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Arc OK intermitent issues on torch fire

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01 Apr 2021 22:11 #204441 by txtrone
Replied by txtrone on topic Arc OK intermitent issues on torch fire

Most of the circuits ive seen here totally negate fuses, breakers, etc. So I would consider
everything “use at your own risk, your mileage may vary, etc.” Whatever you do, please make sure you do it safely.


That is a great point! Do you have schematics of your system that you would be willing to share?

Besides the breakers on either side of my power supplies I do not have anything fused. That would be great to see a system diagram from a pro, just to gain some insight.

thanks

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01 Apr 2021 22:39 #204446 by tommylight
Replied by tommylight on topic Arc OK intermitent issues on torch fire

QTPlasmac supports the laser but I have not played with it on real hardware. Maybe over Easter.. But I don't have enough pins on the gantry to turn it on and off from the GUI :(

I have used it last two days, it works, but i have it on all the time, although it is wired to a pin on the 7i92 so i might change that.
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01 Apr 2021 23:25 - 01 Apr 2021 23:34 #204448 by snowgoer540
Replied by snowgoer540 on topic Arc OK intermitent issues on torch fire

Most of the circuits ive seen here totally negate fuses, breakers, etc. So I would consider
everything “use at your own risk, your mileage may vary, etc.” Whatever you do, please make sure you do it safely.


That is a great point! Do you have schematics of your system that you would be willing to share?

Besides the breakers on either side of my power supplies I do not have anything fused. That would be great to see a system diagram from a pro, just to gain some insight.

thanks


I appreciate the kind words, but I am far from a pro :) I am also guilty of not having things fused like they should be. In my opinion a minimum would be breakers on the mains power in, a fuse for the 24V power supply powering the field power, and probably fuses for the DC side of the power supply powering the stepper drivers. Honestly, they are cheap insurance, and I'm not really sure you could add "too many" fuses.

One suggestion I would have is to look at the wiring diagram for the Tormach 1300PL table. They sell tables commercially, and they also post wiring diagrams in their manuals to help people diagnose faults themselves. In fact, I borrowed some of the wiring on my table from their 1100S3 mill manual, (the estop contactor circuit for one) as I have one of those and I could also look at the hardware when I was confused.

Lastly, I was reminded that the diagram shows the shield wire going to ground. That is not correct per PCW:

forum.linuxcnc.org/plasmac/39899-doing-o...h-one-thcad10#180352
forum.linuxcnc.org/plasma-laser/40712-th...ions?start=30#197468
forum.linuxcnc.org/plasma-laser/40712-th...ions?start=30#197472

However, I am unsure what that looks like in the diagram because the posts seem to be a bit contradictory (in one post he says +in of the THCAD, and in the other he says "closest to the workpiece", and they are not the same connection...


EDIT: There is this one where PCW blessed it in the next post, but ever time I think back to all that, it still makes my head hurt. forum.linuxcnc.org/plasmac/40214-big-ohm...blem?start=30#184885
Last edit: 01 Apr 2021 23:34 by snowgoer540.
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02 Apr 2021 00:24 #204451 by txtrone
Replied by txtrone on topic Arc OK intermitent issues on torch fire

I appreciate the kind words, but I am far from a pro :)


From my vantage point you are. I think if you saw my setup you would connect a few wires and start cutting.

One suggestion I would have is to look at the wiring diagram for the Tormach 1300PL table. They sell tables commercially, and they also post wiring diagrams in their manuals to help people diagnose faults themselves. In fact, I borrowed some of the wiring on my table from their 1100S3 mill manual, (the estop contactor circuit for one) as I have one of those and I could also look at the hardware when I was confused.


Will do.

Lastly, I was reminded that the diagram shows the shield wire going to ground. That is not correct per PCW:

forum.linuxcnc.org/plasmac/39899-doing-o...h-one-thcad10#180352
forum.linuxcnc.org/plasma-laser/40712-th...ions?start=30#197468
forum.linuxcnc.org/plasma-laser/40712-th...ions?start=30#197472

However, I am unsure what that looks like in the diagram because the posts seem to be a bit contradictory (in one post he says +in of the THCAD, and in the other he says "closest to the workpiece", and they are not the same connection...


EDIT: There is this one where PCW blessed it in the next post, but ever time I think back to all that, it still makes my head hurt. forum.linuxcnc.org/plasmac/40214-big-ohm...blem?start=30#184885


I have been taking every ground and shield back to the 'star ground' in my cabinet. With shields I never connect the end outside of the cabinet. Grounding, as it pertains to plasma tables, has been an enigma to me from the beginning. My original electronics package was from candcnc, there was lots of talk about grounding on their forum, including the need for an external/isolated ground that is not in contact with anything else except the ohmic sense/THC system. IIRC the theory behind this was the 'noise' that exists on the mains ground would interfere with the ohmic sense and/or THC electronics..,

Thanks again for the input, it gives me a lot to work with.

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02 Apr 2021 00:43 #204453 by rodw
Replied by rodw on topic Arc OK intermitent issues on torch fire

QTPlasmac supports the laser but I have not played with it on real hardware. Maybe over Easter.. But I don't have enough pins on the gantry to turn it on and off from the GUI :(


Rod, as your attorney I advise you to install more pins on the gantry.


Which is why you have a DB15 cable not a DB9 like I do! :)
You have Spaceship V2 hardware !

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02 Apr 2021 13:57 #204501 by txtrone
Replied by txtrone on topic Arc OK intermitent issues on torch fire

Lastly, I was reminded that the diagram shows the shield wire going to ground. That is not correct per PCW:

forum.linuxcnc.org/plasmac/39899-doing-o...h-one-thcad10#180352
forum.linuxcnc.org/plasma-laser/40712-th...ions?start=30#197468
forum.linuxcnc.org/plasma-laser/40712-th...ions?start=30#197472

I just read through all of that and my head is spinning. Those posts covered earth, fire, and water without any sort of consensus in the end. "Put the shield here, no put it here, fuse it, no don't fuse it, mine caught on fire, etc, etc"

However, I am unsure what that looks like in the diagram because the posts seem to be a bit contradictory (in one post he says +in of the THCAD, and in the other he says "closest to the workpiece", and they are not the same connection...


The post directly after that one is from tommylight who had this to say. "FYI, i never connect the THCAD shield to anything, no issues so far."

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02 Apr 2021 14:09 #204503 by PCW
Replied by PCW on topic Arc OK intermitent issues on torch fire
The THCAD shield connection is not terribly important unless you have a very high EMI environment. For a high EMI environment (like HF start plasma sources) the shield should be connected to earth ground. For normal plasma the shield can be connected to the + input (low side of the voltage divider from the plasma source). This will result in the lowest amount of hum and noise in the signal.
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02 Apr 2021 14:17 #204506 by txtrone
Replied by txtrone on topic Arc OK intermitent issues on torch fire

For normal plasma the shield can be connected to the + input (low side of the voltage divider from the plasma source). This will result in the lowest amount of hum and noise in the signal.


Thanks PCW! Stay with me for a sec. Can you clarify what "+ input (low side of voltage divider from plasma source)" is. I am using a hypertherm85. I have six wires coming from the CPC port to the THCAD. Are you saying to connect the shield wire in the interconnect cable between the hypertherm and the THCAD to the +input along with the 24+ from the isolated power supply?

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02 Apr 2021 15:00 - 02 Apr 2021 15:02 #204510 by snowgoer540
Replied by snowgoer540 on topic Arc OK intermitent issues on torch fire

Lastly, I was reminded that the diagram shows the shield wire going to ground. That is not correct per PCW:

forum.linuxcnc.org/plasmac/39899-doing-o...h-one-thcad10#180352
forum.linuxcnc.org/plasma-laser/40712-th...ions?start=30#197468
forum.linuxcnc.org/plasma-laser/40712-th...ions?start=30#197472

I just read through all of that and my head is spinning. Those posts covered earth, fire, and water without any sort of consensus in the end. "Put the shield here, no put it here, fuse it, no don't fuse it, mine caught on fire, etc, etc"

However, I am unsure what that looks like in the diagram because the posts seem to be a bit contradictory (in one post he says +in of the THCAD, and in the other he says "closest to the workpiece", and they are not the same connection...


The post directly after that one is from tommylight who had this to say. "FYI, i never connect the THCAD shield to anything, no issues so far."


Like I say, lots of opinions, lots of “definitely do or don’t do this” sometimes when the person giving advice doesn’t even have and experience with the brand of.. whatever... that is being discussed.

So, the best you can do is read the information out there, consider it, and do what works best for you.

I will say, I don’t understand anyone recommending to not use a fuse. That just blows my mind. Cheap insurance. Worst case you size it too small and need to get a bigger one. Best case you don’t set your wiring on fire and burn down your dwelling.

I do sometimes feel bad for new people trying to wade through all of this. But I guess that’s part of the learning process. A lot of us were figuring it out together as we went along. Still are, honestly.
Last edit: 02 Apr 2021 15:02 by snowgoer540.

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02 Apr 2021 15:12 #204512 by PCW
Replied by PCW on topic Arc OK intermitent issues on torch fire

For normal plasma the shield can be connected to the + input (low side of the voltage divider from the plasma source). This will result in the lowest amount of hum and noise in the signal.


Thanks PCW! Stay with me for a sec. Can you clarify what "+ input (low side of voltage divider from plasma source)" is. I am using a hypertherm85. I have six wires coming from the CPC port to the THCAD. Are you saying to connect the shield wire in the interconnect cable between the hypertherm and the THCAD to the +input along with the 24+ from the isolated power supply?


That was for THC use, for Ohmic sensing, there is no connection to the CPC port at all
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