Common ground?

[outofstepper]

Sorry if this has come up before, but didn't see anything in search
results.

I do 90% of my welding / cutting at the same spot on my bench.

I'm wondering if its safe to connect all my machine grounds to the
table semi-permanently.. meaning tig, mig, plasma. I could do this
discretely i think in a little trench on shop floor. that way I only
reach for the business lead when I need it.

Do i risk doing damage to my other machines?

just curious.
Thanks.

 

[rtbcomp]

Should be fine, just make sure that the welding return isn't connected to the mains earth in any of your machines.

If there is an internal connection and the table gets connected to mains earth then there is a risk of stray currents burning the mains cables, and if the welding return gets disconnected the welding current will go through the mains earth.

As a further precation you could unplug the machines you're not using from the mains.

 

[Shox Dr]

I find that having just one Earth return lead for the lot is the safest way, saves all the cables on the floor if nothing else. I swap it over depending on what I'm using

 

[Drains]

It's fine. Connect as many machines as you like to the bench. The current has to go out to come back (electrons in=electrons out), so effectively a machine works within a closed loop, even if it's sharing part of the earth route with other machines. In shipbuilding you'll find hundreds of sets all using the ship's hull as a common ground.

 

[gavuk]

We "daisy chain" bench's etc ,just attach the earth clamp to 1table and either cable or weld steel between the bench's,,,,,,you mention a trench?, you could weld some flat to the bench run it across the floor to near the welders, rather than drag the cables to the bench for a more permanent connection ,or go upwards ,loads of ways to do it

 

[chunkolini]

I know F' all about this stuff.
But I have a distant memory of a comment I read somewhere years back along the lines of 'high frequency somethingorothers being able to track back up earth leads and damage thingummywotsits'
I think this was in relation to high frequency starts on plasma cutters and Tig welders. I apologise for using overly technical language.
Can anybody shed any light on this one, has been bugging me for years.

Chunko'.

 

[Shox Dr]

the tin foil has fallen off your head chunko

 

[Robotstar5]

It's quite common to have 2 or more robots working on a fixture with work returns connected together, the only time I had a problem was 2 TIG robots had problems when arcing up at the same time, something to do with the HF starts interfering with each other.

Losing the return can be an issue, I've seen robot internal wiring burnt out when the weld current tried to use the screen on the control cables - an expensive mess to sort out!

 

[Sparkey]

the tin foil has fallen off your head chunko

Yes, definitely!

'high frequency somethingorothers being able to track back up earth leads and damage thingummywotsits'

My 2 welding tables at work have built in fume extraction and they are linked together the way Gav' describes it, with a piece of flat...works a treat! It doesn't seem to interfere with the extraction system either...

The only thing that's bugging me is the flat connection is on the floor and when i sweep my booth all the muck get's stuck under the flat bar, that's all!