[travmc1]

What is the extra wire I see going to the torch head and it is banded to it? I have see it on a few videos. Even Hypertherm has it on there Powermax brochure.

[Al_The_Man]

Just a guess.
Pilot Arc conductor/option?
Al.

[jimcolt]

It is called Ohmic contact....it is simply an electrical connection to the shield on the front of a shielded plasma torch.....it is used with some of the more accurate torch height control systems to find the surface of the plate (before the plasma starts) to ensure that pierce height is correct....to provide better consumable life.

This technology came from Hypertherm about 20+ years ago.....almost all industrial plasma's use this, the more advanced entry level air plasma systems that are mechanized use it.

You can see the wire connection in this picture...it connects to the torch retaining cap, which connects it to the shield. Tis pic is of a Hypertherm Powermax85 torch on a PlasmaCam machine (with a www.snapncut.com magnetic breakaway)...the PlasmaCam machines have the ohmic contact function built into their height control system.


Jim Colt

[travmc1]

Thanks Jim
I Just purchased a Hypertherm Powermax 85 (Just thought you like to know ) and I am using CandCNC DTHC II. I will have to ask Tom if there is a option like that on his systems.

[jimcolt]

There is not currently an option to use Ohmic on the CandCNC systems. Those systems use a "floating head" z axis with a limit switch that senses contact with the plate.....which works very well.

The advantage that ohmic has is on plate that is thin enough, or warped enough to deflect with the force of sensing (touching) the plate....if the plate deflects with a torque sensing or limit switch sensing mechanism...then your pierce height will be incorrect...and that can affect consumable parts life in the torch. The ohmic sensing uses a light touch...and even if the plate does deflect it does not start measuring the upward movement of the torch until it loses contact....for the most accurate pierce height positioning. Another real time advantage of the ohmic contact is that it can be used for collision protection during cutting...and can raise the z axis quickly if there is contact.

The drawback with ohmic is that it will sense water (water table applications) and if the plate is extremely rusty, dirty or painted...it will not sense at all. Most high end (expensive) industrial height controls use ohmic as their primary plate sense mechanism...with an automatic backup of z axis torque sensing (sensing an increase in motor torque when plate is contacted) if the ohmic does not sense.


Jim Colt

Thanks Jim
I Just purchased a Hypertherm Powermax 85 (Just thought you like to know ) and I am using CandCNC DTHC II. I will have to ask Tom if there is a option like that on his systems.