Thc velocity low

ok thanks for your help, if really if the z axis moves how it should move but they are I am sure that if it should move 1mm it will move that distance, now you can help me where I look for information to update plasmac to the latest version and then of that I will prove the pid with 20 as you say.

This should do the trick:

linuxcnc.org/docs/2.8/html/plasma/plasma....html#update-plasmac

I upgraded to the latest version of Plasmac, I did tests at 300mm / min and the thc works fine, I raised the cutting speed to 1000mm / min and it no longer works very well on an inclined steel plate touch the torch and the reading of the the voltage seems to vary rapidly.

Kind of poking in the dark here, but here are some things that cant hurt to look at:

Have you confirmed the voltage readings with a known, isolated source, such as a 9v battery?

Have you verified that the axes move the commanded amount? For example if you tell Z to move 25mm have you verified it actually moves 25mm? (same with X and Y)

How angled is the piece of material you are trying to cut? Sometimes if the angle is too steep, the shield can touch the material inadvertently.

This is the 9v battery test well it actually has 7.5v but according to the calculations it is ok? Those values 

Check the battery with a multimeter and then verify the arc voltage displayed in plasmac matches