Plasma Cut Holes are Beveled

[arnegrant]

Marking and drilling works too but I like to let the table do the work while I weld.

Got to get two things done at once to make money in a shop.

[adbuch]

Arne - these are some very good tips and suggestions! Thanks for your input and hopefully your insight will help to guide the OP to achieve better results.
David

[Retro]

I finally tried the torch. Seems to do ok. But my parameters on 3mm steel are shit. Never got 100% good parts out of it. Always welded up areas during the cut. It sucks. Then the torch dives down on into the material so i drags the whole plate of steel on the table.
I ran this part on 2200 mm/min and corrected it already down to 1900. Maybe this works out. I already did one with 2750 and it was awful. The 2200 came atleast apart from the sheet und the torch didn't dive in.

And no, i can't turn up the amps a little, i only got 3 choices: 25, 40 and 60 Amps. And the 60 Amps should cut through 20 mm steel.

[weldguy]

Of the 3 amp selections you have what amperage did you select for these cuts 20, 40, or 60?

[Retro]

I used 40 Amps.

[weldguy]

40 amps is what I would have selected as well. It looks to me as though you are traveling too slow, lots of dross, cuts filling in behind itself, etc. For comparison a older Powermax 45 would cut that at around 129 inches per min or 3276 mm per min. Low air pressure could also play a contributing factor to this issue.

[Retro]

I set it to 5 bar as the instruction says. Not more than that its said. I'm not sure if its really filling behind itself. More likely cut not the whole way through.

[TJS]

5 bar is only 72psi. Seems low imho. I run my hypertherm at 110psi at the unit about 8bar, never dropping below 100psi when cutting.
What is your cut height. It should be around .060 or 1.52mm.
Is the torch dragging because you have a torch height control on. Can you turn that off for now to get your cuts and dross to where they are acceptable. Then play with the THC.

[Retro]

The initial cut height is around 1 mm. As Kjellberg states the voltage should be around 80 to 100 volts at 1mm. In this case 100 volts was kissing the sheet. I cant turn off the THC otherwise PlanetCNC sees a failure and wont continue.

Pierce height is around 3 to 4 mm.

The torch uses 50 liter per Minute at 5 bar.

[weldguy]

I am with TJS, turn THC off until you can get acceptable cuts without it. If you can't turn THC off this could get frustrating for you as THC will not function properly if it is not cutting properly. If there is no back door way to turn THC off and still cut then continue to increase arc voltage 5-10 on some straight line test cuts in an effort to stabilize it at an acceptable cut height. Not sure what model Hypertherm TJS uses but newer models will adjust the air pressure down internally and I suspect yours does not so feeding it more pressure than required won't be a good idea. If it says feed it 5 bar your doing the right thing feeding it 5 bar however I must ask where you are reading that pressure. I would want to see that 5 bar on a gauge installed at the air inlet of the plasma cutter. If you read that upstream you won't be accounting for pressure loss through lines, filters, etc. Also you want to see that 5 bar on the gauge when the air is flowing through the torch not when sitting idle.

[Retro]

I use 2 Pressure Gauges in line. One before the filters to bring the 1 MPa to 0,6 MPa and another one on the inlet of the plasma to bring it down to 0,5 MPa.

[weldguy]

OK well all I can suggest is find a way to turn THC off so you can do some straight line cuts so you can get a consistent and accurate cut height and then do some straight line cuts to determine the best speed at 40 amps. It may require a real redneck method of accomplishing that, for example, power down and disconnect the z axis motor, power back up and manually fix the torch height with a clamp of some kind so you can still feed the THC the voltage it wants but the Z axis cannot respond. I am not saying that exact scenario will work with your equipment, I am saying you need to get creative like that at this point so you can fix the number one issue of determining if you can cut a good clean line and getting some base settings that work so you can move on to the THC issue.

[acourtjester]

In your third image above looking at the edge of the tree the pattern shows what looks like to fast cutting speed. Another thing pressure gauges are great but you cannot really tell how much air is coming out the torch end while cutting. Long time ago some plasma manufactures would supply a type of flow meter to attach at the nozzle end of the torch, similar to the tube and ball on a tig regulator. If the solenoid in the machine or some sort of a blockage in the machine restricts the air flow you not going to cut well. I see you replaced the torch was that with a new cable assemble or just the torch itself?? What if you have an air leak in the hose!!

[arnegrant]

Have someone who knows what they are doing come and help you get started.

Good luck, Arne

[adbuch]

I agree with Arne. Maybe you can find someone in your area with some experience and have them come to your shop for a few "hands on" tutorial sessions.
David

[Retro]

The whole torch with all cables are complete new, there shouldn't be an issue. I'll make a few test cuts.

I have a flowmeter for mig/tig torches, but i only goes to 20l/min.

[Retro]

Alright, did some testcuts on 3 mm steel and it seems the new torch needs more voltage than the old one for marking operations. Based on the test cuts i would go for 1900 mm/min but the 1825 look good too. The hole isn't perfectly round and that seems to be a mechanical issue since this doesn't happen further down the cutting bed. I need to go over it with a spring loaded tension system. Right now there is none tensioning.

Btw. im now at 120 volts for the THC and it looks good. No top dross at this point, 130 volts more dross on top and 110 is sometimes tipping up with the torch; the edge seems to be the squarest at 120.

Down here are some pics of the tests at 2000, 1900, 1825, 1750, 1600. 1600 looks the edge very dull and overheated. 2000 looks too fast 1825 and 1900 seems the sweetspot. Edge is somewhat shiny and sharp edges, good corners.

The parts are 50x50 with a 20 mm hole in it (so roughly 2x2 outside and 3/4 hole)
It starts with 1600 on the left:

[weldguy]

Glad the extra voltage helped to get your torch up higher. Still so much dross though! You can't speed that up without losing the cut?

[acourtjester]

I just spent a little time looking around the web, and there did not seem to be a users forum for your plasma manufacturer. The only questions noted were from here (you) and CNCZone. From their web site it seems they are a industrial plasma supplier. Could it be your getting as good as it gets cutting thinner metal then the unit is designed for. It seems you are doing testing as you should trying to find the best cutting procedures, and looking for positible problems in the unit.
https://kjellbergcutting.com/contour-cut.html

[Retro]

I could try to talk to one of their technicans about that. After all its a 35 year old machine which i shouldn't expect the same like the new machines.

[Retro]

So its Christmastime again and i wanted to join the Christmas sales and print some money. Yes, it somehow worked out. This picture shows a full used Kjellberg electrode. At least i think its full used, it looks like.

These are the last ones available currently - i cut some more but they're already sold (thankfully). But there is still some issue with the dross. Its often hard to come by.

And i managed to destroy my Initial Height Sensing by some chrashes. I need to improve this system.

[acourtjester]

In the image of the electrode it seems that there is some metal particles on the tip. If so it may though the Pierce height off. You may be getting dross stuck on the tip.

[adbuch]

Perhaps try some anti-spatter spray on the nozzle/electrode as well as the material you are cutting.
David

[Retro]

No, i dont think thats metal from the outside. I would say thats the electrode material itself. And i use some Anti Spatter on the nozzle but not the material. Next time i shall try it.

[weldguy]

I wouldn't put anything on the electrode that's for sure. Some even say to handle them similar to a halogen light bulb, don't want oils and contaminants on them. I would keep that stuff away from your torch components all together. Let them burn clean and it will be what it will be.