Project Overkill: CNC Plasma

Hey everybody. Been reading here for a while and I have to say I’m as impressed as everyone else with the ingenuity and effort that went into the MPCNC/variants.
I know it isn’t a MPCNC of the original design, but, inspired by Ryan’s efforts, I decided I was going to try my hand at designing and fabricating my own CNC plasma table featuring printed parts. It isn’t complete yet, but I’m getting into the wiring at the moment. Thought you would enjoy some pictures and progress of the build thus far.

Design goals
-Entirely my own design
-Use Fusion 360 for CAD/CAM with post processing as needed.
-Made from available materials.
-V groove, ball bearing rollers on square tube tracks to prevent racking, minimize contact area, and hopefully maximize stiffness in the rails.
-Reversible/removeable slat table because I wanted to see if I could and it lets me use both side of the slats with a repeatable-ish plane to about 0.125" flipped side for side.
-Use my existing plasma cutter (Lotos LTP5000D) with an adapted machine torch (I know, HF start. I’ll get to that.).
-Dual shielded wiring (foil liner and outer tinned copper braid).
-Marlin Firmware to start (it’s what I’m familiar-ish with) with dual end stops to self square the Y axis.
-BTT GTR Board (allows additional motors I may need later).
-4’x4’ cutting area with 3.5" water table.

Stuff I plan to add later:
-5 Axis machine head for cutting bevels.
-I plan to make a custom superflex hose to add some length/flexibility to the cable later. It’ll also allow me to swap back and forth between the hand torch and the machine torch pretty quickly.

Some details on the build:
It’s made from industrial steel cut offs from the metal yard (I’ve been a hobby machinist and welder for about 15 years now) because it was $0.30/lb. Who can argue with that right?
The legs are 5"x5" square tube, angle Iron is 4x6, and the slat table is 1x1 angle with 1/8x2 slats. The pipes running the length are to reinforce the center of the bed (I plan on cutting 1/4-1/2" plate for another project), and to allow the slats to expand in a controlled linear manner when they get hot that doesn’t change the surface height of the slats. Everything except the legs are 1/4" thick. Those are 3/16". Oh, and the X gantry rails are 1x1x1/8"wall aluminum for weight. As it sits I can barely push on the x gantry and it’ll go halfway down the table. So under power from the 2A Nema 17’s it’ll be smooth sailing, or rather rolling.

Anyway, you guys just want to see the pictures I’m sure. If you have any questions or want the STEP files to build your own, you’re welcome to them. I’ll post them on Cults or something if there’s interest. I also have a couple of questions as well if you guys with experience would be so gracious as to offer your advice.

Since it isn’t one of Ryan’s designs I wasn’t really sure where else to put this thread other than a build forum, but if it’s inappropriate or poorly placed, feel free to move or remove as needed.

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I’ve actually shortened the Z axis a bit since these pictures (new parts printing now) in order to gain some Z clearance back. I’ll be able to cut on the top of 5" tube in the 3 axis configuration, and roughly 2" in the 5 axis configuration when I get around to that.

And before I forget, the motion controls will all be in that power junction box on an old monitor swing arm I had, and completely isolated from the frame of the table with rubber grommets through the bolt holes in the box.
All of the electronics will be mounted to what use to be a cutting board (oops) spaced off the box with nylon spacers.
I’m using aircraft connectors through the wall of the box, and will mount the TFT on a plexiglass face plate. Because it’ll look neat, I’ll have access to the SD Card slot and maybe I’ll add some LED’s. :grin: It will also feature inlet and outlet 80mm fans to keep the electrons happily flowing.


All parts are printed in eSun ASA on my modified Anet A8 Plus.
It said it was UV resistant, so I figured it was a good choice for a plasma table.
I will be adding welding curtains around the perimeter before it’s operational.

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Questions I have at the moment:

  1. I think I’ve read every thread on here relating to plasma use, but I’m still confused on what wire goes to what lead on the relay from the plasma cutter. The LTP5000D is a 3 wire trigger. Anyone have pictures or an explanation of those wires please?
  2. What is the consensus on what pin(s) to use to trigger the relay? An existing laser trigger pin in the firmware seems like the simple solution, but basically anything 5V should work, right?
  3. For the tinned copper braid on the outside of my wiring, should it be grounded to the motor frame AND the aircraft connector? The ground bar inside the box will be screwed directly to the metal box and use the ground from the 110v power cable for grounding the box and subsequently the shielding on the motor/end stop/relay wiring. Or am I creating one of those ground loops? I know nothing electrical (other than the plasma cutter itself) will have any electrical connection to the table, but I know EMI is radiant from the cheapo plasma cutter I have. I do plan to get a better one later, but it’s not in the budget at the moment. I’m just working with what I have.

Sacrificed an old cutting board for the mounting plate for the electronics. Instead of going through the annoyance of assembling blind with stand offs, I just put some threaded rivets (“nut-serts”) in the box so I can add screws from inside the box AND they give the board standoff from the box.
Not quite so lucky with the stand offs for the electronics. I just drilled and tapped the board, then used some small aluminum spacers.

Next comes the aircraft connectors/fan holes through the bottom of the box. Just made a quick template in Fusion.

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Getting some progress on the control box. I got the fans, power switch, and panel connectors for the motors and end stops in. Even put a “oh sh*t” button up top for when I inevitably mess up.
Still need to make a frame for the 7" touch screen and put it in the lexan cover though.
Once all that is done, I get to mess around in VSCode. Yay. :unamused: (not my favorite thing). Just have to reassign the dual Z pins as dual Y pins, define the end stops to match, and a few other things.
Why a 7" touch screen? Why not? I’d really like to be able to plug an Xbox controller in to jog it around, so if anyone knows how to do that I’d love to learn.
Anyway, on to the pictures.



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Well I’ve hit a bit of a wall. I was printing a case for the touch screen and my printer decided not to play nicely any more. Currently looking into a replacement. I’ve just had it with fixing up the cheapo printer.

Anybody use a Voron 2.4 here?

That is a pretty new printer. From what I’ve seen, it is really good printer, but with a very tiny workspace.

The common answer here is that the prusa mk3 is an excellent workhorse. And then people think that the ender is a better choice because it is 1/4 the price. And they are right, but it doesn’t “just work” like the prusa does.

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Get the Prusa Mini, the new one has even got a better sensor than the one I bought and I am still really satisfied with it.

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The one I was looking at on their site said there were up to 350x350mm build plates (I don’t need it that big at the moment, but go big or go home I guess?). My current printer is 300x300.
I’ve read great stuff about the Prusa printers as well. I’ll look into them!

Maybe I am thinking of a different voron. I have seen some videos of a very tiny one printing crazy fast with great quality.

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Oh they do have a Voron 0 that’s really small. A whole bunch of people on YouTube are doing this “speed boat” challenge to make a benchy as fast as possible and producing some really impressive stuff.

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Nice build so far, I like it. I’ts simple and elegant.

Will you use a torch height controller?
Also, be prepared to fight HF interferences, I had a very hard time getting mine to work, apparently a better/more epensive plasma cutter helps tremendously.

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Thank you! I definitely read your threads several times planning this thing.
I’m doing my best to mitigate HF interference by having all of the motion wiring be double shielded, in cable chains, and electrically isolated from the table itself.
I don’t plan on using a THC at the moment since I only intend to cut thick plate with it (between 1/ and 1/2 inch thick). Eventually, I’d like to have a THC and a hypertherm plasma cutter to give some flexibility to what I can cut, but it’s not in the budget at the moment.

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Well, after considering the options, and as much as I would love a voron or a prusa, I decided on an Ender 5 plus and microswiss direct drive/all metal hotend kit from matter hackers. I already have a spare SKR 1.4 Turbo and a BL touch I can put in it too. It has the size I want, and has good reviews without putting me in the poor house. So I’ll limp the A8 Plus along for a couple days if I can. Poor little thing had a long life.
Hopefully I’ll be back up and running soon. Thanks for the inputs guys.

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Ok. I think I’m screwing this up. I figured I’d get the computer work done while I wait on my new printer to show up, but I need some adult supervision with VS code please. I think I just bit off more than I can chew with this GTR board and humble pie tastes batter than a crap sandwich. I get ALL the errors. Like a high school english paper with red pen all over it. I’ve tried to uploaded my current files so you can dig around in them.

My base firmware is the SKR Pro Dual (not the LR) from the MPCNC GitHub. In VS code I’ve added the new board and changed the default environment to match. It’s also set up for the TFT 70. I enabled Y2, and disabled Z2, swapping the pins file around where the original dual Z steppers plug in to be the Dual Y, and making the old Y pins into the new Z (I think I did this successfully). I’m using the Servo pin (PB11) for the BL Touch as my “laser” enable pin with the Gnd going to DC-, 5v going to DC+, and PB11 going to Int on my relay. There was no Laser enable in the pins file, so I copied the text from the Marlin page about spindle/laser enable feature and put it in there at the bottom. Also, the Marlin site suggests a 1-10k resistor in line with the spindle enable. Since I can turn the plasma on after the machine is powered up, is this necessary? With the plasma off, it should just trigger the relay and do nothing, correct?

For the dual end stops, I have the original X/Y/Z in place, and use the YMax for Y2. Should I be wiring the two Y end stops in series instead and plugging into the original pins?

If it matters, I’m using TMC 2209 drivers in UART mode. I’m also using Marlin 2.0 Bugfix last updated maybe 2 weeks ago?

What am I doing wrong? I appreciate the help.
Overkill Plasma.zip (76.5 KB)

I would say step back. Start over.

Flash the base firmware with zero edits, does it work and flash? Does everything work?

After that, Your pin swap is not needed. Just enable the axis you want and disable the next, flash, did it work? No pin edits are needed anymore.

After that tell us what is needed next.

Ok. I just downloaded everything again. Clean slate.
Just from opening the folder in VSCode I get a whole bunch of errors. Does not compile.

Changing nothing else but the motherboard and default environment drops me down to just one error about the dreaded squiggles. This doesn’t compile either.

Regarding the pin swap, it was more for organizational purposes than anything. On the GTR board it’s already configured for a single driver with dual outputs on what is supposed to be the Z axis. Just figured it would be convenient to swap the Y axis in there if it’s just a matter of swapping the pin assignments. Otherwise, I just enable Y2 and disable Z2 and go with whatever pins it spits out, correct?