Auxiliary grounding wire

[nlancaster]

Hello,
We have a part that is a glue up of ceramic and titanium.
We have always used a grounding clamp attached by a wire to the fixture.
This grounding wire frequently brakes after months of use where the wire is crimped into a wire eye for mounting with a 6-32 screw.
I have thought for a long time the problem is the size of the wire, making it too stiff which causes extra stress at the mounting lug.
I think the wire is 12gauge stranded copper.
I have never seen more then 70v at 3-4 amps during the cut, so I should be able to go to a much lower wire gauge right?
I was thinking from what I know about electricity we should be able to go down to 14-16 gauge wire without issues.
The wire itself is fully submerged during machining which should help keep it cool.

Any thought or tips on this?

 

[KilrB]

I figure the manufacturers don't put itty-bitty ground wire on their machines for a reason.

I use an old one if those when I think I need some "extra" ground.

 

[Scottl]

Try to find rope-laid wire. This is a construction method that keeps even large gauges very flexible.

 

[SeymourDumore]

I think the wire is 12gauge stranded copper.
I have never seen more then 70v at 3-4 amps during the cut, so I should be able to go to a much lower wire gauge right?
I was thinking from what I know about electricity we should be able to go down to 14-16 gauge wire without issues.

Your problem is not as much as the size of the cable, rather the flexibility of it.
First, due to the high frequency, you'd need a fine stranded cable.
Fortunately: The finer the strands, the more flexible the cable is.
Unfortunately: The fine stranded cables typically only come in larger sizes.

Mcmaster has #6 as the smallest with a 259/30 strand: https://www.mcmaster.com/welding-cable/flexibility~ultra-flexible/

Do not solder the cable at the clamp, crimp it.
After crimping, see if you can encaplulate it with something that keeps the water away from the copper strands, even if it's Goop from a tube.
After that cures, put a shrink tube over it.

 

[Gordon Heaton]

You can get this for under $20: Super-flexible copper cable

It is extremely fine strands with an extremely flexible insulation. The insulation is silicone and I don't know how it reacts to EDM dielectrics.

 

[nlancaster]

You can get this for under $20: Super-flexible copper cable

It is extremely fine strands with an extremely flexible insulation. The insulation is silicone and I don't know how it reacts to EDM dielectrics.

This seems like a good product.

Thanks for the info everyone.

 

[SteveEx30]

Could just use a thin gauge stainless cable. Doesn't need to be copper.

Not talking about very many Amps here...

 

[KilrB]

As explained to me by a couple of Charmilles tech, it's high frequency and high frequency likes the surface of the wire not the core so ...
You need lots of small wires to maximize the wire surfaces.
Look at the cross-section of any power or ground cable on your machine.
One thin wire isn't going to do what you're asking of it.

 

[Gordon Heaton]

Could just use a thin gauge stainless cable. Doesn't need to be copper.

Not talking about very many Amps here...

Stainless is a lousy conductor though. Even a short length will have significant resistance which might mess with the burn somehow.

 

[Gordon Heaton]

This seems like a good product. . .

It is. I used it on my shop-built sinker servo head but I haven't immersed it in any type of fluid. The wire itself is very good, its the silicone insulation I'm not sure about.

 

[SteveEx30]

Stainless is a lousy conductor though. Even a short length will have significant resistance which might mess with the burn somehow.

I guess all my stainless tooling for the wire is a lousy conductor too

 

[memphisjed]

Tin plated grounding strap? No insulation, super flexible, all tiny strands.

AC/DC WIRE AND SUPPLY Tinned Copper Flat Braid Ground Strap Grounding 1" Width (15 FT): Amazon.com: Tools & Home Improvement

AC/DC WIRE AND SUPPLY Tinned Copper Flat Braid Ground Strap Grounding 1" Width (15 FT): Amazon.com: Tools & Home Improvement

www.amazon.com

Not endorsing brand, just example. Ground wires are generally oversized to provide the easiest path.

 

[Gordon Heaton]

I guess all my stainless tooling for the wire is a lousy conductor too

Of course it is! But, it is also pretty massive compared to 'thin gauge stainless cable'. Length to width ratio means a lot for a small diameter wire in electrical service. I don't know if that stainless cable would be a problem or not, but super-flexible copper would definitely work fine.

 

[Labrat]

I have some copper wire rope that you might find useful. It is left over from a contract build I did a while back. I'll send you some if you want.

It is 7x6/36gage, so 7 bundles of 6 36 gage wires. Overall diameter is .042 inches.

Sorry for the poor pictures, it is hard to zoom in that much with my phone.