RE: [CAD_CAM_EDM_DRO] Static electricity - WOW

You won't need a large wattage resistor for the hose ground. 
 
Do not put a resistor on the ground line from your CNC to ground as this defeats the actual purpose for that ground.  One reason the ground line from the machine to earth is there is in case there is a short somewhere from the high voltage to the machine chassis, should that occur with that resistor inline YOU would become the easiest path to ground rather than the ground line and could possibly injure or even kill you (depending upon the voltage you are using).  Also, even though code doesn't always require it, the ground wire from your circuit distribution (breaker) panel should be the same gauge as the "hot" wires, if they are much smaller and you do get a short circuit to the chassis, the smaller wire could easily melt again leaving YOU as the easiest path to ground.  I guess it goes without saying that the ground wire to the machine is also going to bleed off any static electricity built up during operation 
 
Never assume that your conduit (even if it is metal) will supply sufficient grounding for a machine, always run a separate ground wire to the machine.

Randy Abernathy
CNC and Industrial Machinery
service, repair, installation and
design

4626 Old Stilesboro Rd NW
Acworth, GA 30101
Fax: 770-974-5295
Phone: 678-982-0235
E-mail:
randyabernathy@...

--- On Mon, 2/22/10, Jack McKie <freshwatermodels@...> wrote:


From: Jack McKie <freshwatermodels@...>
Subject: RE: [CAD_CAM_EDM_DRO] Static electricity - WOW
To: CAD_CAM_EDM_DRO@yahoogroups.com
Date: Monday, February 22, 2010, 4:14 PM


 



Jeff,
 
Interesting solution.   Can I run the ground to a water pipe or the ground in the electrical outlet?   What wattage should the 1 meg ohm resistor be?
 
Jack

--- On Mon, 2/22/10, Jeffrey T. Birt <birt_j@soigeneris. com> wrote:

From: Jeffrey T. Birt <birt_j@soigeneris. com>
Subject: RE: [CAD_CAM_EDM_ DRO] Static electricity - WOW
To: CAD_CAM_EDM_ DRO@yahoogroups. com
Date: Monday, February 22, 2010, 3:41 PM

 

The small chips and bits of debris running through the inside of a plastic
hose happen to be a perfect medium to generate static electricity. Since the
static electricity is generated by the difference in potential between the
inside and outside surface of the hose (sort of like a capacitor) what you
need to do is equalize the two surfaces and provide a path to (earth)ground.
Some folks try to run a bare copper wire up through the middle of the hose
but all that does is cause lots of blockage by stuff getting caught on the
wire. What I have found works really well is stitching come 24 gauge copper
wire through a hose rib about every 8 inches or so. Just look the wire from
the outside of the hose through the inside around a rib. Stitching around a
rib keeps the wire from ripping a hole in the hose. A bit of silicone
sealant will seal it up well. Hook the duct collector end of the hose to
(earth)ground and your set. Running an (earth)ground to the aluminum table
of your router might help as well.

One last note: when running (earth)grounding leads like this for control
over static electricity it is always a good idea to hook a 1 meg-ohm
resistor in series right at the connection to the (earth)ground rod. This
keeps the wire from becoming a potential hazard by provided a low resistance
path between a high voltage source, through you, to (earth)ground.

Jeffrey T. Birt

Soigeneris.com

304 Fox Creek Road

Rolla, MO 65401

573-647-9294

From: CAD_CAM_EDM_ DRO@yahoogroups. com
[mailto:CAD_ CAM_EDM_ DRO@yahoogroups. com] On Behalf Of Jack
Sent: Monday, February 22, 2010 1:33 PM
To: CAD_CAM_EDM_ DRO@yahoogroups. com
Subject: [CAD_CAM_EDM_ DRO] Static electricity - WOW

I guess I have a static electricity problem. While cutting a model boat
stand on my router I was using a dust collector . I was holding the
hose by hand. Something touched something else and both I and my
computer got a jolt of static electricity. Has anyone else run into
this? Cures???

I am assuming I need to ground the router which is aluminum on a wood
stand. Do I need to somehow ground the plastic hose on the dust
collector?

Any suggestions, insight, etc. appreciated! !!!!!!!!! !

jack

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