Interesting question. When they wear down do you think they may be taking a bumpy ride causing EMI?
I don’t have a problem but if I did I might put an inductive pickup on an oscilloscope probe and troll for a noise source. Maybe make my dust boot into a Faraday cage and put grounding straps at suspected emitters.
Is it EMI or RFI? Sounds like an interesting challenge.
These are interesting and involved ideas.
Is it worth thinking about it from the other side?
That is, static is going to build up, and it’s going to be discharged. There’s lots of methods here for improving the frequency of the discharge to hopefully reduce the ‘spark’.
How about accepting that static will happen, let it happen, and figure out a way to make the static not affect the Shapeoko board? C3D have already mentioned that the newer boards are less affected by static, so there’s some sort of circuit design changes that can be made to make static less of an issue.
I’m not sure what this might be, but one thing would be to use an opto-isolator board between all stepper motors and the control board, and connect the control board to that via a heavily shielded cable, perhaps a meter or so away. This way there would be no electrical connection between the controller board and the machine.
Mark, try this.
Start with anti static dust collector hose, the kind with a wire wrapped around it for the entire length of the hose. At the router end, solder a length of copper wire to the end of the hose wire and secure the other end of this wire under a screw on the HDZ. This copper wire can be insulated or not, but it should be stranded because it needs to be flexible since it moves with the machine. Using a second length of this wire, secure one end under a screw on the HDZ (use the same screw if you like) and run this wire through the gantry drag chain and secure it under a screw at the end of the gantry. Run a third length of copper wire through the other drag chain. Secure one end under a screw at the end of the gantry and connect the other end to the chassis of the machine. I used one of the screws that holds the cover plate over the controller board. Run a fourth length of copper wire from this screw to ground. I connected mine to one of the grounding screws inside an electrical box on my cabinet. Now at the other end of the dust hose, connect this end of the hose wire directly to ground. Use your own judgment here of course, but I simply used the ground conductor of a three conductor extension cord. I cut the hot and neutral prongs off the male end and inserted the ground prong into an electrical receptacle.
The purpose of all this wiring is to get all the components of the machine and both ends of the dust hose to the same electrical potential (ground potential). The V-groove wheels that carry the Z-axes carriage and the gantry are made of non conductive material and thus leave no conductive path to discharge the static electricity. This wiring provides such a path. The router itself has a metallic connection to the HDZ so it’s fine the way it is.
This method put a complete end to the static electricity problems I had previously. I have not tried to mill PVC as you have but I have done some work with acrylic and I just completed a 16 hour job cutting MDF. The relative humidity in my shop is about 40% (it’s dry here on the Canadian prairies in the winter time).
I hope this will be useful to you and others.
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Someone needs to build a fixture that attaches to the bottom of the spindle mount, the fixture would have a partially enclosed spring-loaded ball-bearing with a wire out the other end to ground. (Maybe even sub the ball-bearing apparatus with a spring-loaded vinyl blade apparatus, carbide shaft should be harder than the blade anyways, but then maybe inadequate surface area may come into play.) That ball-bearing apparatus can then ride the exposed endmill shaft and collect the static charge to ground.
Static from PVC>to the cutter>through the shaft>to the ball-bearing>up the metal spring>through the metal backstop>through the backstop-connected wire to ground, all fixtured to/suspended from the spindle mount. This works in my head anyway…
Not a bad idea! The only problem I see with it is if you have a tool path that uses almost the entire length of the tool. If you have a pocket cut and the cuts are close quartered then you will have an interference issue with the conductor to the work that you will need to take into account. It might be better to ground from the other side of the amateur thus avoiding the issue altogether.
I just opened up my DW611 and there isn’t much room to do this kind of a mod, though it is possible but probably not advisable.
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Are you describing a DIY slip ring? Ball bearings don’t have continuous electrical contact, though maybe often enough for this application to prevent charge buildup. I have made a version of this before with pure silver paste in roller bearings to reduce discontinuities - it worked so-so, and would have to be sealed in this application. It might be easier to just ship the ball bearing and apply the metal wiper directly to the end mill.
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Everyone is talking about grounding the machine. Have you ever grabbed a doorknob and had a good shock?
In your shop what kind of clothes are you wearing? Clothes, like sweaters that generate a great static charge? Ground yourself if you have that much static in your shop. They make grounding straps with expandable wrist bands and banana jacks to plug into a good ground.
Also, very dry air (winter heating of the shop) will increase the chances of generating a large static charge in many different materials.
You mean I’ll have to stop wearing my tutu and slippers? 
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For effective static control, you’re much better off not wearing any clothes!
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in which case this warning applies on a whole new level:
(sorry, too much ? couldn’t resist 
)
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It would then be a shrinkie dinkie.
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There is just no explanation you could give at the Emergency Room…
“Big fan of science fiction are you sir? Perhaps you should wait for ComicCon?”
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I don’t know what a slip ring is, but from what you described that would be functionally what I was intending. I also would not have guessed that ball-bearings held against a surface through spring tension wouldn’t maintain continuous electrical connection, interesting. But, as you said, even intermittent connectivity should suffice in this application.
And an armature that just applies lateral pressure against the shaft (like the wiper of a potentiometer, or the springy metal connecting a bumper-car to the grid) may be better, though working out how to keep it in fixed contact would be trickier…
But, yes, the point of the fixture would be to siphon the static charge through the cutter, via connection with the shaft before it enters the collet/nut assembly, to a ground path, that was the idea…
I don’t think his problems are happening when he touches the machine.
@dclark when I saw this thread I thought the same thing, many posts on the internet talking about static buildup via the dust collection system as dust travels very quickly through plastic hoses or peoples DIY PVC pipes. Perhaps it’s the static build up through the vacuum hose.
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That’s a bit pejorative. Care to explain the reason to dismiss 75 posts?
Have surfaced HDPE, which I believe is similar. My vacuum hose has a bare ground wire running inside it, which is grounded to the machine chassis, and I have a bonding wire between Z, Y and X through the flexi track. Not connected to mains earth (unless the VFD does this). Might be asking for trouble here, but I’ve not seen a static disconnect yet…
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I surface the PVC filler strips on my machine quite regularly, but do it w/ a #201 since I don’t have the endmill specified in the first post.
EDIT: to expand as @downrazor11 did:
I use either a Sweepy v1, v2, or a 3D-printed dust boot all of which have a bit of foil tape added so as to make a ground connection from the body of the router to the conductive hose (thus far I’ve tried two different hoses, the Festool one which was bundled w/ my CT Midi and a Fulton 2.5" conductive hose https://ptreeusa.com/dust_hose.html connecting to a conductive angle from the Oneida Air folks) which is connected to my Oneida Ultimate Dust Deputy (second generation of conductive plastic w/ grounding straps).
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I haven’t surfaced PVC, but I am another that has surfaced HDPE (twice in the beginning of Jan) and regularly work with acrylic and PVC without ever having a disconnect, with the caveat being that that surfacing was done before I received my Sweepy 2, then I was just manually holding a vacuum hose tube close to the cutter… By responding I have probably jinxed myself…
I currently have the Sweepy 2 with a hose up and over to a shop-vac on another circuit with no special grounding anywhere. I run my SO3 in the ground level of a house built in the 1910s, and my relative humidity is 24% according to a digital thermometer.
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