cnc plasma table using ohmic touch

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A couple of years ago I installed a laser sensor that was suppose to detect the material height and set the pierce height without touching the material. Worked well on shiny material like galvanized sheet but didn't work reliably on anything with mill scale. Definitely didn't work on rusty plate. The laser was protected by a shutter that sometimes failed to open because of slag and grit. In the end I reverted back to the pressure touch method.Last week I was poking around my vendor's website and discovered they now support an ohmic touch method. This is a sensor that come down unto the material and then sets the height on the retraction. Called them up, explained my situation and frustration, and they sold me an ohmic system at a generous discount. I needed to re-new my support subscription in order to get the latest software that supports ohmic sensing.After I ordered the system I did some research to make sure my Thermal Dynamics SL100 machine torch had everything it needed. As it turns out I needed to upgrade to a shielded torch. I had to order the ohmic clip, shield cap and shield cup. As it turns out I should have been using shielded stuff all along.Today everything arrived and I installed it on the machine. Only gotcha was the tight space allowed for the screws... note the custom hex wrench (not provided in the kit). Haven't tried it yet... still need to install the software. Maybe the photos will help someone. Anyone use ohmic touch? Attached ImagesLast edited by forhire; 10-26-2010 at 07:23 PM.
Reply:Upgraded the software. Reprogrammed a MILLION settings because nothing transferred automatically.  Now the THC is going CRAZY  Starts out fine and then the THC delay expires and the torch lifts off and the voltage goes high. E-stop the program and the torch is like 3/4" off the plate! Switched back to the old software and it appears ok... so it's not a consumable issue. Must have missed something in the setup. Guess I'll be on the phone with tech support in the morning. On a good note... if I turn off the THC it cuts fine. The ohmic sensor appears to be working. I like the new shielded torch. Cutting very clean.
Reply:Called the vendor this morning. I had a setting wring in the settings. Everything is working perfectly
Reply:Ohmic contact is the most accurate initial height sensing method. It was first introduced by Hypertherm on its industrial height controls about 18 years ago. On the Hypertherm THC systems ohmic contact is also used during the cut to sense plate contact (collision).....in the event of contact during the cut, the torch will retract back to the programmed cut height rapidly, avoiding a colision and saving the part.Hypertherm also invented the shield technology on a plasma torch, however the patent has since expired, so it is available on some other brands! The PlasmaCam DHC2 and Samson cutting machines all use ohmic contact as well.A drawback with ohmic.....if water is on top of the plate it will often sense the water, or if the plate is primed or rusty, it will not sense. Most THC systems have a back up collision sense if the ohmic contact malfunctions.Good addition to your machine!Jim Colt
Reply:Hrmmm I have a shield cup for my torch but I never use it on my table.  Should I switch?  Machine is a Thermal Dyn 101.  The machine torch came with a nice shield cup but for some reason i switched to the standard cup.
Reply:Originally Posted by Jeep07Hrmmm I have a shield cup for my torch but I never use it on my table.  Should I switch?  Machine is a Thermal Dyn 101.  The machine torch came with a nice shield cup but for some reason i switched to the standard cup.
Reply:I guess you doing commercial stuff? Setting up an Esab right now.
Reply:This message is forhire, read your thread great what was your source for purchasing ohmic touch? could really use one! Thanks have a great one...Manny
Reply:Originally Posted by MannyBThis message is forhire, read your thread great what was your source for purchasing ohmic touch? could really use one! Thanks have a great one...Manny
Reply:Hello Forhire, just caught this thread and noticed the mention of the Ohmic touch. We recently purchased a Plasma Cam system with the Ohmic feature. In our case we have a Hypertherm 85 and found out that Hypertherm has a very nice addition to allow for "plugging" in this feature, it's a #220953 retaining cap with the plug-in clip as part of the unit. In the pictures that I have included it is the unit on the right, the other one is the stock item. Don't mean to hyjack your thread it's just that Plasma Cam didn't readily have this known as a need for their system and I thought that others might like to know about this. Best regards, Allan Attached Imagesaevald
Reply:Have you ever thought about cutting with a torch? I don't know how thick your cutting but it is actually straighter then plasma which is an issue for thicker stuff:
Reply:Originally Posted by gow589Have you ever thought about cutting with a torch?
Reply:You da manI see more T-Rex's!!!!!!!!!!Dave ReberWadsworth Ohio
Reply:Originally Posted by forhireThe ohmic touch is mostly for thin material that tends to flex and give a false z. Honestly I rarely use it as most of my cutting is in the 0.25 to 1 inch range. But for the occasional thin gauge it's a life saver.  I have a torch kit for my table but I haven't gotten around to setting it up. The plasma  does ok up to an inch... although the torch would definitely give a straighter cut. I have some inch work coming up so maybe I'll setup the torch (oxy-propane).
Reply:Originally Posted by gow589I am simply amazed at what the torch does every time we do it:
Reply:One issue with the torch is it really hardens the edge. Not a big deal unless you have to machine it afterwards. It's easy to bring the water table up to cool the part so it can be handled but we try to if it will have any machining done. It doesn't seem to help much but it seems like the right thing to do.Does yours have a water table?
Reply:Originally Posted by gow589Does yours have a water table?
Reply:Can you convert it to water?
Reply:Originally Posted by gow589Can you convert it to water?
Reply:Ours has and air chamber but it uses an enormous amount of air to move it up or down; but it does do it quickly. I think it was 1100+ gallons of water. I don't know how well the air works but the water is nice not only for taking the smoke but for cooling the part. I was thinking a 55gal drum or 2 could be used to convert a smaller table.
Reply:UPDATE: I finally was at my wits end with the ohmic touch not working reliably or at all. I called the vendor and diagnosed that the ohmic board was defective. Turns out I had one of the first boards and they were problematic. The new board arrived last week (free of charge) and I installed it a few days ago. Still couldn't get it to work right. Called tech support and they had me upgraded my control software to the latest version... and now it works perfectly every time. I'm so happy... my ohmic touch is working.