job sticking

[oggy]

I do my ally tig welding at work on a steel bench which is covered with an inch thick piece of aluminium.
The earth is clamped to the aluminium, The problem im getting is the work piece is sticking to this sheet, What would cause this ? bad earth ?, No way i can clamp the earth to the work piece, so what else can i do to stop this happening ?.
cheers

 

[brightspark]

I do my ally tig welding at work on a steel bench which is covered with an inch thick piece of aluminium.
The earth is clamped to the aluminium, The problem im getting is the work piece is sticking to this sheet, What would cause this ? bad earth ?, No way i can clamp the earth to the work piece, so what else can i do to stop this happening ?.
cheers

bad earth conection and its welding together. weight the workpiece down to get a better conection and make sure the ally bench top is clean

 

[oggy]

Thanks for the quick reply, I do flap disc the bench once a week to keep it clean, what would i weigh the job down with ? block of steel ?.
Depending on what part of the piece im welding, its sometimes only resting with on one of the small brackets touching the bench.

 

[gordon stephenson]

Strip the outer sheath from a metre of welding cable and wrap the bare wires round and round the job piece then clamp your earth onto the stripped wire, Thousands of copper contact points to the job and no arc strikes,

 

[pedrobedro]

Have a look at third hand on welding tips and tricks to help with the problem.

 

[hotrodder]

There's a thread about 'earthing' tricks here... http://www.mig-welding.co.uk/forum/showthread.php?t=30657&highlight=finger

 

[gordon stephenson]

At one time I even thought about stripping a load of old welding cable and weaving a "mat" about a foot square but as usual didn't get any further than the drawing board in my head!! would be nice to just put polished items onto it without damaging the finish in any way.

 

[oggy]

Thanks for The advice, i shall have a pley to find which one suits best.

 

[Tiggy_dorset]

At one time I even thought about stripping a load of old welding cable and weaving a "mat" about a foot square but as usual didn't get any further than the drawing board in my head!! would be nice to just put polished items onto it without damaging the finish in any way.

Hmm, quite like that idea. Maybe another to add to my 'unfinished project' list

 

[Shox Dr]

I don't think you can ever clamp the bench and hope the work piece will not mark through arcing.

When I was building SS canopies we used to make everything and spent all day making hangers, and it didn't matter if they arced, though sods law stated they never did. Low and behold as soon as you forgot to move the clamp to the work piece, for finished jobs the damn thing would arc up.

So for small items that would either not sat pity with the return lead clamped to it, a large weight was the next best thing, it also have the added advantage of stopping the work piece from moving about.

 

[oggy]

My problem is i cant really clamp onto the work piece as the clamps to big plus i have to keep moving it to add brackets, unions etc, Ive had some jobs arc as i have just about finished the job, resulting in blowing a hole in the core of an oil cooler or intercooler
Would a car battery earth lead attached to my earth clamp one end and a crocodile clip to clamp onto the work piece work ?

 

[hotrodder]

While copper is obviously miles better conductivity wise i suspect the 'copper mat' won't be much better in that it's still connecting to ally (or whatever the weldment is) and will still arc under some circumstances- never when it doesn't matter, always when it does!

My problem is i cant really clamp onto the work piece as the clamps to big plus i have to keep moving it to add brackets, unions etc, Ive had some jobs arc as i have just about finished the job, resulting in blowing a hole in the core of an oil cooler or intercooler
Would a car battery earth lead attached to my earth clamp one end and a crocodile clip to clamp onto the work piece work ?

Yep. As said to guarentee good contact/eliminate arcing you need some pressure as well a clean spot. When clamps aren't convenient that means weighing it down with something like a 'welders finger'

The first thing i do when working with heat exchanger cores is to tape cardboard over the fins as they're just too damn delicate. For example (not a rad that i made)...



The return clamp would have been clipped to the bottom tank, a mounting foot or the outlet tube

I took this pic a while after failing to find a decent close up of a fillet in the other thread. You'll have to ignore the 'mankyness' as it was just an adaptor knocked up to leak test something using a manky bit of tube etc



It's a -8 AN fitting welded to a couple of inches of 5/8 tube. While i didn't care about most of it i didn't want to risk arcing onto the sealing cone or threads so the tube was clamped to a bit of angle.

Another way i do things...

The bit of card means i can spin the tank around the table without worrying about scratching it, return clamp to another clamp for better contact with less risk of marring the tank with the heavily sprung return clamp. bolt holes are another favorite- spin a long bolt in, lock it with a nut and clip the return (or a smaller additional one) to that


Another thing you can do to save time with small things that move around (by design or accident) when welding them is to knock up an adjustable stand with a bit of weight to the base. You can then bolt or clamp the weldment to it and let the entire thing 'earth' through the table without fear of any arcing to the weldment- if it happens it'll get the fixture where it touches the table

 

[gordon stephenson]

As long as the crocodile clip is capable of carrying the full welding amps.