Your OP really didn’t mention anything about dust collection until this post. PVC running through a dust hose will generate a huge amounts of static regardless of humidity, though with less it will be worse.
Time to divide and conquer! You need to isolate the cause of your disconnect issues. From the sound of things it’s your dust collection but you need to verify it. Try running the same program (air) with the router on and no dust collection running. If you have a disconnection it’s electrical noise.
If no issues then with the router off run the same program and place as much PVC shaving as you can through the dust collection. If you get disconnection you need to add a drain wire to your dust collection and make sure it’s connected to everything on the machine and to ground.
Moreover my hose was only touching the sucky dust boot while I was doing the surfacing. So if it discharged it had to somehow be through sucky.
I have probably generated 100lbs of pvc dust (and 100lbs of acrylic dust as well) in the last 4weeks (cold and dry here) using a 1/4" endmill and contour toolpaths. No issues there. Only surfacing.
I’m not complaining about this at all really, its a really specialized use case. I would just be curious for someone whose done the extensive static fixes to just run a surfacing toolpath with a 1" endmill on some PVC and see if they can do it without a disconnect.
The surfacing bit is reasonably big, I presume? Perhaps that increase in surface area is the difference here?
There was a comment about movement causing static… that’s not exactly true. Static is caused by reallocating free electrons and is caused by rubbing a conductor against a relative insulator… if I remember high-school physics when sheepskin was rubbed against a plastic rod (not a euphemism)
A mad idea is to attach a bit of stiff copper wire - earthed of course - to the spindle mount so it rubs against the top of the plastic stock and is a few millimeters from the spinning surfacing bit… a bit like the thing that powers bumper cars.
EDIT: The idea is that the static is actually building on the surface of the insulator (the plastic being cut) until it reaches a level where it sparks. So we need to get the electrons from there to ground.
If I run those copper wires to an LED controller I should in theory be able to make some LEDs light up if its the amount of static I think it is right? LED and controller are 5V
Because you could probably do 1/2" without any issues. I can push 1/8" DOC at 200ipm and setting 1 on the router and get 0 drama. But I thought of that and tired .0625" DOC and got the same result.
@sixstring so I didn’t quite do that tonight, mostly because I don’t want to create a mess. But here’s what I did do.
Directly before this video, I cut what i needed to out of this piece of scrap and used a 1/4" o-flute to do the surfacing. No issues. RIGHT AFTER I again used the 1" Whiteside Surfacing Bit to surface the remainder of the scrap to just do a test to see if and get a disconnect, and sure enough about 90 seconds in to surfacing it cut out.
The stock in this case was mounted on top of 1.5" thick piece of Acrylic (Its for a job I’m cutting tomorrow). That said I’m pretty sure acrylic is a great electrical insulator and cutting on top of it further isolates the S3 from creating a way for this to ground say through the spoilboard mounting hardware. Finally, the hose to the vacuum is touching the Sucky Dustboot with a rubber tip, the 1.5" acrylic below it on the Y- edge of the machine, the routers power cord (router plugs into vacuum), and my home’s wood floor (machine is on the ground). All this was the same during both the 1/4" and 1" bit surfacing operations. Yet the disconnect only happens with the 1" bit.
My solution was to purchase a couple of extra power cord EMI filters and put them on the router power cord. Then move the power cord up and away from all wiring on the gantries. That solved my issue
Well you have a repeatable issue, that’s the first step to a solid fix.
The whiteside bit is larger, has a higher surface speed and a lot more contact area to develop static in the friction between the bit and the workpiece. You’re quite correct that both the PVC and the acrylic are very good insulators and will allow a large static charge to build up on the surface of the workpiece. No amount of grounding will usefully prevent this charge buildup, it’s a fact of life. If you really needed to suppress this then a fogbuster spraying a slightly conductive coolant and a conductive base such as aluminium would likely be the way to go.
On my machine the cutter is already grounded as the spindle is grounded and the spindle bearings conduct to the collet well enough that I don’t actually need the croc clip for the bitzero. Grounding the cutter does not reduce static buildup on the workpiece, it just bleeds away the charge on the cutter. The workpiece and the chips still build up and hold charge if they are an insulating plastic.
The likely paths for your cutout are
Static charge buildup on the insulated rotor of your router (from the cutter) reaching a high enough voltage to discharge to the windings or brushes of the router and send a spike back down the power cable, creating EMI and upsetting your USB connection
Static charge buildup on the surface of the workpiece reaching sufficient voltage to discharge to the shapeoko frame and then jump to ground via the controller board, stepper motor wiring etc. and causing a USB disconnect that way (could also be via the router frame)
The charge on the chips is going up the festool hose and presumably that anti-static hose is grounded somewhere else? (but this still leaves the charge on the workpiece)
My bet is the discharge through the frame, did you run a ground wire to your router mount / Z axis yet? Did you test conductivity to ground for the main parts of the frame? (X beam, Y beams etc.)
Like Will said in this thread, support tracks these issues when reported. Browsing the forums, I feel that chronic disconnects among these units are still statistically rare. Some folks disagree. So if it helps, let’s crowd source the situations where disconnects are happening, so we can do some failure analysis. Aside from outliers, surely we can narrow down to a few primaries… and then these disconnect threads could get a lot shorter.
My Situation
I rarely have any trouble with disconnects. Except when jostling the usb cable while running, anytime I have experienced a disconnect so far was under very specific circumstances: winter (didn’t think to note relative humidity), 1” surfacing bit, mdf, shop vac sucking huge amounts of dust through noncollapsible flexible silicone hose, pwncnc boot, carbide unbranded trim router. I haven’t experienced DCs when using any other cutting bit with the same variables. I also haven’t applied any specific measures like conductive tape, extra grounding wires, UPS, etc.
Humidity, cutting bit, dust collector hose, material being cut, router/spindle, dust boot, grounding steps already taken/changes, repeatability… just a thought.
I found some interesting info on dust collection and static buildup that has interesting references. This article doesn’t directly cover the issue that @MarkDGaal is having, but interesting nonetheless: Grounding PVC and Other Dust Collection Myths
Perhaps there’s some helpful insight in there somewhere.
Maybe it is a misuse of wording.
. You can “ground” the conductive materials of the machine by running a conductive path to ground, then apply a collector to the non-conductive elements and run that to ground.
More explicitly, appling a conductive element to collect the charge and then sending that charge through a path of less resistance to ground (for non-conductive materials).
Maybe consider changing out the bristles used on the dust boot to a set with grounding bristles…bristles added to collect static, mod the boot housing with a grounding strip that can be attached to a ground source.
This is good! at least the rest of the group can see what’s going on. I think Liam is on to something with the static build up on the workpiece. I did not think of that as I have not worked with this type of material before. The work is completely isolated and acting like a battery being charged.
I like the idea of an anti static lube spray on the material itself and given your feed rate is somewhat aggressive it will aid in keeping the tool and material cool. I would still go through the entire machine and check for ground continuity on every piece!
I just went through my S3 and rebuilt and upgraded to a Z plus and apon resurfacing the MDF waste board with a 1" bit I had all kinds of disconnects. I’m running 2 1/4" Kent shoe with a 750 CFM 2 stage, I forgot to ground dust collection… simple fix and no more problems.
When you are dealing with static electricity look at an electrostatic series chart. PVC is way down at the bottom of the chart which means if anything higher on the chart that rubs it, static will build up. Wood is about 2/3 up on the chart.( MDF could be even higher but I could not find it) If the PVC is vibrating a little against the waste board it will build up static. High humidity is often used to neutralize static(wet gloves not just your hand) but not good around the waste board. One thing that can discharge static is strong UV rays. Might need to get special glasses. However I am not sure how much it will cure the static problem. Might be worth the try if you have a powerful UV light. One thing I have done was put very sharp points on a electrostatic generator and the sharp points eliminated the static. It would not build up. Wrap your router with a large hose clamp and put small sharp nails through the clamp before tightening. Physic teacher, Electrical engineer talking.
