03-27-2011, 09:43 AM
I understand to to operate a "touch to start" plasma torch that Sheetcam has to be modified or some type of script has to be invoked for it to operate correctly. My torch is a Esab 550 handy plasma. The manual says that you have to be within .020 or touching the material to strike the arc and start cutting. What I will need to happen is the z axis drop until the home sensor trips, then raise back up until the torch is .020 above the work surface, strike the arc and then raise up to the cutting height. From that point, the THC takes over. If anyone knows about this please enlighten me to what i will need to do to make this setup happen.


03-27-2011, 03:05 PM
The bigger issue is with damaging the torch nozzle (tip) with a straight in pierce such as that. When cutting by hand it is easy to start on an edge, or to tip the torch so the blowback does not damage the nozzle orifice. One of the reasons that pilot arc torches are more succesful in machine uses is that they can start at the pierce height (much higher than cut height) whhich allows the blowback to mis the front of the torch.

With plasma...as soon as the nozzle orifice is nicked or cratered...the cut quality and cut speed diminishes. Often this happens during the first two or three starts when piercing too close.

So...normally a height control indexes down to locate the plate surface, retracts up to pierce height (usually 2 to 4 times the recommended cut height), pierces, then after pierce complete indexes down to the cut height.

On 1/4" plate (with a Hypertherm) typical pierce height is .18", typical cut height is .06". This provides the best cut quality (cut height) and consumable life (pierce height)

04-12-2011, 07:58 AM
Hi jimcolt
What is the difference between a Pilot start and frequency start ? Can a frequency start Plasma use in a CNC machine ?