Another Valid Arc Lost Post

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09 May 2020 08:16 #167124 by tommylight
I have used both methods, and they do work properly when set correctly, but i still prefer to use the hardware ARCOK, as can be noticed from the builds i do, i add that to most of the plasma cutters, be it with an reed contact or and inductor and some added electronics.
With software there are several issues to deal with to get it right, some plasma cutters will continue to output voltage in the range of 150 to 280V even after the torch is shut off since they have capacitors and that voltage will slowly fall back to 0 so for a split second when the torch is turned of the THC will start moving it down. Never really a big issue as it never reaches the material.
Some, especially inverter ones will have a 160 to 180V on the torch in cases where the pilot arc "missed" to transfer or did not strike an arc, so that will also cause the THC to synthesize the ARCOK signal and start moving torch down to lower the voltage while there is no arc or cutting going on.n Same thing happens on transformer plasma's but the voltage is much higher up to 280V, so the THC will move down rapidly and hit the material.
On my last build using THCAD i have the min arc voltage set to 80V and max at 150V to avoid any of those issues, and it works perfectly, never missed a single start.
The following user(s) said Thank You: rodw

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09 May 2020 13:47 #167145 by PurduePete

Check Arc Fail Timeout in the Config Panel

linuxcnc.org/docs/2.8/html/plasma/plasma...de.html#config-panel

THC Delay works identically for all modes.

EDIT: Set Arc OK High really high until you tune it in.


I missed the edit. Sorry about that. It was pretty late for me. I have the arc ok set as high as I can get it, 300v.

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09 May 2020 13:52 #167146 by PurduePete

Just remember that if your plasma cutter decides the arc is lost, its going to cut the arc regardless of any synthesised arcOK signal. NOt using your ArcOK signal is just adding one more potential failure point.

Its possible any relay you've used on your ArcOK circuit could be responsible for most of the latency. I've wired mine direct to a Mesa Input.

You could compensate for latency in ArcOK by reducing pierce dealy.


The arc usually does not establish at all. There have even been times that it doesnt strike at all, just the solenoid actuates to shut the air off and valid arc fail. Which is why I was thinking it might be a timer.

I can wire it directly to an input easily. I basically have no terminals or relays left in the panel anyway. Just to be clear, it isnt wired right now.

I dont think I know more than Hypertherm. Just kinda wanted to try something to improve my issue is all. Maybe it was silly. Itll be easy enough to throw that in there.

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09 May 2020 14:52 #167150 by tommylight
Can you still fire the torch manually ?
If yes, fire it and check if you get that error, it seems you have grounding / shielding issues.

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09 May 2020 19:12 #167164 by PurduePete
So I went ahead and wired up the arc ok but it is acting a little strange. The issue is 100% my fault. But I cant get the software to see my signal. I am wired to pin 30. When checking the hal meter it goes from false to positive when the torch fires. I added "net plasmac: arc-ok-in => hm2_7i76e.0.7i76.0.0.input-30 to my connections hal. The "plasmac: arc-ok-in" signal goes from false to true but I cant get the arc ok light to come on in the software. The mode has also been switched from 0 to 1. Kinda stumped on this one.

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09 May 2020 23:25 - 09 May 2020 23:27 #167187 by phillc54
The "plasmac: arc-ok-in" signal should normally be false.

Seems like you might need to use the in-not to invert the signal

EDIT: oops, I misread that.
Last edit: 09 May 2020 23:27 by phillc54.

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09 May 2020 23:28 #167189 by phillc54
Can you zip your config file and post it here.

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10 May 2020 03:34 #167229 by PurduePete

Can you zip your config file and post it here.


Here it is. You can see where I made notes in the connections hal so that it was clear what might be the problem when doing it. I am now getting arc ok to work. But it is still dropping out. My cut file (hello4) is attached as well. I am struggling when I get past the line with no offset. I've gotten the second circle to cut and that is it. It loses arc at the very end of the cut and then goes up to the top of the z travel and sits there with the error "valid arc lost program paused".

The cut file is just a random one to test some stuff that I use a lot in my work. Holes, lines and text and some round edges. Cut on my previous machine to check against this one.

Thank you for the help. I really appreciate how much you guys help everyone. I tried not to ask too much if possible.
Attachments:

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10 May 2020 04:13 #167232 by phillc54
Well the g-code you posted works fine in a sim config although you need to reverse the cut direction for better edges, just tick the reverse cut in SheetCam and leave it that way. The smaller holes should be cut with a reduced velocity.

Are you sure your cut parameters are OK eg cut height cut feed rate etc?

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10 May 2020 04:38 #167234 by PurduePete
That's a good point. I put sheetcam on the linux computer and havent pulled settings over or even messed with it much. Just enough to make a test file.

I had my z scale reversed so fixed that and it didnt change it. Tried without the THC and still get it. Was thinking the THC was lifting it or something.

It was suggested i try to redo my setup again. So I am going to do that in the morning. It is 1230 again.

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