Reducing dross on 3mm plate cut

[visor_down]

Hi all
Any pointers on reducing dross? I am cutting 3mm plate and getting dross that is harder to remove than shown on numerous youtube vids.
I can remove it but have to tap it with a chisel (held in hand not hit with hammer) perpendicular to cut, rather than just being able to run something down the edge in same direction as cut and it just falling off.
I have tried more amps and varied travel speed , if I go faster it blows back , air pressure is set as per manual.
Is there a very fine window for less dross or at least dross that is easier to remove?
Out of about 3m of cut I had about 50mm that didn't have dross! I'll be damned if I can work out what I did differently on that 50mm bit!

 

[MattH]

My experience of plasma cutting is the same as yours.

 

[dannyp]

on my cheep plasma i found the best setup was acheved ignoreing the manual need to play with amps and air pressure. i get a cleanest cut useing a guide and going quite fast

 

[Jim Davey]

Matching amps to a high enoug travel speed is the ticket.

 

[langy]

I suspect your using too little air pressure, when I first got mine I got told 40psi but found it left dross, increased to 60-65 and got none.

 

[Davek0974]

The air pressure should be specified by the manufacturer.

Yes the dross-free window can be very small, maybe impossible sometimes. I run a small CNC table and can sometimes get dross-free cuts on the straight but forget it on curves etc. The dross i do get is easily whipped off with a rotary wire cup brush on a grinder.

I cut a lot of 3mm sheet and using 45A you would need to be moving at around 4000mm/minute.

 

[Gareth J]

I suspect your using too little air pressure, when I first got mine I got told 40psi but found it left dross, increased to 60-65 and got none.

Interesting. I have similar experiences to all above. The book on my plasma-part one says 40psi and the chap on the phone at plasma-part I spoke to for advice also said to stick with 40. Any lower and things start to melt as there isn't enough cooling air. He didn't say what happened if I increased it though. I might test increasing it. Perhaps it comes at a cost to tip longevity.

Seems like a lot of variables to fine tune easily.

 

[Wendelspanswick]

I vary the air pressure on my CUT50 from 45psi up to about 62psi depending on the thickness of the material being cut.

 

[langy]

Interesting. I have similar experiences to all above. The book on my plasma-part one says 40psi and the chap on the phone at plasma-part I spoke to for advice also said to stick with 40. Any lower and things start to melt as there isn't enough cooling air. He didn't say what happened if I increased it though. I might test increasing it. Perhaps it comes at a cost to tip longevity.

Seems like a lot of variables to fine tune easily.

I find the tips last longer with higher pressure John, I reckon my tips last generally 2-3 months and probably use my cut50 3-5 times a week, I tend to use it more as the thin cutting discs cause so much dust

 

[skotl]

FWIW I find that most of the dross can be easily chipped off with a hammer, or even sticking the dross in a vice and cracking it off, rather than having to go straight to the grinder.

 

[Davek0974]

AFIK its all about arc power density, less air and things will melt, too much air and you have less power as the flame will be less dense due to the faster moving air flow, way too much and you can blow the arc out.

Yes there are a million and one parameters in plasma cutting

 

[langy]

FWIW I find that most of the dross can be easily chipped off with a hammer, or even sticking the dross in a vice and cracking it off, rather than having to go straight to the grinder.

You shouldn't have to take a grinder to it, a tap should see it fall off

 

[visor_down]

Cheers all my manual (RTech P50HF) says to use 50psi all the time and 20amps upto 6mm. At 3mm I tried 35 amps but didn't improve dross.
Clear from the comments I am not alone so least I know it just a case of trying to find the right combination. More practice me thinks!

 

[BrokenBiker]

i know very little about plasma cutting, have very limited experience with it but have used a cut50 a few times, and found that after it was set up by the guy that knew what he was doing, if i knocked the amps up a touch, air pressure up a touch and travelled falt out i got dross that came off lovely and easy with the rake of a chipping hammer/scrap bit of bar

 

[dannyp]

problem is those cutting capacites look very optomistic to me.

18mm with 50 amps really ? it might eventualy chew a nasty goudge through. IMO 50 amps will cut 10mm mild accseptably, but cuts 6mm well as in it's a dross free tidy square cut at a good travel speed

 

[Kent]

Things like this often just need playing with one variable at a time

 

[skotl]

Things like this often just need playing with one variable at a time

That's it. Nothing more scientific than that

 

[Kent]

That's as scientific as it needs. Easy to confuse the matter second guessing or changing multiples at once

Try one thing if it don't help change it back again. That's the bit most miss daft as it sounds.

When you have it working good write it down. My shop wall is full of such notes

Leads for rollers
Settings for commonly welded materials

Memory often let's me down and if I put it in a book I should likely forget were I put the book lol