Ohmic no longer works

[DLE]

Table has been running great thanks to the support from torchmate. Suddenly however, my ohmic sensing has stopped working. No click of the relay, no indicator light in VMD software. Could the relay be bad? All wires are still terminated, and I can't find anything else that could be bad. Any ideas?

Thanks

 

[Matt]

Go to machine settings->Advanced tab, you should see a button that says Relay Off, toggle that button on and off and see if the relay is making a clicking noise

 

[LECS-Chad]

or remove the orange ohmic wires from the relay and wire nut them together. test ohmic by lowering the head to touch the material or ground. if you get indication of ohmic then possible that the relay might have went out.

 

[DLE]

Okay, it does click when I hit the relay off/on

 

[DLE]

The relay off/on makes the relay click, then I tied the two wires together, lowered torch and the indicator light does not illuminate when I lowered the torch to the material. any ideas?

 

[Dnmeistr-LECS]

In order for ohmic to work, there needs to be a clear path between the material sitting on the table to where the VFC box is gounded to the table. To check this, use a multimeter and check for Continuity between the material and where the ground wires is connected from the VFC box. To check if ohmic is functioning, jump the ohmic wire on the relay box to the ground stud on the VFC box, this will indicate ohmic is connected on the VMD software screen. If this works and you have verified continuity to the material then it should also work when you touch the orange wire on the machine torch to the material. Also ensure the ohmic clip is making good contact with the orange wire as well as the copper shield on the machine torch, again multimeter can be used for this. If ohmic starts detecting again be sure to separate the orange wires on the relay, do not fire the torch with the relay jumpered or the two orange wires connected to each other.

 

[cademaer]

This exact same thing was happening to me. To solve the issue I ran a wire from the 'star' ground lug to the plate I was cutting. The cable has a large alligator clip on it to attach to various plates. There should be a 12vdc voltage between the copper on the ohmic cap and the plate you are trying to cut. Take a multimeter and touch the positive (red) end to the ohmic cap on the plasma torch and touch the other (black) multimeter lead to the plate you are trying to cut, you should see 12vdc (or at least something close to that). If not, put the black test lead on your star ground. If you are still not getting any vdc measurements then you have at least eliminated a bad voltage pathway as a probable issue.

 

[Dnmeistr-LECS]

Yes forgot to mention that if you do not have continuity from the material to your Star Ground (where VFC box is grounded to), then run a jumper wire from Star Ground to your Material, and then you should have continuity.

 

[DLE]

So I've ran a jumper from the star ground to the material, touched the plate with the torch, no ohmic. The only time I can get an indication of ohmic is when I jumpered the orange wire to the star ground itself. Other than that I get no results, I get continuity everywhere else...

 

[Dnmeistr-LECS]

Good you have now determined the Ohmic circuit is working. Electricity follows the path of least resistance, we know this from Ohms Law. It could be that you have mill scale on your material or rust or dirt or what have you, think of a dirty battery terminal causing your car not to start. If that is the case then you have to turn Ohmic off, and tell the software where the top of material is, by doing this in the Job Setup menu.

A multimeter will tell all, touching from the material to your star ground, also ensure you have continuity from the bottom of your shield cup to the bare wire where the orange wire is crimped onto the spade connector.

 

[cademaer]

So, If you disconnect the orange wire from the ohmic cap on the torch and measure for a DC voltage between it (the tip of the orange wire) and the star ground, do you see any voltage?

 

[inkognito]

check you have 12vdc between the orange wire and gnd.
short the orange wire to gnd for 1 sec during which time the voltage will be 0vdc

 

[DLE]

Running a gator clamp from the star ground to the material got it working again, thanks for the help! Ive also noticed that periodically the relay output shuts off "by itself". Seems odd, but can certainly live with it.

Thanks!

 

[Dnmeistr-LECS]

This is by design, the relay is there to prevent any feedback from the plasma cutter, relay turns on automatically when lifter is activated and comes down to sense the material and turns off automatically when the ohmic circuit is completed. Good to hear you got it working.