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

More
19 Mar 2020 12:30 - 19 Mar 2020 12:30 #160741 by Clive S
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.
Last edit: 19 Mar 2020 12:30 by Clive S.

Please Log in or Create an account to join the conversation.

More
19 Mar 2020 12:40 - 19 Mar 2020 12:50 #160742 by Clive S

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
Last edit: 19 Mar 2020 12:50 by Clive S.
The following user(s) said Thank You: tommylight

Please Log in or Create an account to join the conversation.

More
19 Mar 2020 14:11 #160744 by tommylight
Cr@p !
Now on those pictures there is no spike flying off the screen, so all bets are off !
Now it is clearly visible that there is something causing the voltage between cuts to double and there is the noise on the second cut.
This should be easy to fix ( sorry Phill :) ), can the upper limit for arcok be raised to 300 ?
I think i already mentioned this, but the usual open circuit voltage for most plasma cutters is in the 260 to 280V, and some have that active as soon as the relay switches them on. This would just make it easier for cases such as this to continue using the generated arcok signal, without the need for installing current sensors inside the plasma.
That still does not fix the issue of the double voltage and noise in this case, that seems to be caused by the plasma source.
I have no explanation why that is occurring and it is very strange.
Clive, can you cut while the setp is at 900 or 1000 ? Try setting that at 300 and do several consecutive cuts.
The following user(s) said Thank You: Clive S

Please Log in or Create an account to join the conversation.

More
19 Mar 2020 17:47 #160757 by Clive S
Tom these are the scopes with set at 300
.
This is a cut OK line at 20mm long

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

.
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
.
Attachments:

Please Log in or Create an account to join the conversation.

More
19 Mar 2020 18:05 #160758 by tommylight
Can you please set the low arcok to at least 60V, and please do not lower it.

Please Log in or Create an account to join the conversation.

More
19 Mar 2020 18:17 #160762 by Clive S
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

Please Log in or Create an account to join the conversation.

More
19 Mar 2020 19:31 #160769 by Clive S

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
.
cut ok 60V

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

.
Ok cut
Attachments:

Please Log in or Create an account to join the conversation.

More
19 Mar 2020 21:51 #160777 by rodw
Replied by rodw on topic PlasmaC torch starting problem
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.

Please Log in or Create an account to join the conversation.

More
19 Mar 2020 22:40 #160781 by phillc54
From all these plots it seems to me that PlasmaC is doing what it should do.
My take is that the fails are reading the pilot arc and not the cutting arc.
It is interesting that the first cut is always good and the waveforms do show that.
From the plot below it looks to me like the voltage drops off before the arc ok and the torch on which would be correct behaviour on PlasmaC's part but it would be nice to confirm that with say a 1ms or 5ms division.
Warning: Spoiler!
Attachments:

Please Log in or Create an account to join the conversation.

More
19 Mar 2020 22:41 #160782 by Clive S

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

Please Log in or Create an account to join the conversation.

Moderators: snowgoer540
Time to create page: 0.188 seconds
Powered by Kunena Forum