2 days work down the drain!

[signmarketingman]

I just observed something like this happen recently.
The dust collector ground wire came lose. I saw it hanging loose and attempted to reattach it while the system was running. I nice manly spark fired across the gap. It instantly changed the numbers on the DRO and moved the cutter into a strange area just like your photo shows on your job.
My vote along with the other guys is static.

[ChrisInEstes]

I forgot to add something to my previous post. I grounded the whole system to the ground rod only & not the electrical ground because of a lightening strike hitting the power lines right outside my shop. The surge from that took out my phone system and my old CNC control box. A more recent near strike took out my 60" wide format HP printer. My insurance doesn't cover damage that occurs from power issues, so luckily I bought it used and didn't have much money in it.

My current dust collection system is run in PVC pipe, so I don't run it to my router. One of this Winter's projects is replacing all the PVC with metal. More often than not, a vacuum puck would be in the way of what I route, so I'd not even have it on there anyway.

It really does point to a static problem. Having that happen after so many years of clear sailing sure brings back bad memories!

Thanks for all the input!
Chris

[IslaWW]

Chris...
Here are a few things that you may or may not know:

Static can be generated from simple cutting and air movement from cooling fans on spindle/router. You do not need dust collection to generate static. I have seen non cutting movement of a gantry thru the air generate a charge that will show up on a scope.
Test: Do plastic particles stick to the machine? If they do, you are charging something. PERIOD

That following common used woodshop dust collection grounding practice, which is mainly intended to prevent explosion, is nowhere near what is required for CNC use.

When PC based control is used, having a machine that has an earth ground connected to a computer with an electrical ground, may in many cases create problems due to differences in ground voltage potential. Same with running multiple grounds. If a driven earth rod improved machine performance, it was not grounded properly to begin with.

[ChrisInEstes]

Chris...
Here are a few things that you may or may not know:

Static can be generated from simple cutting and air movement from cooling fans on spindle/router. You do not need dust collection to generate static. I have seen non cutting movement of a gantry thru the air generate a charge that will show up on a scope.
Test: Do plastic particles stick to the machine? If they do, you are charging something. PERIOD

That following common used woodshop dust collection grounding practice, which is mainly intended to prevent explosion, is nowhere near what is required for CNC use.

When PC based control is used, having a machine that has an earth ground connected to a computer with an electrical ground, may in many cases create problems due to differences in ground voltage potential. Same with running multiple grounds. If a driven earth rod improved machine performance, it was not grounded properly to begin with.

Thanks Gary, some of the info in your post I knew, some I didn't think of.

I know that static can develop with air moving over a surface. I've seen grounding straps coming off the trailing edges of some airplanes even. I don't get a lot of plastic chips sticking to the machine when I (rarely) route it. HDU tends to stick a little more, but I'm not sure if that's static or just what HDU does.

I didn't even think of the computer being grounded to the electrical system, and the router being grounded through the rod. I don't have the computer chassis directly grounded to the grounding rod, but I guess I don't know if the 2 grounds are connected to each other through the USB cable connecting the computer to the controller. What would you suggest I do about that? Connect the 2 grounds? I'm afraid of grounding the CNC system to the electrical system ground due to the power surges that can and have occurred in the past.

I appreciate all the help!
Chris

[glenninvb]

Chris,
Sorry to hear of your messed up job, hope you get squared away. I think Gary knows his stuff.

Thanks for reminding me though, need to buy a UPS for my machine computer (all laptops nowadays except that antique) . Living on the coast, when the wind blows, especially during a northeaster the power cuts just enough to kill computer during job, servo drives aren't affected ( I guess big capacitors in power supplies?) That's why I jot down work cord's. at start.

[glenninvb]

Chris,
I'm somewhat familiar with floating grounds, reverse polarity, and other bad (dangerous) conditions in AC marine wiring. Your independent ground rod could actually create a safety hazard if a line to ground fault should occur (you could be the path). Like Gary said, equipment should be grounded to supply mains only.

I gave some bad, or incomplete advice a while back on here when suggesting someone using a nearby water pipe for a static dissipation test, I only meant to ground the electrically isolated vacuum hose as a test but didn't elaborate. An electrically isolated flex duct grounded by whatever means should not create a safety hazard? Mine simply grounds back to the blower housing and the hose is non-metallic and not earthed to the router.

Is your controller, and VFD physically attached to the machine chassis? Have you've disconnected mains grounds and rely only on the driven rod? Dry soil under slab could create a high impedance situation and a safety hazard.

........"These are my opinions only and not recommendations".......... I would love to hear Gary's thoughts on a proper mains ground scenario and if an independent but isolated static dissipation point is acceptable?... Opto-isolated computer to B/O boards and what static could do there?

If anyone feels any of my comments are incorrect, please step in !!!!!!!

I remove my 4 prong twist lock plug from receptacle when not using machine, and usb cable, lot of lighting around here as well.

[IslaWW]

Chris...
I can think of no reason that your system would not perform better and most assuredly safer, if you have the machine ground connected to the system as per the NEC and safety regs. If you have bad power removing the ground may put you and your components more at risk. You may want to investigate with your power company or an electrician the benefits of a line power conditioner. They will cure a good number of ailments.

IF we assume for a minute that you do not have a static problem, but one that is from some other electrical noise, there are line filters, line reactors for single and 3 phase sides of a VFD that are not overly expensive, but you will usually need a scope to determine the cause. Sometimes its another piece of equipment, maybe not in the same building. Aging VFD's can also start putting out dirty power.

Having the CNC machine on a cord that can be removed when storms approach is not a bad idea. Depending on the age and country of origin, your machine could use a tuneup to current standards. The additions of tens of thousands of computer controlled machines and network connected medical equipment has actually caused the NEC to be modified in the last few years. As has the internal requirements of CNC control.

Glenn...
There should be no lower ground potential point in the system than its ground buss. This will, in accordance with applicable codes, combine in some combination, the power company ground, driven ground rod(s) and water pipe connections. And if I understand the NEC correctly, all will be connected to the ground buss and all system connections to ground must be taken from there.

The industry standard is to ground the dust collection (usually metallic) piping back to the collector housing and ensure that it is properly grounded. This provides a path to drain static AWAY from the CNC machine and allows static induced spikes to dissipate by resistance, and the multipoint system at the buss. Remember we are looking to drain small, maybe even insignificant static discharge so that it does not impact our sensitive I/O and comm systems.

I recommend and will only use I/O boards that both buffer and opto isolate input, output and step and direction. Use of dual power supplies on either side of the optos decreases the chance of noise "jumping by" the opto chips. Keeping the low voltage wiring isolated from the chassis ground is important too. None of these options are cheap or free, but neither is down time.

[glenninvb]

Gary,
Thanks, for the info and hope Chris gets fixed up
Not to jack his thread but here's a photo of my controller cabinet with servo drives, line emf/rf filters, proper breakers and a single point ground buss
It may not be to industry standards but pretty sure NEC compliant. In the event of a line to ground fault I should survive
But do need to get a UPS for computer ASP

[scottp55]

Got my little machine on a 20A GFI breaker I WAS using as a wet grinding station. Was just wondering if that's OK or swap to a regular breaker? Haven't had any issues for the year I've been using it-just wondering.
Glenn, Not sure about your machine, but UPS for both computer/monitor and the Desktop was one of the better things we've done. Thunderstorm? Unplug UPS immediately/Pause cut/ turn spindle power off/ and then simply plug UPS back in after storm passes/resume cut. Longest storm was 1 hour 40 minutes---No Problems. Country Power here, and seemed to help with comm issues too.

[garylmast]

My CNC runs off of 220 Volt and because I couldn't find a UPS without paying a fortune, I install a Whole Home Surge Protection Unit at the end of my panel box that controls my shop. I got it at Home Depot.

[Good Ole' Mr.Wilson]

Great info!

I knew nothing about static issues causing the controller to freak out.

I am here in Colorado, with altitude & low humidity, and have a cnc shark. Nothing near the larger machines you folks mention.

It runs off of house current. I have been saving $$ for a dust collection system and am now apprehensive as to how to go about doing this without creating the same sort of problems.

Now I'll scour the forum for dust collection info before spending any cash on something that will become a headache.

[kyeakel]

Must be the sign has to be in this format? Why could you not cut the section out, make a new board with the lettering and glue it back in place? Or mill off the letters, and make raised letters that could be glued in place? Mill it flat to the letter depth, make an equal depth insert that has the letters cut out and glue it in?

Kipp

[ChrisInEstes]

Great info!

I knew nothing about static issues causing the controller to freak out.

I am here in Colorado, with altitude & low humidity, and have a cnc shark. Nothing near the larger machines you folks mention.

It runs off of house current. I have been saving $$ for a dust collection system and am now apprehensive as to how to go about doing this without creating the same sort of problems.

Now I'll scour the forum for dust collection info before spending any cash on something that will become a headache.

Where in CO are you? I'm in Estes Park, but that could still be 8-9 hours away from you!

Chris

[ChrisInEstes]

Must be the sign has to be in this format? Why could you not cut the section out, make a new board with the lettering and glue it back in place? Or mill off the letters, and make raised letters that could be glued in place? Mill it flat to the letter depth, make an equal depth insert that has the letters cut out and glue it in?

Kipp

This particular sign couldn't be quickly and nicely patched... Just because of how it was made and the clear finish coats & paint coats.

My customer OK'd me milling that side off and re-routing it. That resulted in a thinner sign than we both wanted, but I made the deadline and the sign looked fine.

Chris

[ChrisInEstes]

For an update, I haven't done much to mitigate my (likely) static issue.

What I have done is disallowed any other people in the room, and I don't run any other machinery while the router is running. since I've done that, I haven't had an issue.

I know I need to find and fix the actual problem, but do to my broken foot I just haven't been able to get to it yet. I have a HDU sign job coming up that will take around 8 hours of routing on each side of a 2-sided sign, so I'm nervous about that. I'm going to run a humidifier in the CNC room to get the humidity up.

I'm glad this thread popped up again, I've been meaning to locate it and read through it again so I can work on the "right" fix for my system. One thing that'll be fixed yet this Winter is my dust collection system. It was originally put up in a hurry using PVC sewer pipe we had on hand. I quickly learned that PVC ducts, static, and CNC machines do not mix well, so for 19+ years, I haven't had the dust collector system connected to the router. So finally the plastic ducts will be replaced with metal ducting, and will be fully & properly grounded.

Thanks!
Chris