External THC (mode 2) Ignore ARC OK at start for 1 sec

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17 Jan 2022 13:39 - 17 Jan 2022 14:28 #232117 by fernandosf
I have an external THC that have a setting called DELAY_ARC_OK
It's manual says:  "This parameter adjusts the delay of output activation after arc is started so that it is possible to stabilize the arc tension at start"

I have made some tests and have reached the minimum value of 0.3 seconds (less than that and I start to get "arc lost" messages)

The problem is I depend on lead-ins to avoid burning surrounding material (thin, like 1mm) at start, as the torch keeps still for 0.3 secs before THC send ARC_OK to LinuxCNC.

I have seen in the manual that there is a Gcode command for that (ignore ok), but it would imply waiting for the next line to reactivate it.

Is there a way to ignore Arc Ok for just 0.5 secs and then let LinuxCNC read that signal again normally ?

My goal is not to have lead-ins on some works where I can save both inner and outer parts. Right now, I get divots if I skip lead-ins, because of the waiting for the external Arc Ok signal.
 
Last edit: 17 Jan 2022 14:28 by fernandosf. Reason: My goal...

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17 Jan 2022 15:10 #232125 by tommylight
Seems a bit excesive for 1mm material, should be no delay at all.
Or am i missing something ?

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17 Jan 2022 16:34 #232134 by fernandosf
It should be no delay at all.

The delay (0.3s) is not based on the time to pierce thru material.

If I set the external THC to "no delay" I end up getting "arc lost" errors at start.

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18 Jan 2022 07:22 #232225 by rodw
So I take it that the THC is generated by your external THC?
If it needs 0.3 sec to sort out things at the start of cut on thin material, its clearly ineffective.
A plasma cutter with its own arcok should return it in a few milliseconds.
Consider making Tommy's hardware arcOK using a reed relay as discussed in the qtplasmac manual.
The following user(s) said Thank You: tommylight

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