The blacksmith's plasma table

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31 Mar 2024 10:10 - 31 Mar 2024 10:14 #297268 by polskleforgeron
Hi everyone,

I'm a blacksmith/metalworker with my own shop, and I'm in the process of building a CNC plasma table and I thought I would create a subject on this board to help me go through the electornic part which scares me a little.

I'd like to use LinuxCNC to run it with a Mesa7i96s and Mesa THCAD, and an old computer I have. I've found this subject which seems to be really helpfull (with a complete wiring diagram) : forum.v1e.com/t/lowrider2-plasma-build/13939/4

I'm a bit lost though because electronic is a bit complicated to me and would like some precision about how this thing works.

First I understand the needs for a floating head. I also understand that it can be build with a limit switch. I'm not sure though how it goes in the grand scheme of things. Do linuxCNC already knows how to use a floating head ? Is it as simple as telling LinuxCNC which pin of the Mesa 7I96s is connected to the limit switch of the floating head and teeling it the distance it has to go up after the switch is triggered, and then use Gcode to tell the plasma to probe the distance before each cut ?

Also I currently own a Stalhwerk cut 70 which I believe is HF. From my lecture on the subject a HF CNC plasma is really not a good idea. I'm ready to sell it and to buy another plasma CNC compatible (I'd like to have already pins on the plasma because I dont trust myself opening it and playing with voltage dividers etc, as I said I'm not confortable with electronics, even though I try to learn). Hypertherm is not really an option as of right now because of the price. I believe Stamos make a CNC compatible plasma cutter for a bit less than 700 euros.

Could someone confirm that I should wait to know which plasma I'll use before I buy the THCAD as I believe it depends on the arc voltage coming from the plasma (some already have a voltage divider, other not) ?

I'm really sorry if my questions sounds messy, I'm not a nativ english speaker and I'm a bit lost with the huge sum of inormations (sometimes which contradict themselves) I find on the internet. I would greatly appreciate any ressources you have which could help me in my project. Thank you very much for reading me. I plan on updating this subject as the building goes.

Some pictures of my 3D model and the start of the build (I'll replace the 3D printed part with aluminium one's once I've validated the build):



 
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Last edit: 31 Mar 2024 10:14 by polskleforgeron.

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31 Mar 2024 12:48 #297277 by tommylight
I have used both of those plasma sources, both are quite good, and both can be used with CNC, granted Stahlwerk will requiire opening it and wiring in the THC and torch on and if you want the ARC OK modification as described in the PlasmaC documentation.
Stamos has connectors so much easier to wire in.
Get the THCAD 10 or 5 or 2, not the 300, and also get 2 resistors of 1MOhm value at 2W, this can be used with every plasma source.

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01 Apr 2024 07:08 #297341 by polskleforgeron
Thank you very much for your answer, I believe I need a relay for the torch on and off if I go with the stahlwerk ? (I actually would like to since it prevents me having to buy another one). Also, is it hard to wire the THC and the arcOk signals in the stalhwerk ? Do you happen to have a picture of the set-up ? I believe I can try to manually turn on the plasma close to the table when I've wired all the step mottor and limit switch and see if I have EMI problems right ?

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01 Apr 2024 11:45 #297358 by tommylight
The info on how to make a hardware ARCOK signal using a reed switch is on the PlasmaC primer/documentation with pictures.
For wiring the THC, get some pictures of the insides of the plasma source, it must be wired to the rectifier outputs.
To test for interference, fire the plasma from 3-5 meters away from the machine while the machine is running some gcode, then try closer and closer. As a final test i put the torch cable over the electronics box and fire the torch normally near some metal, then fire the torch in mid air, then fire the torch touching the material as this makes the most interference by dumping all the power through the cable only.
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01 Apr 2024 14:13 #297372 by polskleforgeron
Would you have an advice for the drivers ? I have two Nema 23 (3A) for the Y axis, a nema 17(1.5A) for the X axis and a nema 17 (0.5A) for the Z axis. I think I'm gonna buy the electronics soon so I can start to configure LinuxCNC and see if everything's ok movement wise before I start to dabble with the plasma and THC. I heard gecko's one are good but they're pretty expansiv.

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01 Apr 2024 16:09 #297381 by tommylight
Get the cheapest drives, those named "TB6600" that use TBxxS109 chip, they are very good and better than the rest of TBxxxx drives, usually rated as 4 or 4.5A (the real TB6600 is rated at 5A), for 12-15$ a piece they are magnificent, i have many of those in daily use and the only issues i had with them was the DIP switches on several of them were faulty and caused a lot of headache to figure out, and one had a poor solder on the DIR optocoupler.
Later, when you get some experience, you can splurge on LAM Technologies drives, they are top of the line and cost only a bit more than Gecko, although www.mechapro.de has them often on discount making them cheaper than Geckos.
www.mechapro.de/shop/Schrittmotor-Steuer...ehaeuse:::22_49.html
I usually get the DS1044 and/or DS1076, and they appear to still be cheaper than Gecko.
Do not forget to get the programmer for them, it is at the bottom of that page, costs 28 Euro.
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01 Apr 2024 17:51 - 01 Apr 2024 17:57 #297391 by polskleforgeron
Man you're precious. Thank you a lot for all these usefull informations. Just bought the Mesa 7I96S and the THCAD-10. Was a bit of a pain to find in europe but finally found it on eusurplus (funny how my google search always end up on one of your answer on another subject). I'm glad I can buy cheap drivers because the Mesa cost more than what I was expecting with taxes and shipping. I've read the plasmaC documentation. I'll take a picture of the inside of the plasma cutter when I have time. I'm still hesitating if I buy the Stamos or try to fiddle with the Stahlwerk I already have. I would learn more thing using the stahlwerk, but i'm afraid to break something, or worse, injure myself with these high voltages.

Thank you again, I'm a bit lost in this project and it's reassuring having someone to help a bit ! Yet, I'm exited. This plasma table will be really usefull in my work (and will save me countless hours with the grinder), and understanding how to do CNC stuff by myself is very rewarding.
Last edit: 01 Apr 2024 17:57 by polskleforgeron.
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09 Apr 2024 13:25 - 09 Apr 2024 13:29 #297863 by polskleforgeron
Hi man.
I have received the Mesa cards, ordered the driver and a 36V alimentation. Do you think I can use a basic 5v alimentation which came with an Arduino to power the Mesa 7i96S ? Or use something like a USB phone charger or should I buy a better alimentation ?
Also I'm not sure what should I buy to wire all the electronic, between the cards and the driver etc. Does simple electronic wire I have laying around can do the trick ? I believe there isn't much power exept in the motor circuit after the drivers.
If you happen to know the english name of those nice connectics (with the 4 pins for the motor and such) so I can order some that would be greatly appreciated. I'm gonna buy good shielded cable for the motors and the end-switches.

On another note I think I'm gonna use the Stamos. I have someone willing to buy my Stalhwerk and it reassure me a bit to not have to fiddle with the plasma on top of wiring all the cards and the driver. And It eliminates a big source of EMI.

I have pretty much all the different elements exept the wiring cables and the plasma and it cost me around 850e, almost half of it being the Mesa cards (withtaxes and shipping cost) so I really hope I'm not gonna fry it like a dumbass.
Last edit: 09 Apr 2024 13:29 by polskleforgeron.

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10 Apr 2024 04:36 #297895 by rodw
Replied by rodw on topic The blacksmith's plasma table
Grab a 5 volt DIN mount power supply from Meanwell or similar. I have seen many issues using usb/phone chargers
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12 Apr 2024 09:43 #298051 by polskleforgeron
One gave me a big electrical shelf, all metal, with grounding wire and big coper bridge. There is plenty enough space to put both the electronic and the PC inside, I would drill hole for aviators connection to the motors and plasma cutter so the shelf can be moved independantly from the plasma table. Do you think it's a bad idea to have both (PC and electronic) in the same place ? Do you think it would be usefull to try to shield the electronic from the motor alimentation ?

I'm almost done with the mechanical part of the build, have received the drivers and the motor alimentation. Still lacking the 5v DIN alimentation and the limit switches. Hope I can soon start to wire everything and try the XYZ movement.

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