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Ohmic sensor working intermittently

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Joined: Wed Jun 17, 2015 6:57 pm

Ohmic sensor working intermittently

Postby Thor » Wed Jun 20, 2018 11:24 am

My ohmic sensor seems to not want to sense randomly, cant make 1 part without it estopping on the floating head switch.

I have a ground wire going from the floating head all back the the X axis head unit that has a main ground connection back down to the terminal bar in the main electrical cabinet (So I'm not just running ground through the linear rails but an actual wire connection). I have checked continuity between the fine cut shield cap and the tab where the wire hooks onto. I have cleaned the main ground clamp contacts and have it hooked right to the sheet. I have put new consumables and a new shield on, still faults out once or twice per part.

Cutting 24ga stainless sheetmetal with 2b finish.

When it has issues I can lower the torch down and rest it on the sheet and the light on sensor will not come on or sometimes will flash. Sometimes it works perfectly, other times it seems like a delayed sense and then the torch wont fire as it resting on the sheet yet when it should be up at pierce ht.

I'm at a loss for why its working intermittently.

Posts: 125
Joined: Wed Jun 17, 2015 6:57 pm

Re: Ohmic sensor working intermittently

Postby Thor » Wed Jun 20, 2018 11:41 am

Of Course I put all new consumables and shield in again and now it seems to be working fine. Only thing I could see is the end of electrode and the inside of nozzle had some black soot marks, maybe that was enough to mess it up

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Re: Ohmic sensor working intermittently

Postby Largemouthlou » Wed Jun 20, 2018 6:53 pm

The biggest problem I had was my wires were just a touch to short and the would wiggle loose just enough to give me a fit . I raised the torch a half inch to give extra slack and been 99 % perfect.. I cut aluminum, I still have the occasional flair up on initial pierce due to metal composition,, I keep a spare wire run from the ohmic collar to the side of machine. When I have an issue I restart the g code and use the wire to make contact and fool the sensor into working.. normally works well after that.. For some reason there is a spot here and there that dose not short out the sensor..
Last edited by Largemouthlou on Thu Jun 21, 2018 7:26 pm, edited 1 time in total.
1250 hypertherm
4 X 8 Precision Plasma
CandCnC electronics

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Re: Ohmic sensor working intermittently

Postby tcaudle » Thu Jun 21, 2018 11:53 am

There is a misunderstanding about connections on the Feather Touch. Its ll about the shield connection and the connection to the "plate" (material) If you use the table structure as one connection (doesn not matter if its grounded or not beacuse the Ohmic sensor is not referenced to ground) then that connect must be low resistance. the good news is the FT-01 is a "continuity " checker , You can literally go from the two contacts at the FT.01 mosule and use ti to check a conduction path. Shorting "TIP" and "PLATE" will light the light. A bad connection in either leg will NOT light the light.

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