Static Electricity

[VoxLimbo]

Don't connect your ground to plumbing pipe without checking your local codes. This is a safety issue for your plumber. The NEC covers proper grounding, but your local building codes may differ.

[ConKbot of Doom]

Originally Posted by keithorr Well, I'm glad to have read all this. My cable shield is unattached at both ends, even though the documentation states that one end should be grounded (at the controller end). A back up cable has the ground lead intact, but it was a stock lead from the manufacturer. I started to doubt the setup until I read through the installation notes. I'm using an open loop stepper system, so I don't have to worry about an encoder feedback suffering from noise. The thinking at the time by the installer was that noise wasn't going to be as big a risk as a line voltage short. What was a factor is that I dry mill graphite. The thinking was to keep the machine isolated from the driver box as much as possible, since live (not noise) current might find it's way from the spindle, to the machine, to the cable shield, and back to the controller. The machine is enclosed, and the enclosure is rife with graphite dust when things are going, to the point sometimes you can't see anything trough the window except a black cloud. There is good exhaust ventilation, but it doesn't always keep up with the amount of conductive airborne particles that end up coating every possible surface and void. If the cable shield was grounded to the driver box, and the graphite dust made a connection between the shield and the machine, I would have the straight line connection that HuFu mentions in his previous post. I was told at the time to make sure the machine was grounded well, and keep the driver box as isolated as possible. I apprecitate that there are standards, but one size may not fit all. If I didn't refer to my vendor notes, I might be tempted to reconnect the shield ground.

Either you have it isolated or you dont... If you have it 'poorly isolated' then any static will follow that path, waiting to kill whatever it can first. Grounding the frame will keep any voltages from going back to the controller. From the bearings bolting together castings/frame parts, there is always metal on metal contact, so everything should be interconnected, and the bearings should be fine conducing trivial amounts of current from any static. Ideally you would have a ground-steak right next to the machine, the frame would be connected to that, the controller box connected to that, the shelds on all cables would be connectd to the ground in the controller box, but not to the frame to prevent ground loops...

I'd rather have a well grounded machine then a machine isolated as best as I could get, because with enough static, it could arc though to the motor windings, or though insulation on a cable at some point, where a grounded machine would bleed off any charge before it could build.

[thkoutsidthebox]

Simple question: My machine is wood, and my controller box is plastic.....If I dont touch the steppers while running, do I need to worry about grounding?

[Al_The_Man]

I personally would ground all electro/mechanical equipment to a common ground point, not necessarily because of safety, but also noise prevention.
Al.

[FanucIssues]

Good grounding makes me happy.

[WolfmanJack13]

Originally Posted by Al_The_Man I personally would ground all electro/mechanical equipment to a common ground point, not necessarily because of safety, but also noise prevention. Al.

I totally agree with Al. 30 years as an electrician and technician tells me absolutely ground any metal parts such as frames, motor housings, etc. Control wire(shield grounding,etc) for noise is a totally different issue. Improper, partial or bad grounds are the cause of more injuries and fatalities than any one other electrical failure.

[Mazaholic]

I have never seen a motor without a ground wire or ground terminal inside the connection box.
Maybe i'm just not familiar with all motors,but grounding them seems to be the norm.
I have a six foot copper grounding rod thru the foundation beside every machine and the ones that have a ground bonding it to the breaker panel are grounded to both.

[Mazaholic]

Tip for anyone wondering how to drive a 6 foot grounding rod without killing yourself with a sledge.
Drill the hole thru the slab with a concrete drill then use one of these
http://www.harborfreight.com/cpi/cta...emnumber=93853
Or any cheap one you can find at an auction,flee market,or pawn shop.
Just make sure it accepts 1/2" dia. rods.
Put the hammer on the end of the rod,turn it on and let the weight of the hammer do the job for you.
Your arms will thank you and so will your machine.