2 Steps forward...

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05 Dec 2020 01:35 #191091 by jnwinkie
2 Steps forward... was created by jnwinkie
Two steps forward, one step back….

All, so the journey so far, with the help of Tommy, thefabricator3 and RodW have seen me being able to get a plasma table that was cutting, pretty accurately, until disaster struck. In cutting some thin plate the torch crashed and the plasma cutter will no longer get an arc going. (CIG Cut40i)

In response to that I fabricated a simple breakaway torch holder, but still have no functioning plasma cutter.

I am at a cross road here (some may say an inflection point!) so am contemplating the following steps.

I am currently running the system on LinuxCNC 2.7.0 using the AXIS interface. I have been reading about the awesome work being done to deliver the PlasmaC option and wonder if now is a good time to pursue that as an option? I have read the documentation a couple of times and tried to learn some of the terminology that until now I have bee unfamiliar with.

There are a couple of things I still don’t quite get but I am sure the forum can set me straight.

Sooooo….

PlasmaC;

If I do a clean install from the ISO, if I read it correct then I still need to do all the initial setup using STEPCONF first, then call the PlasmaC function in afterwards? (is my understanding correct here?)

I am still not sure how the PlasmaC can act as the THC (if that is the right term?) unless it is somewhat like the Proma SD THC and needs some pins from my Parallel BoB to function.

Are there any other considerations I need to think about?

Plasma Cutter replacement;

I think I will go ahead with the purchase of a Hypertherm 45XP, should I try to source it with a CPC port?

Is this a wise way forward, it just seems to me to have a lot of the homework done to help dial in for quality cuts, but I say this not on experience but from what I have read.

I also assume a machine torch is possibly a better option that a hand held torch? I won’t be likely to do much, if any freehand cutting, but once again would be more than happy to seek opinions on this view as well.

Cheers John

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05 Dec 2020 01:57 #191095 by rodw
Replied by rodw on topic 2 Steps forward...
I rebuilt my config from scratch recently for Plasmac but just cleaned up my config so I had a simple working config by hand before I started. I would probably upgrade to 2.8 and get your config working again. You will need to change your hal file for the different spindle and modify your joint axes config to use the features of 2.8

Once up and running, delete all the plasma specific parts and run the plasmac configurator

It should not be a big job
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05 Dec 2020 02:28 - 05 Dec 2020 02:29 #191100 by snowgoer540
Replied by snowgoer540 on topic 2 Steps forward...
Sorry to hear about the disaster. I am not really familiar with your table, however I'll do my best to answer your questions without the specific knowledge.

If I do a clean install from the ISO, if I read it correct then I still need to do all the initial setup using STEPCONF first, then call the PlasmaC function in afterwards? (is my understanding correct here?)

Assuming you're using a parallel port for your table, yes STEPCONF. Once your table is set up, you will run the configurator which will "install" the PlasmaC component on top of the GUI you chose.


I am still not sure how the PlasmaC can act as the THC (if that is the right term?) unless it is somewhat like the Proma SD THC and needs some pins from my Parallel BoB to function.

For THC, you can either provide an arc voltage to PlasmaC, and it will do the rest to control the torch. You would need a Mesa THCAD or similar to do this. Alternatively, if you have an external THC, you can provide PlasmaC the appropriate up/down signals for THC.

I believe you are mostly referring to the first option. In this case, in a broad nutshell, PlasmaC takes the supplied voltage input, and uses it with the help of a PID to determine if the torch needs to go up or down, and then makes the appropriate corrections. One of the nicest things about PlasmaC is the ability for "auto volts" which takes the guesswork out of setting a voltage. PlasmaC will sample the voltage after an interval (which is changeable) and then strive to maintain that voltage (i.e. height) throughout the cut. This is good because many plasma cutters either dont have a reference voltage to start with, or in cases where they do, are often based out of a lab, and you really don't know if you're cutting the exact same material under the same conditions. AutoVolts is pretty awesome.


Are there any other considerations I need to think about?

Probably. For starters if you plan to use a THCAD, while it is possible to do it with a parallel port, you do need to slow it down. There are posts lurking around here for settings to try. Many of us run Mesa 7i96's or similar.

If you do want to run a THCAD and do buy a PMX45, I recommend a THCAD-10, and changing the voltage divider to 20:1.


I think I will go ahead with the purchase of a Hypertherm 45XP, should I try to source it with a CPC port?

Absolutely, 100% yes. If you have extra coin to throw at it, get one that comes with the RS485 communications. PlasmaC has the ability to change amperages on a Hypertherm machine if the machine is equipped with the RS485 stuffs. You could always add that later, but best to do all at once I think. Might save you a few bucks too. To do the comms, you will need a USB to RS485 converter, there's a recommendation for one that is known to work in the user guide.


Is this a wise way forward, it just seems to me to have a lot of the homework done to help dial in for quality cuts, but I say this not on experience but from what I have read.

I think plasma always comes with homework. But Hypertherm will definitely cut down your time messing with it to get good cuts.


I also assume a machine torch is possibly a better option that a hand held torch? I won’t be likely to do much, if any freehand cutting, but once again would be more than happy to seek opinions on this view as well.

yes, it is much easier to keep perfectly perpendicular to the workpiece, which makes a big difference. It will also make it easier to mount.


Hope that helps, let us know as/if you encounter more questions, always happy to help!
Last edit: 05 Dec 2020 02:29 by snowgoer540.
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05 Dec 2020 09:54 #191111 by jnwinkie
Replied by jnwinkie on topic 2 Steps forward...
Thanks Snowgoer540 and Rodw. Do either of you know if this card can be sourced in Australia?

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05 Dec 2020 10:12 #191112 by rodw
Replied by rodw on topic 2 Steps forward...

Thanks Snowgoer540 and Rodw. Do either of you know if this card can be sourced in Australia?


THCAD? I might have one in Brisbane. You can contact me on the sales email on my web site www.vmn.com.au/
My mobile is in the contact us page. Feel free to call me.
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05 Dec 2020 11:40 #191119 by snowgoer540
Replied by snowgoer540 on topic 2 Steps forward...

Thanks Snowgoer540 and Rodw. Do either of you know if this card can be sourced in Australia?


Any time; happy to help.

Perhaps one of these makes it easier than the US source?

forum.linuxcnc.org/27-driver-boards/34979-mesa-suppliers
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