Hello, i'm brand new here so bear with me!  We've been running plasma on our machine for some time now and recently added oxyfuel and a few strange things have been happening.  When in the middle of a part the machine will just go off on a tangent.  The display shows the parts properly and it continues to track the toolpath accuratly (off into the middle of nowhere).   The code shows nothing for a movement in that direction but somehow it just ghosts away in a straight line (cutting at the same feedrate as programmed).  These were on fairly large 1" and 1.5" pieces so it would be nice to quit damaging them!  It only does this when using the oxyfuel setup, never has on plasma.  Heres all that I change in mach to use the oxyfuel setup. 
Under ports/pins - mill options I check the "allow thc up down movement when not in THC mode" box.  Then under Input Signals I check the EMULATED THC UP and Down boxes.    I was told I had to do that to adjust height of the torch while the program is running. 

What do you guys think could be goofed up.  Some smaller parts are cut fine without issues.  On the latest larger ones it did it in the same place on two identical parts but have no idea why!!!   I then just go back to the start of where it ghosted and it completes the part just fine...

Thanks in advance!
Scott

If the only difference is the torch, chances are that you still have an electronic noise problem. This is hard to understand, because this seemingly electrically harmless change can cause problems. If you have an electrically operated torch control, it may be causing interference with one of the motor drivers, and causing it to generate phantom pulses that move the torch away from the intended path. The proof of phantom pulses is that they will cause the torch X&Y position to not return to your 0,0 reference point when you do a home. I recommend that you make sure that your cables are properly shielded and grounded.

Ok Thanks! I do have the solenoids for the torch grounded to the machines gantry right now.  I'll run a dedicated wire for them that doesnt ground to the table and let you know how that goes.  Thanks much for the reply. 

Well I isolated the ground from the table now but it still continues to do it.  It did it on 3 consecutive parts at the exact same point and was heading in the same direction.  It actually is making a large arc.  Here is a picture of it running off into the middle of nowhere.  THANKS!
I just upgraded to the latest version of Mach hoping that may solve it but it didnt.  Thanks.

It was not losing position either. Can you tell by looking at the picture of the code if it was something wrong with that? Thanks much

Ended up having to have the THC button turned off while cutting otherwise i needed to have the emulated thc up/down boxes unchecked but then I couldnt control Z axis while running the program.  So just to recap it ended up not having anything to do with the torch solenoids being grounded to the table.