Valid arc lost & top limit is reached while THC moving up

Hello, I need some help here to have regular cuts in plasmac.

I am using debian 10 with a buster 2.8-rtpreempt buildbot, plasmac axis configuration v0.190, a mesa board 7I76E with THCAD-300 in a Hypertherm powermax 65.

1st Setup - Mode 0
THC voltage inside range. External arc voltage for Arc Voltage and Arc Ok.

Test: I've tried a lot of cuts with 2500mm long and in 10 tries i've  completed 1 and the rest stops in first 100mm with an error.

Result:  "Valid Arc lost error"

2nd Setup - Mode 1
Switch to mode 1 - External Arc Voltage for THC and  External Arc Ok from the same cutter connected to an input.

Result: Very similar, I have the same error "Valid arc lost"

3rd setup - Arc lost delay
After this try i used "setp plasmac.arc-lost-delay 2" in <machine>_connections.hal.

Trying the same test and getting similar results but the error is different. 
I've tried with delays of 5, 2, 1, 0.5 and 0.1.

Result: Got a little better between 100mm and 150mm but the goal is 2500mm. In 10 tries i've accomplished 1.
Sometimes cuts further but it's very difficult to reach a cut with 2500mm 
The error is always "top limit is reached while THC is  moving up".

In attachments I have .ini, .hal, .connections, config and run panel.
 
 
 
 
 
What should I try next? Is anything missing?

Thanks in advance

I think you should first check the cut height and feed rate, they seem a long way off what is in the Hypertherm cut charts.

I am using the charts from Hypertherm with the news consumibles.
I have adjusted the probe height and float travel.
Checked with different probe tests and THC movement is very accurate with the distances.

I'm with Phill, assuming that you are using the low speed finecut mild steel settings based on your cut speed, then your pierce height and cut height are not right.  Cut height is 1.5mm and pierce height is 3.8mm from the charts.

snowgoer540 wrote:

I'm with Phill, assuming that you are using the low speed finecut mild steel settings based on your cut speed, then your pierce height and cut height are not right.  Cut height is 1.5mm and pierce height is 3.8mm from the charts.

Cutting too high could explain the loss of a valid arc as the machine is unable to keep a stable cut environment when out of spec.
What is the actual voltage when you are cutting compared with the book value? If it is way higher this would help confirm this.

I am using Powermax65 with SYNC technology and the cut charts as follows and testing in Mild Steel 1.5mm.
 

What is the voltage when cutting?  I asked before.

Parameters Cut Volt at 94
Testing now I have mostly 89-90 Volts.
Max value 95
Min value 84

rodw wrote:

What is the voltage when cutting?  I asked before.
 

Parameters Cut Volt at 94
Testing now I have mostly 89-90 Volts.
Max value 95
Min value 84

Try this:
-set the THC scale so you get roughly 120V while cutting
-test
--
84V is to close to the lower limit of 60V, so that might trip the arcok.
-
You should disable AutoVolts while testing, after everything is working, enable it.