Material Contact Sensing Failure

[Complete_Loser]

PlasmaCam DHC2, 16ga hot rolled.
Torch has a material contact sensor added on (the ole hose clamp method).

It has worked great. Some times slag/dross will build up on the sensor ring and cause some gaffs, but we just clean it and go.

But last night i was cutting some of those guns from customdxf (awesome by the way!) and i cut out the first with no problem. Then the second one i had a "material contact sensing failure". So i did the usual, i wiped the metal off and cleaned the tip and sensor. Worked fine.
Then got the the third gun, and had a "m,c,s,f" for every pierce. Eventually now, i cannot get it to pierce. I get the failure alert every time. So i raise the Z. Sand the sensor (no slag there), and i even sanded the metal sheet. Then i hit cut, and STILL get the contact failure alert.

But i sanded and cleaned that sensor like crazy. Still no dice. So i moved it around. Tried raising and lowering. Still no dice.

This was about 1am. So I was about to give up, and the torch had sat for about 10min while i was doing something else. I decided to try one more time. So i hit "cut" and it resumed to cut the next element. A small .25" hole. And it went wacky on that cut. It went down, pierced and raised up to eventually an inch will cutting. WTF?
So i selected the next element, and again, "Material Contact sensing failure" alerts. So i gave up.

Any thoughts?

[CPK_Jim]

Did you try rebooting your computer? Ive had "strange" issues with my machine on occasion, I reboot the computer (which I normally leave run 24-7) and the issues go away.

Jim

[mdwalker]

When you clean the nozzle off are you taking it apart and cleaning inside the shield and nozzle? I have had instances where a small piece of metal almost too small to see will get inside the shield and ground out against the nozzle causing a contact failure. Also check your shield to be sure the bottom of it hasn't been deformed by striking the material. Sometimes they will get out of round from material strikes. Be sure and unplug the sensor wire and clean that contact also. You say you are using a sensor ring with a hose clamp? I tried that early on but kept having problems with it hanging up on tip ups and building up slag. I made one that doesn't use a ring but instead uses the shield itself. I will try to post pictures of how I made mine and maybe it will help. I'm using Hypertherm Powermax 1000 but it should work on others too.

Danny

[Complete_Loser]

Thanks for all the suggestions.
Tried them all. Rebooted this mornin and still had the problem. So we went to another configuration and now its working.

The config it was on cut height was set at .01. And worked for several projects until the problems.
Now this mornin, changed to .023 and works.

Oh well.

Danny, post up pics when you can. Would like to see what you have done.

[jimcolt]

You don't mention what plasma system/torch. If it is a shielded torch, such as a Hypertherm, then remove the consumables and clean the blowback material that is likely in between the nozzle and the shield......a small piece of the material you are cutting can blow in between these parts...shorting the shiled to the nozzle...and gan give this false reading. If you unplug the ohmic wire from your sensor......does the problem go away?

Jim Colt

[Complete_Loser]

Its not shielded. Thats why we are using the ohmic sensor.
Tried the wire. No luck.

Took the cap, nozzle, and electrode off, cleaned everything. Still had no luck.

Only thing that fixed was changing the cut height from .001 to .002.

[mdwalker]

I finally got around to getting pictures of the ohmic sensor connection that I use on my plasma. Cost less than a dollar versus $25 - $30 for the ohmic sensing cap. I use a hypertherm powermax 1000 but this should work for others. Parts needed: 1 hose clamp to fit the cap on your torch, 1 female electrical connector.

[jimcolt]

Sure looks like a Hypertherm torch in the picture! Maybe its a Miller, made by Hypertherm?

Jim

[mdwalker]

Sure looks like a Hypertherm torch in the picture! Maybe its a Miller, made by Hypertherm?

Jim

"

I finally got around to getting pictures of the ohmic sensor connection that I use on my plasma. Cost less than a dollar versus $25 - $30 for the ohmic sensing cap. I use a hypertherm powermax 1000 but this should work for others. Parts needed: 1 hose clamp to fit the cap on your torch, 1 female electrical connector.