I just upgraded to version 3.6 and added an ohmic touch sensor. I was cutting a bunch of parts and it would set the torch height too high to start now and again. This would cause the plasma to fail to start. I finally turned off the sensor and went back to the pressure sensing.
Are there some software settings I might be missing? Sensitivity adjustment? I understand mill scale and rust will affect it. Any tips and tricks to making it work consistently?
I have been using the ohmic touch for a few months. I feel like it is an option that should become standard. I bought it after I had been using my Dynatorch for a short time, and really ordered it only because it was pretty inexpensive and I wanted to see what it did.
Anyhow, recently I was having an issue that sounds like what you are seeing. Often, my torch would never get all the way down to the sheet when it was trying to find it to make its pierce. It would come down to within 1/4-1/2" of the steel, then retract its set pierce height amount and try to pierce. I talked to the folks at Dynatorch without really coming to a conclusion as to what was causing it (a faulty board was suggested but they thought this was very unlikely, they thought a dirty shield was more likely). Then, I realized that my main plasma cord coming out of the cord carrier did not have much clearance over the z-axis motor and into the torch. So as the torch went down searching for the sheet, the cord got tight over the z-axis motor. Apparently, it never got to the ohmic sensing stage because it would reach its maximum downforce before it reached the sheet. Does this make sense? I had to give the cord a little more slack and give it a little higher arch coming out of the cord carrier.
This is an example of how it did not have much slack before:
And now that I added slack and more arch:
Not sure if that is your issue, but I do believe that it could be a common issue for those using and not using the ohmic sensing.