PlasmaC torch starting problem (Solved with help from the famous three)

Rod. If I put a G4P15 in the gcode between each cut then it works fine as the 15 sec delay is enough time for the air to stop purging and then that settles the arc voltage from hovering at 0-20 to Zero.
At the moment I am just doing pierce cuts only.

Re Tom . Can you please take some pictures of the plasma and post here, i can try to figure out where that potection is located.
Or since you already have resistors in series with THCAD, can you find a 0.1 uF bipolar capacitor rated at over 300V and wire it in parallel to the THCAD input. Beware that it may blow or smoke during pilot arc, or burn the resistors, so have some spare ones ready.

photos.app.goo.gl/jCpFLVbwGN57V52HA

Tom. The two pics next to the THC pic, you can see where I have connected the 1M resistor to each terminal for the THC.
these are connected tot the input of the THC

The last one is a VID just to show that the machine does cut

Tom these are the scopes with set at 300
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This is a cut OK line at 20mm long

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and another same. You can see the ripple at the end on the cut in sync with the arc-ok-out

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The is a fail with the air purging. the arc-ok-out wave starts immediately as soon as it starts.
The torch-on never moves
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Yes I will do it again in the morning all the others were set at about 80 this one was at 10V.
the arc-ok wave is only 1 V and the arc-volt ripple looks like 20V

Clive wrote:

Yes I will do it again in the morning all the others were set at about 80 this one was at 10V.
the arc-ok wave is only 1 V and the arc-volt ripple looks like 20V

Ok I set it to 60v but fail to get a proper plot
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cut ok 60V

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failed plot this is after the first cut with the air still purging

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Ok cut

So it seems the maximum voltage this plasma can generate is about 230 volts. That is the value of the arc displayed during the failed cuts.

My guess is that on arc establishment of subsequent cuts (with air flowing) is that the blowback mechanism in the torch is shorted together (eg in arc starting mode). Remember that a blow back style torch creates the initial arc inside the torch with a dead short and then transfers it to the material. So the transfer of the arc does not occur for some reason.

I think the only thing you can do is service the torch and replace every consumable becasue by now are probably in a sad state.
If that does not work, it is how this particular machine is.

As an aside, its good to see the ArcOK being established at the correct time now so don't change any settings!

From these plots of good cuts, I see that there is a step down in the cutting voltage. I assume this is when the THC is enabled. Your arc voltage in Plasmac is set too low. It should be set on the naturally ocurring cut volts. I always sample the torch voltage to avoid this. Make sure the THC on delay is long enough for the voltage to reach the flat "plateau" observed in the charts before sampling.

My guess is that on arc establishment of subsequent cuts (with air flowing) is that the blowback mechanism in the torch is shorted together (eg in arc starting mode). Remember that a blow back style torch creates the initial arc inside the torch with a dead short and then transfers it to the material. So the transfer of the arc does not occur for some reason.

I think the only thing you can do is service the torch and replace every consumable becasue by now are probably in a sad state.
If that does not work, it is how this particular machine is.

Rod. I don't think I have a blowback style of torch it is a pilot arc type I believe the blowback type has moving parts inside mine does not.

My torch is new this one:- parkertorchology.com/wp-content/uploads/2019/06/SCMP80R.pdf