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Ohmic sensing issue.

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engenironworks
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Location: Vanderhoof BC Canada

Ohmic sensing issue.

Post by engenironworks » Tue Apr 12, 2022 2:12 pm

Hi. New member here. Bought a Growth 4x4 table a couple years ago. Had nothing but grief with it. Struggled with customer support. Hoping I can get some direction here. I walked away from it in frustration. When it works it works well but when it doesn't... I'm back to try again. I'm new to the whole CNC thing. Learning as I go. It stopped in the middle of a cut and now it's not getting an ohmic signal. I googled the crap out of it and found some things to look at. This is where I'm at. Material on the table to star ground 0.5 ohms. Material to ground on VFC 6.2 ohms. Shield cap to relay 0.8 ohms. Turned relay on in advanced settings. I can hear it click and have continuity between the screws. With the relay forced on I get the ohmic sense light on the VMD screen. Another time it acted up I added a ground from the material to the star ground and it worked great. for awhile. Any help would be appreciated. Thanks.

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djreiswig
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Location: SE Nebraska

Re: Ohmic sensing issue.

Post by djreiswig » Tue Apr 12, 2022 9:51 pm

Ohmic is a like a continuity tester. The torch is one contact and the material is the other.
When I had issues with mine it was because I hooked the plate connection to gantry frame. The connection was good to the material when I checked it, but after a while it lost continuity. I finally ran a wire from the ohmic module to my water pan. I still occasionally have an issue, but it is much better. When i have an issue I just put a scrap on the material and touch it to a different place on the pan. Most likely slag is getting in the way so this takes care of it.
To troubleshoot, hook a wire to the tip connection and starting at the material work your way back to the plate connection until you get continuity. Where the circuit is broken is where your issue lies.
You could also use a wire from the module directly to the material. This would eliminate breaks in the circuit.
2014 Bulltear (StarLab) 4x8
C&CNC EtherCut
Mach3, SheetCam, Draftsight
Hypertherm PM65
Oxy/Acetylene Flame Torch
Pneumatic Plate Marker, Ohmic, 10 inch Rotary Chuck (in progress)

engenironworks
1/2 Star Member
1/2 Star Member
Posts: 3
Joined: Thu Mar 31, 2022 9:38 pm
Location: Vanderhoof BC Canada

Re: Ohmic sensing issue.

Post by engenironworks » Thu Apr 14, 2022 11:59 am

Hey thanks for the reply. Out of all the hiccups it's had this is the first time it's done this. I'm going out to mess with it. I'll try what you said and see where I end up. Thank you again.

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djreiswig
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Posts: 1438
Joined: Thu Nov 19, 2015 10:02 pm
Location: SE Nebraska

Re: Ohmic sensing issue.

Post by djreiswig » Thu Apr 14, 2022 9:21 pm

Let us know what you find.
2014 Bulltear (StarLab) 4x8
C&CNC EtherCut
Mach3, SheetCam, Draftsight
Hypertherm PM65
Oxy/Acetylene Flame Torch
Pneumatic Plate Marker, Ohmic, 10 inch Rotary Chuck (in progress)

engenironworks
1/2 Star Member
1/2 Star Member
Posts: 3
Joined: Thu Mar 31, 2022 9:38 pm
Location: Vanderhoof BC Canada

Re: Ohmic sensing issue.

Post by engenironworks » Tue May 03, 2022 10:44 pm

Well life got in the way for a while but I was able to spend some time on my table. I had put some thin scrap material on the table to waste while I was messing about. Turns out the torch was bottoming out just a hair before it made contact. I didn't feel to smart about that one. Oops. I reset the torch and it made a few cuts with no problem. Now as soon as the tip makes contact the break away function turns on. The torch is still being held firm by the magnets. it's not crashing into the material at all. Just doing it's normal touch off. The trouble shooting guide in the user manual is a bit vague. It says adjust the magnets. I'll have to look in the installation material. It says I can disable the function. That seems like it could cause more trouble. Or adjust the de-bounce time but that is over my head at this point. Thank you again djreiswig for your advise. You at least had me cutting again for a few minutes anyways. I'll get this dialed in yet.

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djreiswig
4 Star Elite Contributing Member
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Posts: 1438
Joined: Thu Nov 19, 2015 10:02 pm
Location: SE Nebraska

Re: Ohmic sensing issue.

Post by djreiswig » Tue May 03, 2022 11:29 pm

It sounds like you're close now. If it worked for a bit before you started getting the breakaway error, it might just be a switch or sensor that needs adjusted. Do you know what is used to detect the breakaway? Proximity sensor or maybe a simple switch? Do you have a status screen that might show the input? If so, I would wiggle the torch holder and see if you can cause the error. See if anything appears loose. If you can provide a little more information, I'm sure we can get to the bottom of this and get you cutting again.
2014 Bulltear (StarLab) 4x8
C&CNC EtherCut
Mach3, SheetCam, Draftsight
Hypertherm PM65
Oxy/Acetylene Flame Torch
Pneumatic Plate Marker, Ohmic, 10 inch Rotary Chuck (in progress)

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