Plasma CNC-Table questions

[MaikTheBike2]

Thanks for your help,

The Mesa-Cards arrived and the plasma works with PlasmaC.

Thats very good, but it seems to cut the metal at an angle and there is a lot of dross on the backside of the cut. Also the cut quality doesn't seem so good.
Do you think that I need to find better parameter ? Or is the combination of Thermal Dynamics torch with a hypertherm 1000G3 power source not so good ?

I have attached some pictures of a part. Dross was already remove with a hammer and a chisel.
The angle on this part is about 10°. (1mm angle on a 5mm sheet)

Thanks,
Maik

[robertspark]

https://www.google.com/url?sa=t&source= ... 2742072378

cut direction?

speed of cut?

torch square to table?

consumables?

check o-ring condition, apply a dab of silicone grease.

[acourtjester]

From the image of the cut your torch is not perpendicular to the metal surface, the question is are the angles on all 4 sides of the square. If only on 2 sides determine which direction of travel to determine the axis that the torch is leaning. If on all 4 side you have tilting in 2 directions.
Now as Robert said the consumables can cause similar problems this is due to the plasma stream is not perpendicular to the torch body. I do not know about the Thermal Dynamics torch but the Hypertherm has a nozzle and shield and their openings can be misshapen. there is also 2 "O" rings in the torch that can be leaking, or the swirl rings can be bad. The silicone grease is for the "O" rings so they don't get damaged when changing consumables, this is a High temp grease, I bought some from Hypertherm.

a tilte.JPG

[adbuch]

From your first 3 photos, it looks to me like your torch is not square to the work. That much angle on the cut is not normal. Lots of low speed dross on the backside could indicate that you are cutting too slow. What settings (amps, cut height, cut speed, air pressure) are you using?
David

[weldguy]

It looks to me as though your cut speed is too slow. To find the ideal cut speed draw a straight line 12" long and cut a few of them increasing the speed with each cut. Keep an eye on the sparks under the plate and once they start shooting off on a slight angle behind the cut direction that is a good speed, if they are shooting off in front of the cut your too slow.
It also looks to me as though you have a worn out nozzle, when nozzles are worn out the hole that emits the arc will no longer be round. This will cause the plasma stream to shoot off on an angle and you will see this angle on parallel side of your cut. To prove this you cut a square and note the sides with the angle cut, now loosen your retaining cap and rotate the nozzle 90 degrees and tighten the retaining cap and cut another square, you should notice the angle is now on the other 2 sides of the square. If you have any angle on all 4 sides of the square its not likely a worn nozzle but rather incorrect cut speed.

[MaikTheBike2]

Thanks for your help.

I tried to cut some more pieces, but haven't found the right settings yet.

While cutting another part I noticed, that the arc is comming at a very large angle out of the torch. I inspedted the torch and the nozzle was worn out (as weldguy said). The nozzle was almost new and had only cut 3-4 small parts.
Then I changed the nozzle (bought with electrode here: https://www.weldcut.de/ger_m_Plasmaschn ... 0-282.html), but after 2-3 cuts there was metal on the nozzle and the nozzle already looks broken (see pictures).

I tried to cut with slower speed (800 mm/min) with new nozzle, but there is a lot of dross.
I think its too slow, but when I cut faster (~2000 mm/min) the plasma-cutter penetrates the metal, but when the machine moves its only "goughing" and sparks fly everywhere. There is no penetration at 2000mm/min anymore (only at start). The Powermax 1000G3 is set to exactly 40A and I don't know if it makes sense to go higher amperage because consumables are rated for 40A max. Sheet thickness is 5mm.

I changed the cut hight from 1mm to 2mm because of the negative cut angle on the sheet (as mentioned in roberts PDF-file).

First Cut with new tip and electrode at slow speed ( 800mm/min I think) :


Here you can see the sparks fly:


( stopped the machine because the cut didn't go trough)


Result: no penetration when cutting at 40A:



To sum it up: I think I'm cutting to slow, but when I cut faster then it doesn't penetrate when cutting, sparks fly and the nozzle wears out.
This manual suggests a cutting speed of 1600mm/min and 2500mm/min max: https://www.hypertherm.com/Download?fil ... &zip=False

[MaikTheBike2]

This is how I assembled the torch:

[acourtjester]

First with your nozzles burning up fast that can be caused by 2 things, incorrect pierce height and bad air supply. By bad air supply I mean oil in the air, the image with the tip straight up it looks like debris up the tip more than normal (may be common for that brand no sure). And the 2 nozzles in you hand. A side note you floating head switch seems to be moving as the torch moves down, maybe it is giving you an incorrect reading the when you tested it. The pierce height looks ok but the cut height looks a little high, 1.5 may be better. You have auto volts selected and also you entered values in the menu. I am just getting into LinuxCNC so I'm not sure when dialing in a setup you should use auto volts yet (IMHO). When changing speed to correct for dross you jumped to much in speed try 50 mm steps (800 850 900).

[MaikTheBike2]

Thanks,

is the pierce-height of 4mm ok when cutting 5mm thick steel ?
The compressor I use is a oil-free compressor, but the air-hose connected has been used on a oil-compressor for some time. So I guess I should buy a new air-hose.

I put the Powermax 1000 on Air-Test and found out, that the torch is leaking air on the top of the shield cap (see Picture1).
Is this normal ? Is the shield Cap broken or is there a o-ring missing and can it affect the cut-quality ? (Picture 2)

[acourtjester]

that sure look like a place for an "O" ring, you want all the air to exit the torch were is was designed to exit. This forms the plasma stream which does the cutting. Is there a break down image in the manual it should show if there is an "O" ring there, here you go. You may want to get some silicone grease to lube the new "O" ring.
https://www.rapidwelding.com/files/SL60 ... Manual.pdf

amissing.JPG

[Rodw]

As you noted, there is an o ring missing.
I have one of these torches (SL100) and with clean air, I never have such cutting problems until the electrode is totally worn away.
I never have such buildup of crud inside the torch consumables.
If replacing the o ring does not fix your problems, its an air quality issue
If there has been that much oil in the lines, you have a real problem to cleanup.

[adbuch]

Thanks,

is the pierce-height of 4mm ok when cutting 5mm thick steel ?
The compressor I use is a oil-free compressor, but the air-hose connected has been used on a oil-compressor for some time. So I guess I should buy a new air-hose.

I put the Powermax 1000 on Air-Test and found out, that the torch is leaking air on the top of the shield cap (see Picture1).
Is this normal ? Is the shield Cap broken or is there a o-ring missing and can it affect the cut-quality ? (Picture 2)

I think you have found your problem! As AC showed with his attached torch diagram, there should be an O-ring in that groove.
David

[MaikTheBike2]

Hi,

its 3 years later and now I have time again to find out why the Plasma-Cutter doesn't really work very well.

I put in the O-Ring and there is still some air comming out on the top of the cap.
But maybe thats normal because there are air-vent-holes above the O-Ring ?

I tried to cut by hand, but after about ~1m of cut length the nozzle started to get bad again.

Maybe the reason is that I didn't use shielded cosumables ?
I used unshielded without stand-off-cut-guide.

There seems to be a Shield Cup with Mech/Drag-Shied or deflector shield cup availible in online-shops.
Would that improve the cutting quality and the usetime of the consumables ?



Maybe somebody can explain what the shield is good for and what a deflector is good for ?
There seems to be a 50A to 60A Shield cup. Can I use it for lower amperage as well for cutting thinner sheets of metal ?

Thanks

[weldguy]

Are you dragging or touching the nozzle/tip on the material because that will destroy your nozzle very quickly. You want to be sure you have some distance between the nozzle and the material which is what the drag shield cap will give you.

[Rodw]

My guess is you don't have dry air. I never had issues with cut quality after fitting a refrigerated drier with the same torch!

[weldguy]

I second the dry air. That would have been my go to here but it sounded like you were dragging the nozzle on the material which will certainly be a problem. Both good things to remedy.

[MaikTheBike2]

Thanks for your answers.
I tried to drag the tip on the material because I saw the technique in this video:



It seems that there are two different tips for drag-cutting and above the sheet-cutting ?
All my cnc-and hand-tests were made with the "above the sheet"-tips with 40A or 60A.

Today I tried looked at the tip that I used for the hand-cutting test, which didn't look very nice after cutting 1m of steel and ignited the pilot arc. When the pilot-arc is burning it seems like the pilot-arc changes a little bit sometimes (brighter for a split second) and the nozzle is getting worse without even touching the metal. Maybe thats because I touched the metal with the tip ? Or maybe its because of bad air ?

Is there a way to test if the air isn't very good ? I tried two different compressors and the previous owner had the same problem with the machine (no straight cuts). So he also tried his own air-compressor...

I use a filter like this in my air-lines:



And there is no additional filter at the machine, although I saw a filter in the hypertherm manual. But the plasma was sold without fiter.