MPCNC plasma cutter

[MickeyW]

This has been an interesting read. Thanks Chris and everyone else that has chipped in.
I started printing the latest MPCNC Primo kit a few weeks ago with a view to use for plasma cutting. The electrical interference problem seems to be common, and various youtubers have tried different tricks to minimise the effects.

My build has been printed on a Creality Ender 3 v2. It's not the fastest, but I'm very impressed to have not had a single failed print. The biggest marathon print was the core that took 33 hours!

This is the latest picture I took. The belts have since been fitted and fastened.

Wiring up is on the cards once I've decided on what control system to buy. I'm looking to use the 1/32 step DRV8825 drivers with RAMPS 1.4. Common advice seems to be to get set up with the low cost equipment rather than kill more expensive kit while experimenting. Chris I'll be interested to know if you find the genuine Arduino any more reliable than the clones.

 

[Dev]

Good stuff. I have a straight tip and mounting to make mine plasma but it’s being gainfully employed at the minute.

 

[chrisg3103]

I'll be interested to know if you find the genuine Arduino any more reliable than the clones.

Well I haven't tried the cheapo Arduino since I swapped it so can't say for certain, but genuine one isn't too dear. Electronic failure is very annoying

 

[Thatnewguy]

Thought this might be of interest, not seen any mention of the MPCNC on here but its pretty cool, and cheap!
The aim of this was to make a super cheap CNC plasma cutter, but things snowballed... adding up what i have spent, taking away the fails and fancy bits i recon you can have a functional CNC platform for £150, if you have a 3d printer. This is what i did with it:

first off this is the home of the MPCNC - https://www.v1engineering.com/

I started off just wanting a small scale dodad i could stash away when not needed, instead of having a dedicated table and whatnot, so set off calculating the maximum size i could make it from 2 x 3M lengths of conduit. Think it was about 720mm square with a working area just shy of 500mm square, there is a cut calculator available. I wont go too much into detail about the nuts and bolts as its done to death on youtube and the MPCNC forums.
To try make my portable idea i first made an angle iron frame.
View attachment 199372
The parts will take many many days to print, and the best part of 2 spools of filament, you will end up with a pile of bits like so:
View attachment 199373
dosnt look like much but the tall parts in the top corner were 13 hours each!
View attachment 199374
Quick mockup, just because.
View attachment 199375
rails largley assembled, squared and bolted to the frame, all seems fairly rigid.
View attachment 199376
Moved inside, because its cold. This was first test fire of the cheapo ramps and motor drivers, a few teething issues having to install a usb driver onto the computer so the knockoff arduino would talk to it but got there in the end and got some movement.
Now this is where things took a turn for the more expensive, it started to look like a real thing so i started trying to improve it, mostly cable management. As it stood that would of worked fine as a machine, but i wanted a nice control box and stuff. so here is a cost breakdown for the base machine:

25mm conduit (from screwfix) - £21
PLA 2 spools - £30
steppers - £45
RAMPS stack, screen + drivers - £19.50
lead screw + nut - £7
60 Bearings - £12
Motor pulleys + belt - £9
coupler - £6
Ribbon cable - £4.50
Dupont connectors+tool - £20

So thats £174, but i included the cable and dupont connectors i used to extend the stepper wiring and make the splitters. If you have some of this stuff already all the better, or if you go a different route. Also some of the things can be found much cheaper, thats just what i paid for convenience, the curse of amazon prime... if your not so impatient and shop around you can save a few more £
More in pt 2

Great job Chris. While I know this is an older thread I have a quick question. In the pic where you added the relay (ssr 40 dc to dc I believe), I cant see where the wires go to. It looks to be a + and - so I would assume the + would go to the trigger output wire, so would the - go to chassis ground? I have purchased a pilot arc Low frequency unit that I am hoping will aid relief in some of the problems that you had. thanks

 

[Erie Fred]

Cutting 3mm steel at 1200mm/min, first one was set to 1400 and was far too quick, lots of sparks and surface just gouged.
But fairly neat cut and the dross came away very easy, bit of a chamfer but this isn't a high end torch or machine by any means. More importantly no electrical failures maybe luck? Maybe the kopex helped I'll take it anyway, now a bit more confident to try some other parts

Cut edge shows too fast travel, drag angle should be much less, slow down.
Will improve cut edge squareness as well.

Don't adjust speed for less/more slag, work for accurate parts.

 

[chrisg3103]

Great job Chris. While I know this is an older thread I have a quick question. In the pic where you added the relay (ssr 40 dc to dc I believe), I cant see where the wires go to. It looks to be a + and - so I would assume the + would go to the trigger output wire, so would the - go to chassis ground? I have purchased a pilot arc Low frequency unit that I am hoping will aid relief in some of the problems that you had. thanks

I can't really remember I have a bad habit of getting right into something, then forgetting all about it and how I did it. Easiest way will be to have a look at it later, it's still there, but suffering from horizontal surface syndrome at the moment

 

[chrisg3103]

Must admit I had to go though this thread a few times untill I found a picture with the relay, I think I know what your saying now. The cable going off screen goes to a 2 pin connector on the front of the plasma.

Like so, just a switch, no need to worry about polarity.
Also I seem to have fitted a conventional relay at some point, no idea when!

 

[Thatnewguy]

Must admit I had to go though this thread a few times untill I found a picture with the relay, I think I know what your saying now. The cable going off screen goes to a 2 pin connector on the front of the plasma.
View attachment 385068
Like so, just a switch, no need to worry about polarity.
Also I seem to have fitted a conventional relay at some point, no idea when!
View attachment 385070

I see, I think LOL. it looks like you have 2 wires ran from your ramps boards(both look to be off d9( which on my ramps is 12v+ all time) so i guess leaves me a bit confused because the 2 pin connector on the plasma are the 2 wires coming from your original gun that make a connector or jumper that completes the circuit to arc. So do you think i need to figure out how to shut off power to d9, or is that what the commands in estl cam are doing. I feel like it should be opposite but i'm half stupid hehe

 

[Thatnewguy]

After doing some research, it may seem I have to edit my firmware in marlin to make it think its controlling a spindle?

 

[chrisg3103]

Think I'm with you now, don't think I had to edit the firmware, just add a start and stop command in the g code for d9. Look back at post 5.

Yellow negative, must of ran out of black.

 

[Thatnewguy]

so for whatever reason my d8 d9 d10 were all + power all times. I went ahead and reflashed marlin under to
#define MOTHERBOARD BOARD_RAMPS_14_SF (s being spindle and f being fan) and though spindle is very erratic, fan works on d8. I may have to play with the delay times for arc but i will prob have to reflash again as i never set my bed size perameters anyhow. Thanks for your help. Once I get everything going I will probably make a simple video on my youtube channel to help sort this stuff out. Thanks Chris you rock

 

[Erie Fred]

If I read this right, your trigging the plasma on, but your not getting the "o.k. to move" signal back from the plasma supply ?

 

[chrisg3103]

No feedback from the plasma in this setup, it's very basic. Mention the delay in post 44 as a bit of adjustable g code you add to estlcam, let's the plasma pierce for say 0.7s before the move starts.

Just a thought but are you measuring voltage between the two pins at d9 and so on? Think these things switch the ground rather than live, so if your measuring between supply ground and pin d9 live it will probably show always live. Could be wrong, been a while, post up a link once you get it going

 

[Thatnewguy]

If I read this right, your trigging the plasma on, but your not getting the "o.k. to move" signal back from the plasma supply ?

sorry just happen to see reply. I am triggering the plasma via the fan output on a spindle/fan(sf) setup utilizing m106(on) and m107(off). there is just a half second or so lag from when the plasma starts to move and then ignites to cut

 

[Thatnewguy]

No feedback from the plasma in this setup, it's very basic. Mention the delay in post 44 as a bit of adjustable g code you add to estlcam, let's the plasma pierce for say 0.7s before the move starts.

Just a thought but are you measuring voltage between the two pins at d9 and so on? Think these things switch the ground rather than live, so if your measuring between supply ground and pin d9 live it will probably show always live. Could be wrong, been a while, post up a link once you get it going

yes i think you are right that they switch via ground but i am testing through both + and - on d8. I will check out post 44 as that sounds like the ticket. I have a tendency to skip over things