Plasma cutter question

When using my plasma to cut some SS, I am able to cut it nicely, however on the bottom of the kerf sits welded balls of the kerf. Am I using to much air pressure ? or
is it to high current ?
I posted this last night but it didn't show up - I think my ISP is purging or not providing.
Martin
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Martin Eastburn
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consolidated dot net wrote:

Plasma cutting stainless always leaves a nasty jagged slag edge on the bottom. I have never found a way around it.
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Ernie Leimkuhler wrote:

I agree - I was concerned I had water in the mix (still) - have a mech dryer and a pressure valve that extracts water (so it seems prior to dryer) concern was spraying steam and cooled the SS.
Today I went from 40 to 20 back to 30 amps. At 20 and 25 there were some hit and misses - not enough electrons.
I'm going to try a few other exotic experiments when time permits. Lots of work when you cut out a long name and there are hundreds of welded balls.
Thanks - I'll keep the group posted.
Martin
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You can minimise the amount of melted-and-resolidified crud hanging to the bottom of a plasma cut of stainless sheet, but you will never (???) be totally free of it, using a shop plasma cutter using compressed air.
It is time-consuming and fiddly to grind it off while leaving no other marks on the sheet, for sure - takes longer than the cut itself and then some.
I have been told that if you are making a lot of things to the same design, the only (???) way to get your blanks with a clean kerf is to have them lazer-cut, where they will use pure nitrogen blowing as well.
Advice I got from some of the more experienced folk on the group.
Riuchard S.
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Or water jet...
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lionslair at consolidated dot net wrote:

Remember the Stainless Steel - and the ragged bumps of metal with oxide coverings after the plasma cutter cut a line ? - Tried some of the magic stuff : [ Seems likely nothing will unless a glass tape or the like - plasma does what it wants! ]
I finally unpacked enough boxes, trunks and cases and found the spray can of welding inhibit 'oil'. Man is that stuff thin. I sprayed a wave under the table and under the area where I was about to cut - it was there (near by) after the cut of the plasma - No - No effect to speak of. I appears to just be vaporized around the area. It does get hot there - blue steel and all of that for a boundary around the cut.
And in the digging, I came across a sheet of Al. - Man did that cut nice. It was 1/16 so it wasn't much of a task - but the edges were singed off to a very clean edge. On the floor was tufts of AlO2 maybe.
Martin
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Martin Eastburn
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On Wed, 18 May 2005 23:30:52 -0500, lionslair at consolidated dot net wrote:

I wonder what there is about SS and not aluminum that causes this problem? The alloy? Heat dissipation? Is it that oxides on the aluminum prevent adhesion of the molten stuff from the cut?
Have you tried backing the SS up with aluminum scrap so that it acts as a heat sink? Place the SS on some aluminum sheet and then cut through both?
It's an interesting problem. I wish I had a plasma cutter to try some experiments myself.
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Artemia Salina wrote:

I think the problem is the same as with trying to cut SS with a torch; the chromium oxide is very, very tough and the melting point is so high that it just don't melt.
The backing sheet idea may have some merit- I'll try it next time I cut stainless, unless someone else says it doesn't work.
John
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Artemia Salina wrote:

I think the alloys that make up SS - chrome and the like are the nasty items. Likely cool faster due to higher temp to melt.. As steel - carbon type that is doesn't.
Al had a little edge much like a saw would put - if only pushing... - the finger could feel it - but it was tiny. When I cleaned up the layer of wood and area of floor around the ground protection wood - I found splatters of Al and a lot of heavy oxidized stuff. Some larger chunks due to cutouts but one or two big splatters - likely where a plunge cut was made and the holding in position was to long for Al - but functional for SS.
I haven't tried to sandwich some, but did a fools stunt today : spotted some double sided 0.013" copper clad PCB. - the foolish thing was forgetting the composite contents. Epoxy is BAD when burnt. And a wind blew the gas back into the shop against the two fans blowing it out the door! Quickly I held breath and turned one fan around and that did the trick.
Now what - a Weather vane Go-NoGo 220 V cut off ? -
Anyway - after washing the stinky corner in water I detected a complete burn through and trace cut. Just I'll never do that one again. Guess I'll go the the local roofing house and see if they have copper sheeting. I bet not in this part of the woods. Maybe the up-scale houses use it.
Hum - rolls of to be formed gutter. That might be a source of copper sheet to make stuff from. More research...
Martin
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