Another Valid Arc Lost Post

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09 May 2020 06:14 #167101 by PurduePete
I am still pretty new to this particular software, so bare with me. I'm shifting over from Mach3.

I finally got my system up and running. Motion is pretty solid for the most part, little servo tuning still required but over all happy. I've got a Mesa 7i76e and THCAD-10. I've got the numbers in the config setup and it looks like the voltage being read is good. But I have an issue when I go to run a program. The arc does not read ok some of the time. Probably 3 out of 5 pierces it fails. And it sometimes doesn't even visibly strike the arc at all if the air is still on but still throw the error. My mode is set to 0, as I would like to use the arc voltage present as the arc ok signal as well. I have a reason for this! My Hypertherm 45xp is off my old table. It is an awesome cutter but has always had a delay in the arc coming on. This played havoc with my last machine. Was hoping that PlasmaC could compensate for the delay a bit better so that I could do better with thicker plate.

I've found a few posts and have compiled a list of things to try but thought it might be best to ask some questions.
Debounce
Would debounce setup on this signal potentially help? If so, could someone point me in the right direction to learn more about the right way to write this out?
Delay Timer
If there a timer that could be added to perhaps increase the amount of time the system looks for arc ok? Maybe increase it from .5s to 1s. I bring this one up because of a post I saw from Tommy about a timer of .5s being plenty. My machine actually seems to be closer to .6-.8s based on increases in pierce delays on my last machine.

Some other things I was going to try is setting the THC delay to .1 seconds. I saw this as a recommendation from Tommy as well.
It was suggested somewhere by rodw to bypass this issue by wiring the arc-ok signal, which I will do if required.
Check to make sure the system is up to date.


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09 May 2020 06:19 - 09 May 2020 06:23 #167102 by phillc54
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.
Last edit: 09 May 2020 06:23 by phillc54.

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09 May 2020 06:23 #167103 by PurduePete
I actually had the arc fail timeout set at 3.0s.

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09 May 2020 06:24 #167104 by phillc54

I actually had the arc fail timeout set at 3.0s.


I was too slow did you see my edit?

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09 May 2020 06:44 #167110 by rodw
Replied by rodw on topic Another Valid Arc Lost Post
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.

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09 May 2020 06:49 #167111 by phillc54

Just remember that if your plasma cutter decides the arc is lost, its going to cut the arc regardless of any synthesised arcOK signal

I would think that if a reasonable quality plasma cutter thought that the arc was lost it would ensure the arc was turned off.

Can you post a screenshot of your Config panel and your Run panel.

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09 May 2020 06:56 #167112 by rodw
Replied by rodw on topic Another Valid Arc Lost Post

Just remember that if your plasma cutter decides the arc is lost, its going to cut the arc regardless of any synthesised arcOK signal

I would think that if a reasonable quality plasma cutter thought that the arc was lost it would ensure the arc was turned off.

Can you post a screenshot of your Config panel and your Run panel.


Thats what I said, "cut the arc" ie turn it off.

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09 May 2020 06:57 #167114 by phillc54

Just remember that if your plasma cutter decides the arc is lost, its going to cut the arc regardless of any synthesised arcOK signal

I would think that if a reasonable quality plasma cutter thought that the arc was lost it would ensure the arc was turned off.

Can you post a screenshot of your Config panel and your Run panel.


Thats what I said, "cut the arc" ie turn it off.


So what is the issue then?

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09 May 2020 07:37 #167119 by rodw
Replied by rodw on topic Another Valid Arc Lost Post

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So what is the issue then?


You know my views on this. The plasma manufacturer provides a mechanism to tell the CNC controller the arc has been lost (and when a valid arc has been established). Where this signal exists, it makes no sense to bypass it. Surely there is no user on this forum who honestly thinks they know more than Hypertherm about Plasma cutting?

And yes, I know it takes a while to establish an arc on thick plate. My Thermal Dynamics takes quite a while on 16mm (5/8") to establish an arc too. But if you take off before that arc is properly established, why would you be surprised if the arc fails during the cut when it never got properly established in the first place?

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09 May 2020 07:49 #167120 by phillc54

You know my views on this.

Yes, I have seen them written often. :)


The plasma manufacturer provides a mechanism to tell the CNC controller the arc has been lost (and when a valid arc has been established). Where this signal exists, it makes no sense to bypass it. Surely there is no user on this forum who honestly thinks they know more than Hypertherm about Plasma cutting?

I don't know of any one here who does think like that but I also don't think that soft Arc OK is as much of an issue as you say.

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