Cut rules and plasma volts

[4130metalworks]

Hi group, this is more an operation question than anything. Is it normal to need to manually increase the torch volts as the consumables wear so I don’t crash constantly? For this particular material (5mm mild steel) i start at 138volts and increase 1 or 2 volts for the next sheet and so on. I do monitor the cut height and it’s correct at 1.5mm and is giving an excellent cut. I have recently split up my sheetcam cut rules for holes, slots and outside just incase sheetcam was getting confused.

The cut volts hover around the 138 whilst cutting and only fluctuate +or - 1 volt maximum unless the thc is disabled for slow downs
Generally the torch crashes on longer runs but can happen sporadically
Masso g3 touch
Thermacut 75sd
Masso dthc
Myohmic pro sensor

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[djreiswig]

Torch volts is affected by electrode wear. As the electrode wears the arc gets longer, increasing the arc volts, causing the THC to lower.
I do find that I need to adjust my volts setting up slightly as the electrode wears to maintain the correct cut height.

[weldguy]

Perfectly normal as djreiswig stated above. I like to see guys in tune with their equipment like you obviously are

[4130metalworks]

Thanks for the replies djreiswig and weldguy, i am slowly learning the ropes. It’s definitely not as simple some make plasma cutting out to be

[Deezl Smoke]

So the torch crashes into the plate? That is not normal no matter the wear. I'm not at all familiar with your power supply, but I'd think a fault should show up and shut the torch off before it crashes. My Hypertherm PM throws a fault something like "consumables at end of life" or similar.
I doubt sheetcam is confused. What does your electrode look like where it sets against the nozzle?

[4130metalworks]

This is after 5 sheets of 5mm
Still cuts just fine, all I get is the occasional torch touching the work

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[Deezl Smoke]

I'll be curious what the experienced crew thinks, but I think that black ring around the hafnium shows a possible problem.

[tnbndr]

This is after 5 sheets of 5mm Still cuts just fine, all I get is the occasional torch touching the work

The number of sheets doesn't matter as much as the number of pierces. I had Mach 3 setup with a pierce counter and I knew that at around 1500 pierces my electrode would fail.
That electrode is at the end of its life IMHO, but 5 sheets of intricate cutting and pierces could possibly wear out an electrode.

[weldguy]

Correct, it's not normal to crash in to the plate, I was referring to it being normal to have to adjust your arc volts to maintain a specific torch to work distance as the electrode wears to prevent it from crashing into the plate. As for the black around the hafnium I suspect that is a carbon deposit from contamination in the air supply incinerating in the arc.

[4130metalworks]

I thought it was a bit odd to manually adjust voltage. Maybe the masso dthc isn’t doing its job

[weldguy]

Not odd at all, as the electrode wears the arc gets longer, when the arc gets longer the voltage increases, when the voltage increases your dthc see's the voltage is higher than you have set, the dthc then lowers the torch to get back to the target voltage, as a result your nozzle to work distance gets closer. Sounds like things are working pretty good.

[adbuch]

Not odd at all, as the electrode wears the arc gets longer, when the arc gets longer the voltage increases, when the voltage increases your dthc see's the voltage is higher than you have set, the dthc then lowers the torch to get back to the target voltage, as a result your nozzle to work distance gets closer. Sounds like things are working pretty good.

[Deezl Smoke]

Not odd at all, as the electrode wears the arc gets longer, when the arc gets longer the voltage increases, when the voltage increases your dthc see's the voltage is higher than you have set, the dthc then lowers the torch to get back to the target voltage, as a result your nozzle to work distance gets closer. Sounds like things are working pretty good.

I think cut height would be near .060" for 5mm or so would it not? I think that black ring about the hafnium is a sign of the issue causing the torch to hit the plate.?

[weldguy]

Not odd at all, as the electrode wears the arc gets longer, when the arc gets longer the voltage increases, when the voltage increases your dthc see's the voltage is higher than you have set, the dthc then lowers the torch to get back to the target voltage, as a result your nozzle to work distance gets closer. Sounds like things are working pretty good.

I think cut height would be near .060" for 5mm or so would it not? I think that black ring about the hafnium is a sign of the issue causing the torch to hit the plate.?

For sure, I would expect .060” for cut height and thought the same thing…thats a long way down, seems like more than electrode wear causing it hit the plate. Of course we dont know if the op actually measured to confirm its .060” or not. Many folks set it to .060” and assume thats what they get out on the table when in fact its not. Indeed the black could be air contamination and could certainly cause the torch to hit the plate. Hard to say for certain but i think this topic is helpful.

[4130metalworks]

Thanks for the reply weldguy, yes I do periodically measure it and also watch the torch to eyeball the height also

There will be something I am doing wrong, that's what time and experience I hope helps with

[weldguy]

Since you are confident the torch height was in fact .060" you would pretty much have to have a .060" deep divot in the electrode before the torch came into contact with the material. For this reason I believe Deezl Smoke could very well be correct that the torch crashing into the material has something to do with the black staining on your electrode. If you get a burp of moisture, compressor oil, etc through your plasma stream this will throw off the dthc and could cause the torch to dive into the material. What do you use for compressed air filtration? Often people do not have clean enough air.

[Deezl Smoke]

Since you are confident the torch height was in fact .060" you would pretty much have to have a .060" deep divot in the electrode before the torch came into contact with the material. For this reason I believe Deezl Smoke could very well be correct that the torch crashing into the material has something to do with the black staining on your electrode. If you get a burp of moisture, compressor oil, etc through your plasma stream this will throw off the dthc and could cause the torch to dive into the material. What do you use for compressed air filtration? Often people do not have clean enough air.

I've noticed from time to time when I get ****** and run cheap consumables, the electrode to nozzle fitment is suspect and that's when I get those soot marks, and, usually thc issues as well as that "sewing machine" cut. I think the Hypertherm electrode's spring quality is highly over looked and misunderstood. But that's Hypertherm stuff.

after faulty cut.jpg

[4130metalworks]

i have a dryer, smc water trap and 2 smc oil removal filters before the plasma. We also do spray painting so all lines need to be perfect.

Maybe the marks are from outside water splashing on the electrode, although when the table is completely dry i still have same issue. Because the thermacut plasma i am using is a copy of the hypertherm I could try their consumables to see if there is a difference

Thank you for everyones suggestions too

[4130metalworks]

I did check the air just in case, the white paper was spotless

[Deezl Smoke]

I did check the air just in case, the white paper was spotless

So was mine when I did that test.
DTHC has been some of my biggest issues with my table. It's not so much my equipment as it has been my ignorance as a beginner to cnc. The membership here has just been an incredible and priceless asset with their sharing of experience and knowledge, as has been Arclight Dynamics, the maker of my table.
For a while my torch would literally crash into the plate. Not just touch it, but dive into it and pull the torch from the magnet mount.
While diagnosing my issues, the folks here would mention so many points of possible failure, it was a real eye opener. My memory is not what it used to be, but I think even Jim Colt had a video or a post on this site about the plasma stream and what it takes to make a good one. So many things need to be just right to make a perfect plasma stream.

Since you mention your air system supplies other operations, and if I recall correctly, you mentioned your torch mainly hits the plate on longer runs, do you have a way to monitor your air pressure at the power supply while cutting?

I'm starting to wonder if your air pressure is dropping when the demand for extended run times is placed.
The other thing I learned from Arclight, is do not over pressurize the input to the power supply. I was figuring since there is a regulator in the power supply, I should just put full compressor capacity to it, which for my system is over 150psi. Arclight said to reduce that to no more than 120psi.
If the air pressure drops from specified needs, and your hafnium insert looks like it sort of creating an unconfined arc, then I can't help but wonder if that would cause a faulty plasma stream and that burnt soot ring might be the electrode and/or nozzle material being consumed at the point of mixing.
This is Hypertherm's tool setting on my Sheetcam toolset for .1875" steel.

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[Deezl Smoke]

This is how my electrode wears at 105amp.

hafnium.jpg

[4130metalworks]

I think you are onto something deezl smoke, my pressure does drop to 80 psi on longer runs and sits closer to 100 when the compressor has freshly refilled. That is according to the gauge built into the plasma

My compressor is more than enough ( 42cfm min output) so i will try adjusting the pressure switch to tighten up the on and off times

I see yours is only 68 psi, maybe mine is too high as well. We are quite different in cut speed but similar in voltage. Might bump my voltage up a bit and see what the cut quality is like

[4130metalworks]

Tried raising my air pressure, it now never dips below 90psi with plasma flowing. After having a range of odd issues yesterday I believe its emi that builds up after a while. The torch crashed twice, touch off didn’t work and the controller ran through the g code without firing the plasma

So i have started a fresh post hoping to get input from an electronic wiz

[adbuch]

Tried raising my air pressure, it now never dips below 90psi with plasma flowing. After having a range of odd issues yesterday I believe its emi that builds up after a while. The torch crashed twice, touch off didn’t work and the controller ran through the g code without firing the plasma

So i have started a fresh post hoping to get input from an electronic wiz

Why do you think it is EMI?
David

[4130metalworks]

Hi David, its only a theory at the moment and is going off someone else’s similar experience. My first sheet is always fine, it’s usually the 2nd that plays up. The idea is the emi builds up over time and releases, kind of like getting a shock when sliding your feet on the carpet