Grounding Dust Collection System

[JoeinWestMich]

I am getting ready to add the dust collection hose to my new Buddy this weekend. I have plenty of 4" hose with the wire running within it. I was going to hook up a piece of the hose to my Jet Vortex cannister system, hook this hose to PVC tubing that will run up the wall of my garage. A 90 degree elbow will be used to connect a straight PVC pipe to run along the ceiling until it gets over the Buddy with another 90 degree elbow connecting to a piece of 4" PVC pipe that will drop down from the ceiling a bit. I will connect the 4" dust hose to this and bring it down to the Buddy. The manual says this needs to be grounded. I have been reading a bit on the internet via google search but still have not seen a solution that everyone agrees upon. So I thought I would ask the brain trust here. Do I run copper wire along the inside of the dust system from the Buddy all the way through the inside of the hoses/PVC to a ground screw on the base of the Jet? Some suggested wrapping the wire on the outside of the system starting from the Buddy and going to the ground in the base of the Jet. Thoughts? As I install this PVC, I am going to extend it to go to my table saw and jointer. Will I have to ground those extensions in the same manner to protect the electronics of the Buddy? This is beginning to be quite the project.... thanks for any input you may want to share.
Joe

[coryatjohn]

I have a Oneida V2000 system. For grounding, I used the steel wire in the flex pipe grounded to the spindle on one end and the V2000 mail frame on the other. All the other parts to the system (both ShopBot and V2000) have copper grounds run between them and all those grounds lead to a proper ground for my shop's electrical system. So far, I haven't seen any issues with this setup and it seems to be very good at handling static charge dissipation. I'm sure I could have gotten a lot more fancy.

[jTr]

Joe,
I fought missing com issue for almost a full year with my bot. Tried everything I could think of, until finally trying the right thing, with the help of others here as usual. For the longest time, I was convinced the wire reinforcement moulded in the hose was enough, as it was connected to a discharge point at both ends - tech support agreed that should be ok. Brady pointed out that a wire must be present inside the flex hose in order to provide a continual discharge point as the material flowed through the hose.

1> Static charge inside duct hose will disrupt communications between your Shopbot control box and your computer. Run a thin copper wire through the entire pathway from the bot to the next piece of metal in your ductwork. That piece of metal should then be grounded to your breaker box. On the inlet end, just be sure the wire is secured but not attached to any metal portion of your Zcar/motor assembly (=ground loop potential = lost comm). Since doing so, I have 100% ELIMINATED lost comm issue.

2> There are numerous debates about the dangers of using PVC for dust collection and the potential for fire. In lite of that, it is advisable to run copper through all ducts to all machines.

Observation: I have all metal ductwork with the exception of short flexible connections to machines in my shop. I had a small sander that would periodically hit me hard with static discharges when my hand was within an inch or so of the clamp. I mean it hurt! Imagine the effect of this hit on your shopbot.

jeff

[feinddj]

Pvc is for water only. Don't use it for compressed air or dust collection. For dust collection, use smooth metal duct with wide bends where ever possible. Flex hose is for short runs to a machine especially if it moves or gets moved. Using long lengths of flex will reduce your airflow and limit your ability to collect the chips you want. The metal duct should be grounded all the way back to the dust collector.

You know those stories you used to here about grain silos in the midwest blowing up? They were caused by static electricity in the presence of dust.

Think of it this way. PVC generates static better than rubbing a balloon on your head. Static electricity plus dust equals a fire or worse, an explosion. I use the Nordfab duct and like the way I can reconfigure quickly without much fuss.


David

[jTr]

Another little known but very reasonable resource for spiral dust collection duct and fantastic prices for industrial gates and flex hose is the Blastgate Company.

We all know budget constraints are no small objection to overcome.
Think of this project just as any project you work on for your clients: The labor is the most significant and preciously scarce element involved.
Do it once. Do it right (safe), and you'll be rewarded every day after as you benefit from the results.

jeff

[dana_swift]

Rather than PVC try cheap sheet metal clothes dryer ducting is a much better option, as it can be grounded. Any of the big box hardware stores have it.

No insulator can be grounded by definition. The electric charge cannot move through or on an insulator. Thats why the wire helps, but it only discharges the air that comes in contact with the wire because the air itself is an insulator. Turbulence in the duct brings much of the air into contact with the wire which is a good byproduct of the turbulence.

As to the wire going through a plastic spiral hose not providing ground.. that is true in most cases because inexpensive hose is made from non-conducting plastic. It is possible to buy hose that is conductive enough, but its hard to find and not cheap. A wire through the hose is a good compromise. Conductive plastics can be grounded because they are conductive. Conductive coatings work also. The current flow from static is very low, but the voltage builds up linearly with time until breakdown occurs somewhere, the air ionizes and discharge can occur.

Hold on to an insulated hose.. you will notice that discharge effect real clearly.

D

[gerryv]

John, what do you use to bleed off the static that builds up through friction in the plastic flex hose, being that the steel coil is encased in the plastic?

[coryatjohn]

Gerald,

I think it's less of a problem for me because of the high humidity in Memphis. It's rarely below 50% and often much higher.

I agree it's a good idea to put the wire through the flex pipe. It's just not necessary for my installation.