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Dumb Question from a VERY Green table owner

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Rickzink
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Dumb Question from a VERY Green table owner

Post by Rickzink » Sat Apr 02, 2022 10:10 am

I have a question regarding slag on the backside of my material. My cuts look good. Wire wheel cleans the front side up nice. I noticed there was a fair amount of slag on the backside of my cuts. I attributed this to the fact the I am blowing liquid hot metal through the bottom of my material. Seems reasonable enough that this would occur. I have been playing with the pre-set amps and volts and have cut down the amount of slag significantly. My issue is that the remaining slag is more difficult to remove that the more copious amounts of slag.

My question: Is there a way to get this smaller amount of slag to come off with less effort or is this just something I need to understand that I will have to deal with?

Thanks in advance for any guidance.

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Re: Dumb Question from a VERY Green table owner

Post by Scratch » Sat Apr 02, 2022 11:47 am

No such thing as a dumb question...

There will almost always be "some" bit of slag somewhere on a cut. It may not be everywhere though. Like you may get it on corners but not on straights or something like that. Your settings play a huge part in how much dross you get. Usually if I'm running too slow. You shouldn't get any on the front, and ideally, very little on the back. I usually get a little on the back, I run a wire wheel on a grinder over the entire front and back after the cut to remove any smoke, dust, and slag and it almost always comes off.

Sometimes I'll get a big chunk in some odd places and if I drop the piece on the bench, the flexing of the steel usually pops it off in one big chunk. Sometimes I'll cut with the wrong settings and get an unusually stubborn chunk of slag that one light hit with a chisel and hammer takes care of also.

A lot of people on here have great luck with a bath in acid or vinegar overnight to remove the slag, but I'm too impatient for that.

Mess with your settings and speed and you'll find the sweet spot.
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Re: Dumb Question from a VERY Green table owner

Post by robertspark » Sat Apr 02, 2022 4:31 pm

if you can. drop it drops side down on the floor from shoulder height.... may not work with thick stuff :)

I've not used acid but muriatic acid or caustic soda will apparently work, think it sides in pickling the steel too

wire brush on a grinder or flap wheel also works in my experience

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Re: Dumb Question from a VERY Green table owner

Post by robertspark » Sat Apr 02, 2022 4:32 pm

try testing your feedrate with a series of cuts to find the minimum dross setting for your plasma cutter

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Re: Dumb Question from a VERY Green table owner

Post by tinspark » Sat Apr 02, 2022 6:00 pm

After you get everything dialed in as mentioned above, some guys also take the extra step and spray anti-spatter (made to reduce dingle-berrieds for welding) . But if things are dialed in properly, I bet slag will not be that much of an issue to go the extra mile to spray the bottom of the sheet. I tried that method once to see what happens, but honestly I dont get enough slag (usually) to justify it.
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Re: Dumb Question from a VERY Green table owner

Post by adbuch » Sun Apr 03, 2022 12:39 am

Rickzink wrote:
Sat Apr 02, 2022 10:10 am
I have a question regarding slag on the backside of my material. My cuts look good. Wire wheel cleans the front side up nice. I noticed there was a fair amount of slag on the backside of my cuts. I attributed this to the fact the I am blowing liquid hot metal through the bottom of my material. Seems reasonable enough that this would occur. I have been playing with the pre-set amps and volts and have cut down the amount of slag significantly. My issue is that the remaining slag is more difficult to remove that the more copious amounts of slag.

My question: Is there a way to get this smaller amount of slag to come off with less effort or is this just something I need to understand that I will have to deal with?

Thanks in advance for any guidance.
What thickness are you cutting, and what plasma cutter are you using?
David

Rickzink
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Re: Dumb Question from a VERY Green table owner

Post by Rickzink » Sun Apr 03, 2022 9:00 am

Thanks for all the replies and guidance. The slag I have I have been able to reduce greatly. I get that it will have a little remaining. The small amount I do have is just extremely difficult to get rid of. Wire wheel won’t even touch it. I have to hit it with a grinding wheel.

My cutter is a hypertherm and I’m am mainly cutting 14gauge. I would like to market to some smaller fab shops as I know several that do not have those capabilities. We also cut 24 & 26 gauge galvanized sheet metal for duct. No issues with slag on that. Only on the 14gauge for some reason.

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Re: Dumb Question from a VERY Green table owner

Post by robertspark » Sun Apr 03, 2022 10:04 am

make sure you have fume extraction for the galvanized cutting

https://www.google.com/amp/s/www.cmac.c ... s_amp=true

and other links if you search

because the slag is brittle I've also been successful placing the material good side down on a flat steel bench and giving the slag a crack with the flat face of a hammer as that can separate it as the edge is hardened too if there is a slag lump.

one tap, .... not trying to drive the slag into the material just break the bond .... could also try a sideways glancing blow with a sharp wide cold chisel.... again just enough to break the bond.

I find that it's quicker than getting the grinder sometimes.

could try getting a 2 1/4 nch electricians chisel (bolster).... although you may not use them in America with wooden houses... it will provide a nice long level flat surface so you just skim the slag off

https://www.google.com/search?q=footpri ... =641&dpr=2

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Re: Dumb Question from a VERY Green table owner

Post by Joe Jones » Sun Apr 03, 2022 10:24 am

I use a 7" grinder with a 'YUGE wire cup brush. I screw down a zig-zag array of magnets onto a plywood board, and toss the metal onto the magnets. The wire wheel removes ALL of the dros, and it doesn't leave grinding marks. However, you absolutely MUST have a side handle on the grinder, and be able to control it! I wear a leather apron, to repel the dros projectiles that pelt me when they break off in my direction.

The biggest fear is that the wire wheel will grab something HARD and divert itself through my stomach on its way to my spine! :lol: But if you CONTROL the crescent of the wire cup so that it is always brushing OFF the edges rather than driving into them, it is fairly easy.

I would love to buy one of those wide belt sanders. A friend in Kansas has one. His metal is cut, and then run through the sander once or twice. It comes out so PURDY!

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Re: Dumb Question from a VERY Green table owner

Post by weldguy » Mon Apr 04, 2022 11:33 am

Sounds like you went from low speed slag (big, fluffy and easily removed) to high speed slag (thin, hard, and difficult to remove).

Continue to experiment with speeds, keeping the cutting height correct and document what is working best. You should be able to pretty much slag free on straights with some in the corners and on small interior cuts.

Plenty of techniques to remove slag, everyone has a way they like. I like the acid technique, its 100% hands free and does any amazing job with no grind marks or anything but you want your tub safely stored outside for sure.

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