Thc velocity low

I attach an image with my z-axis values.  

If you are sure the voltages are correct, you could try increasing the P value in the THC settings area of the config tab from 10 to 20.  

The acceleration (750 mm/s^2) and 1200 mm/m  velocity
should allow ~0.5 mm minimum radius so that is not likely
the limiting factor.

(750 rather than 1500 mm/s^2 because only 1/2 the full acceleration is available to the THC)

Thanks for you explicatiion, Can the PID values ​​that I have in the joints affect something? In P I have 1000. 

No, the stepgen PID values are correct.

The physical meaning of a P term of 1000
at a 1 ms servo thread rate is that any
stepgen accumulated position errors
are corrected at the next waypoint
(1 ms later)

The first cut is at a speed of 300mm / min and it was successfully made, the second is at 1200mm / min and it is not finished since the height control does not respond very quickly. . 

The only thing I see is that plasmac.thc-feed-rate is 6000mm/min but the MAX_VEL in the joint is only 3000mm/min (50 x 60)

AXIS_Z MAX_VEL should be 100 (JOINT_# MAX_VEL * 2)

I don't know if that would cause an issue or not...

If the Z velocity and voltage were plotted in halscope,
that might give a clue to where the bottle-neck is.

Well guys after a night without sleep you see that the activation time of the thc was at 1.5s and it was too much for the slope of the metal that I wanted to cut and it did not allow to activate the thc I reduced it to 0.5 and it worked up to 2000 mm / min, thanks for his time I am still learning and calibrating my machine and reading a lot.

Yeah i forgot that PlasmaC had 1.5 seconds of delay on the THC, i wonder who's idea was that?
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Glad you figured it out.