Burnt edges when cutting stainless steel

[Pseudo]

Hi,
I have trouble cutting stainless steel, and can't get a clean edge
I a using a Hypertherm Powermax 1650, and everything is set as the manual suggest for this material
I've tried cutting 10mm and 2mm with the same problem
Is this normal? I feel like there has to be something I'm doing wrong

[adbuch]

I'm guessing that you may have a contaminated air supply. What do your consumables look like? Maybe post some photos. You need good clean dry air to your plasma cutter. Oil contamination and/or moisture can cause real problems with plasma cutting. In addition, make sure you have sufficient air pressure at the plasma cutter when your machine is cutting. For my powermax 85, I set the air pressure so that the pressure gauge at the air port on the back of the machine is reading 100psi while the air is flowing thru the torch.

David

[Pseudo]

Here's what the consumables look like
The last cut on the 10mm stainless damaged the nozzle a bit, so it was not as worn out as it is now while cutting

[adbuch]

Does this only happen when you are cutting stainless steel? I don't think your consumables look all that bad. What do your cuts look like with regular steel?
David

[Pseudo]

The cut on regular steel is pretty clean, especially compared to stainless
There is a bit of drooling (don't know what else to call it) but it comes of very easily, and it doesn't affect the quality of the cut
Here's what it looks like on 2, 5, and 10mm

[adbuch]

Those look much better, so I guess I would rule out air contamination. What alloy stainless are you cutting? It might be that you need to use an inert gas instead of air for your plasma cutter with this material. I don't remember if it was Argon or CO2 that I have seen recommended for particular applications. Perhaps a google search will help.
David

[adbuch]

Here is some information I found for cutting stainless steel. I don't personally plasma cut stainless steel (I have not had the occasion to yet) but perhaps some other members will chime in when the sun comes up.
David

"Argon-Hydrogen Mixtures are generally used for cutting stainless steel and aluminum. They produce a clean, high quality cut face."

https://espritautomation.com/plasma-cut ... ess-steel/

[Pseudo]

Thank you, I'll check this out!

[Pseudo]

According to this faq, the gas is definitely the issue, as we only cut using air

[weldguy]

In my experience stainless will never have as clean an edge as mild steel with air plasma however after looking at your pics you can improve a lot fairly easily.

Your air could definitely be cleaned up which will help and the nozzle in the picture is no good for anything. it's chewed up on the end and the orifice isn't even round anymore, also your electrode is near the end of it's life.

Use new consumables and be sure they are in perfect condition throughout the job. Get a good air filter dryer like this one shop/dryer_sharpe6760.html in front of your plasma cutter, and physically measure your cut height to be sure it is correct with feeler gauges, don't just trust that your on-screen settings are actually accurate.

All those things will help tremendously but please post back an let us know.

[Pseudo]

physically measure your cut height to be sure it is correct

Well... that's another issue I've been having, I can't find a way to set the cutting height, only piercing height and arc voltage control
The cutting software has every setting but this, and the THC only has rotary pots for arc voltage, IHS, and Pierce delay

There is a switch for manual up and down but if I put the THC in manual mode the position hold indicator lights up and the torch height won't move at all

So far I only assumed the cutting height was okay since I've managed to cut some pieces, but I have no way of putting the torch at it's cutting height outside of actual cutting, so I can't even mesure it

[adbuch]

physically measure your cut height to be sure it is correct

Well... that's another issue I've been having, I can't find a way to set the cutting height, only piercing height and arc voltage control
The cutting software has every setting but this, and the THC only has rotary pots for arc voltage, IHS, and Pierce delay

There is a switch for manual up and down but if I put the THC in manual mode the position hold indicator lights up and the torch height won't move at all

So far I only assumed the cutting height was okay since I've managed to cut some pieces, but I have no way of putting the torch at it's cutting height outside of actual cutting, so I can't even mesure it

Can you pause while cutting and them measure the height?
David

[Pseudo]

I just tried and the torch goes up immediately

[adbuch]

Can you do a dry run where the torch goes thru the motions of cutting the part profile, but does not fire?
David

[tnbndr]

When I cut stainless, not to often, it looks like your first pic. Pretty sure it is normal.
To stop your torch while cutting, do you have a panic stop button? Mine stops immediately where it is when I hit that red button.

[weldguy]

I just tried and the torch goes up immediately

If that's the case and your DRO shows the Z height when the THC Is on and making adjustments then cut a simple straight line on your stainless and read the DRO. When the cut is complete jog the Z axis down to the distance the DRO stated it was at when cutting and measure the torch height with feller gauges to confirm your DRO is in fact displaying the correct value. Hopefully it is and you can use your THC pot to get the torch down to that .020" cut height or whatever your chart says it should be.

[weldguy]

Can you do a dry run where the torch goes thru the motions of cutting the part profile, but does not fire?
David

Problem with that is the THC will not be active during a dry run so he cannot confirm the THC is maintaining the height he wants.

[djreiswig]

Can you do a dry run where the torch goes thru the motions of cutting the part profile, but does not fire?
David

Problem with that is the THC will not be active during a dry run so he cannot confirm the THC is maintaining the height he wants.

Good point.

[adbuch]

Can you do a dry run where the torch goes thru the motions of cutting the part profile, but does not fire?
David

Problem with that is the THC will not be active during a dry run so he cannot confirm the THC is maintaining the height he wants.

With the Plasmacam digital height control, which is what I am using - the ohmic sensor zeros to the material to facilitate setting the pierce height and cut height. The Z arc voltage shift helps to maintain the set cut height once the torch is cutting and corrects for irregularities in the material flatness. So for my system, I can do a "dry run" and read the set cut height from the screen, or pause it and physically measure the torch to material distance. This works as long as the material surface is flat and parallel to the x-y plane of motion. Of course, taking into account material surface irregularities, this test would be more accurate over the entire surface if the torch were actually cutting. With my table, I can pause while cutting and the z does not retract - so it is possible to use a feeler gauge or other gauge to actually measure the cut height when it is actually cutting the prescribed cut path.

I am not familiar with the thc the OP has, and you have suggested some good alternatives to him.

David

[arnegrant]

We cut 304 stainless and 316 stainless using dry filtered air (no special gas) and it looks about the same as mild steel.

Just fyi.

Reference pics with no clean up.

3/8" plate

Parts box, bunch of thicknesses

If I'm having trouble, I go to a 60 amp table in the book for the plasma cutter and dial the plasma cutter up to 80 amps (but use the 60 amp table and 60 amp consumables). And then I open the air to the highest pressure the torch and plasma cutter is rated for (higher torch pressure than what the table says).

If you need to, you can run a test line maybe 6" long, then move over 3" and run another test line but change one thing (like bump the amperage up 20) and see if it helps.

Personally, I think it matters if you are on 3 phase or 1 phase and if you have much voltage drop when pulling the given amps.

I've always guessed that the tables were set up in big factories with lots of 3 phase with little voltage drop - so the amperage is a little different if you are running single phase at whatever voltage you happen to have when the table is pulling however many amps. BUT I don't know that. I just know things work different with differnt power inputs.

Good luck! Arne

[adbuch]

Arne - thanks for your insight! Your tips about current setting and air pressure may be very helpful here. Those are some nice looking parts you have there. Keep up the good work.
David

[Pseudo]

Thank you all for your replies

If that's the case and your DRO shows the Z height when the THC Is on and making adjustments then cut a simple straight line on your stainless and read the DRO. When the cut is complete jog the Z axis down to the distance the DRO stated it was at when cutting and measure the torch height with feller gauges to confirm your DRO is in fact displaying the correct value. Hopefully it is and you can use your THC pot to get the torch down to that .020" cut height or whatever your chart says it should be.

Unfortunately I don't think I have a way to jog the Z axis, the software on the computer doesn't ask for a single setting related to height, and the THC block the torch height when I turn the manual mode on, I've looked into every document or manual we have that could mention this particular issue, but I got nothing...

[Pseudo]

We cut 304 stainless and 316 stainless using dry filtered air (no special gas) and it looks about the same as mild steel.

Just fyi.

If I'm having trouble, I go to a 60 amp table in the book for the plasma cutter and dial the plasma cutter up to 80 amps (but use the 60 amp table and 60 amp consumables). And then I open the air to the highest pressure the torch and plasma cutter is rated for (higher torch pressure than what the table says).

If you need to, you can run a test line maybe 6" long, then move over 3" and run another test line but change one thing (like bump the amperage up 20) and see if it helps.

Personally, I think it matters if you are on 3 phase or 1 phase and if you have much voltage drop when pulling the given amps.

I've always guessed that the tables were set up in big factories with lots of 3 phase with little voltage drop - so the amperage is a little different if you are running single phase at whatever voltage you happen to have when the table is pulling however many amps. BUT I don't know that. I just know things work different with differnt power inputs.

Good luck! Arne

We still need to install a gauge at our plasma's air input but once that's done I'll try this out!

[adbuch]

I very much agree! You most definitely need an inline pressure gauge directly at the entrance to your plasma cutter. Please keep us informed.
David

[FabLab]

At work (a Torchmate table) we have found that running a closer cut height helps a lot.. We typically run about 50% closer on stainless vs mild steel