router and frame and if you can move your control board to one of the side gantries this helps.

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For those talking about grounding the router by replacing the power cable, I did this a couple of years ago, and it helped me quite a bit. I put a write-up about it on the other Shapeoko forum. But, as user woodworkerbob added at the end of my write-up, you can also just add an external grounding wire without replacing the router’s power cable. That is a great way to at least test the solution, before going through the effort of replacing the power cable.

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