Tomahawk 1000 OHMIC SENSOR

[RivetsNleaves]

I hope I’m in the right section to post this. If not Mods please feel free to move it to its proper section.

Dilema: can’t find ohmic sensor for my plasma.
Solution: DIY ohmic sensor
Questions: Am I touching the right part of the torch to sense material? Would touching “A” on the diagram be an issue to the electronics? Or should I go with the set up circled “B”?

Attached are the DIY ring I made photos.

[djreiswig]

Looks good. You want to use the lowest part of the torch to sense. Then you will need to program the controller to raise the torch to the correct height of of the material.
The item you have marked B is the gouging consumables. You wouldn't want to use those for cnc cutting.

[adbuch]

Here is what the consumables look like for my Hypertherm 85. When the shield is threaded on to the ohmic cap, the edge of the shield slides up under the copper lug. The ohmic sensing wire is attached to the other lug on the ohmic cap. So my ohmic sensing wire is in contact with the shield, and not the nozzle.



David

Hypertherm ohmic sensing consumables.jpg

[adbuch]

Jim Colt ohmic sensing.jpg

[RivetsNleaves]

The dilemma with this tomahawk1000's lc65 and lc65m torch is that the standard cutting "A" (in the diagram) is a ceramic shield. I called lincoln and they do not have a copper shield available for this unit which is weird because it comes with the cnc interface cable and a trigger wiring all ready for cnc cutting. I am touching the cutting "nozzle" which I think its not right the way I have built my DIY clip. Unfortunately I may have to make a copper sleeve that will be a hair longer/lower than the nozzle height and adjust my cutting height based on the difference between the nozzle and longer touching copper "leg" that will touch material.

There is no Copper shield (in "A" configureation) like all the other torches out there. In the "B" configuration the shield is copper but its for gouging thus will not work with my set up.

[adbuch]

Unfortunately I may have to make a copper sleeve that will be a hair longer/lower than the nozzle height and adjust my cutting height based on the difference between the nozzle and longer touching copper "leg" that will touch material.

bend it down.jpg

[acourtjester]

Here is my 2 cent worth. I do not think you should be touching the nozzle part of your torch as that may be in the plasma circuit. An Ohmic sensor should be a separate circuit not part of the plasma voltage path. On the Hypertherm torch there is a shield that is used for the Ohmic sensor circuit and it Does not touch the nozzle but is separate from it. This is the retaining cap (insulator) part where the wire is attached, and is shielded because it does not touch the nozzle. Attached is a DIY way of having a Ohmic sensor for a torch like yours. He used 2 copper wires attached to the torch in a way they are not part of the torch voltage path, and are separate. His setup shows the wires are arranged so they have a slight springy action when they touch the metal surface for the Ohmic contact. Now this is a separate circuit to the controller's input and requires a different Post Processor that has the commands in the G-code to look for the Ohmic sensor signal. This signal is a contact between the Ohmic contact and the metal surface acting like a switch to the controller. I will give info one a module I use for the circuit for Ohmic sensor you can buy from Amazon cheap and easy to hook up.
https://drive.google.com/drive/folders/ ... sp=sharing

Ohmic contact.zip

[tcaudle]

It appears the "gouge shield : is the Drag shield with the standoff crown removed . You cannot use the nozzle as the sensor . Its an active part of the arc start and the arc for cutting. If it is too far from the material it WILL arc to the sensor wire.

The shield is supposed to not touch the electrode so it (in theory) is inert .
I would go with he gouge shield and there appears to be an ohmic clip on that barrel to contact the shield.
The only other possibility is to fashion the bracket so it does not touch the nozzle but is a tiny distance below it

There is of course plan "C" and that is to mount he torch in a floating holder with a sensor / Switch and just lest it push the torch up to do the IHS and program in the offset in the software. Lots of people don't have Ohmic . Its better for thin material to avoid the torch weight from distorting the material but you can add counter balance springs to the floating holder that make the torch weight a lot less. Ohmic sensor are great until they miss or false then you better have a backup option or things tend to break The mechanical method is more reliable especially if you cut dirty or rusted metal.