I've been battling an Ohmic problem for about a month. My Ohmic has 24v running through it, when it completed the circuit, it retracts as soon as it crosses the lower threshold of 23.5 volts. It would start at 0v and as soon as I made a cut, it would then go up fairly quickly. Shortly it would be above the lower threshold so it thought it was probing even if it wasn't touching the material. This voltage would slowly "bleed down" and get closer and closer to 0v as time went on. As soon as I would cut again, it would go right back up.
My hypertherm ohmic retaining cap isn't completely isolating the outside from the inside of the cap. I have literally spent the better part of 20 hours chasing my wiring down, trying to find shorts, etc. I had finally had it with trying to figure out why my voltage kept going up and staying past the threshold rather than dropping back to zero. I was giving up on it temporarily so that I could just get back to running the machine so I put the non Ohmic hypertherm retaining cap back on it and I was just going to use the float switch from here on out. When I did that I took the Ohmic wire and touched it to the shield to see if it would bring the voltage back up above 0volts. When I did that the voltage didn't flinch so I jogged it to the table and held it to the shield again and got a very stable 24v. I ziptied the Ohmic wire to the shield of it, and made some cuts and it's working exactly how it's supposed to for the first time! It goes back down to 0v after each cut rather than climbing with each cut to above the threshold and causing issues. I also think that this was giving me bad offsets with my cut height sometimes. I'm glad to at least think that I have it figured out for now, we will see as time goes on!
Has anyone else ever had this issue? I thought that maybe it was due to debris inside the retaining cap, but I didn't see anything.
Powermax 65 ohmic problem
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TrinityFabworks
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Rodw
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Re: Powermax 65 ohmic problem
Is it a water table? They are quite problematic with ohmic sensing and the Hypertherm seems to be worse than my Thermal Dynamics with water in the tip shorting to earth. We had to modify our Linuxcnc ohmic sensor circuit in both software and hardware to get reliable probing on water tables.
I have seen the circuit bleed to 0 if the mains power is switched on and off due to charge in the power supply capacitors.
Can you pulse the torch to get airflow happening? What does that do? Does it clear the fault to 0 volts?
I have seen the circuit bleed to 0 if the mains power is switched on and off due to charge in the power supply capacitors.
Can you pulse the torch to get airflow happening? What does that do? Does it clear the fault to 0 volts?
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TrinityFabworks
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Re: Powermax 65 ohmic problem
It is a water table, but I am using plasmac and hypersensing. (you will see my other post on the plasmac forum) It wasn't a problem with the circuit I don't believe. I think I've narrowed it down to the ohmic retaining cap having an issue.Rodw wrote: ↑Tue Oct 13, 2020 9:17 pm Is it a water table? They are quite problematic with ohmic sensing and the Hypertherm seems to be worse than my Thermal Dynamics with water in the tip shorting to earth. We had to modify our Linuxcnc ohmic sensor circuit in both software and hardware to get reliable probing on water tables.
I have seen the circuit bleed to 0 if the mains power is switched on and off due to charge in the power supply capacitors.
Can you pulse the torch to get airflow happening? What does that do? Does it clear the fault to 0 volts?
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Rodw
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Re: Powermax 65 ohmic problem
Yeh, I saw your post on another forum. It would probably be better posting on this section for plasmac. viewforum.php?f=203
I would check a probe event with halscope for both caps and see if there is a voltage change visible with the ohmic clip. If there is a slight step up in voltage on a probe, that would indicate to me that its likely to be a faulty cap. It would be interesting to know if snowgoer and some of the Hypertherm guys on Linuxcnc are using an ohmic cap. You'd expect they would be. Maybe ask the question back on the other forum.
I would check a probe event with halscope for both caps and see if there is a voltage change visible with the ohmic clip. If there is a slight step up in voltage on a probe, that would indicate to me that its likely to be a faulty cap. It would be interesting to know if snowgoer and some of the Hypertherm guys on Linuxcnc are using an ohmic cap. You'd expect they would be. Maybe ask the question back on the other forum.
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TrinityFabworks
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Re: Powermax 65 ohmic problem
I put it here because I've pretty much narrowed it down to my hypertherm. I put it on the Linux forum at first because I thought that it may have been my wiring. I figured I'd copy it over here to see if anyone else has ever had that issue with their hypertherm or to see if Jim Colt might respond.
