Plasma dosent like underseal and rot?

[Spark plug]

Been doing some welding to a daihatsu fourtrack tonight, tried to cut the rot out with the plasma but the arc kept going out, even after cleaning the paint from the top surface.

Made sure there was a good earth etc, so cut it out with the grinder instead.

Cut the repair section from new 16swg and it worked perfectily like a knif through butter.

Do plasmas just not like underseal and whatever else was stuck to the underside of the jeep?

 

[the snooper]

you would have had to cut good metal and not the rot just the same as you cant weld rust

 

[graffian]

you would have had to cut good metal and not the rot just the same as you cant weld rust

I can sell you a roll of rust to weld it with, it's proper English rust none of this chinese stuff.

 

[Spark plug]

you would have had to cut good metal and not the rot just the same as you cant weld rust

It won't cut the good steal arround the rot either even if I clean the paint off to reveal shiney steel.

 

[chunkolini]

I had a similar problem cutting up an old hot water tank, lots of blow back and a messy cut.
The tank was badly furred up, my guess is that the underseal is non conductive and the plasma is not working on it properly.

 

[Spark plug]

I thort that would be the case but I thort there was mabey a solution.

 

[rich r]

my guess is that the underseal is non conductive and the plasma is not working on it properly.

Exactly - rust, dirt and underseal don't conduct very well, and you need current to flow for an arc to exist. If you scratch through to good clean metal, you'll find you can cut/weld along that line.

 

[Spark plug]

Exactly - rust, dirt and underseal don't conduct very well, and you need current to flow for an arc to exist. If you scratch through to good clean metal, you'll find you can cut/weld along that line.

I've got clean steel on the side I'm cutting from the underseal is on the other side.

 

[KemppiFrog]

Not sure I understand this. My old Cebora would cut without the earth clamp and was not concerned about quality of steel. It would also go indefinately with no contact to the work. Are modern machines different?
KF

 

[Spark plug]

Mine is an orlickon citocut 10i, the arc will start and it will cut but it stops if it doesn't get an earth within about 10 seconds.

 

[GrahamGKD]

Does the Oerlikon machine have a mode for expanded metal or mesh? On the Hypertherm the expanded metal mode keeps the pilot arc going - it might be worth a try if the mode is available on the Oerlikon?

 

[dannyp]

if found the indusral machens have a much more powerfull pilot arc that helps lots when cutting crap

 

[Andrew55]

Are you earthing to the same panel that you are cutting ? Sounds silly, but I would not expect to find a good contact between two different body panels given the amount that some makers bond bodywork etc.

 

[Spark plug]

Are you earthing to the same panel that you are cutting ? Sounds silly, but I would not expect to find a good contact between two different body panels given the amount that some makers bond bodywork etc.

The earth was about 10'' away on the same panel, the rear wheel arch. The arc was blowing out before the pilot arc was turning off.

 

[Wedg1e]

I have a Citocut 10i as well, not noticed it being that fussy about prefect cleanliness.

 

[Spark plug]

I have a Citocut 10i as well, not noticed it being that fussy about prefect cleanliness.

It isn't usually it cuts powder coated steel no problem. It's just this car body work with underseal on it has a sissy fit about.

 

[bigbadbugga]

Have you tried cleaning the nozzle?

I find with mine that when cutting crappy steel the blow back clogs up the nozzle and partially blocks the air jet.

 

[slimjim]

mine doesn't like filler, not when its half an inch thick