MPCNC plasma cutter

[chrisg3103]

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.

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:

dosnt look like much but the tall parts in the top corner were 13 hours each!

Quick mockup, just because.

rails largley assembled, squared and bolted to the frame, all seems fairly rigid.

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

 

[Dev]

Looks good. I bought a cheap plasma with a view to making the same thing myself so I’ll follow your progress with interest.

 

[kcchan]

Very interesting, I’ll be following this with interest

 

[chrisg3103]

Got a bit more time so here is the rest of the story so far,

Once i saw the thing had possibilities i started to tidy it up, make a few bespoke parts to get the wiring sorted and so on, the plan was to run the X and Y steppers in series, as described on the mpcnc site and just run them into the ramps board with the dupont connectors, so one driver moves two steppers as one.
But then i read up on the dual end stop configuration, this is when each stepper has its own driver and additional end stop. This allows for the machine to auto square its axis on startup!
So to do this each stepper had to have its wires extended to reach the ramps board, so twice as many cables, plus the end stop wiring.
Looking into cable management quite a few folk used printed cable chains, which are all well and good but time consuming to print and clunky, then there is the fact they usual run them along the table the machine is bolted to, which i dont have. While looking about i saw a post about using a steel tape measure as a cable chain! its a brilliant idea



So i bought a roll of 1/4'' cable braid which is also awesome for cable management, and mangled an old tape measure to try it out,works great. The only issue is i will need 3 cables to be running in the X axis, so had to buy a beefier tape measure to sacrifice.
Bought a 25mm tape measure and some 20mm cable braid to go over it, designed a few mounts in tinkercad (still learning fusion) and:



Hey pesto, ultra light weight low resistance cable chains!
The cables will travel towards the sort of docking post in the bottom right, then down through a hole cut in the rail/tube and out.

Quite pleased how the pivoting Z axis mount came out


One tidy looking mpcnc machine, i now love cable braid

First motion test with it pretty much ready to roll

The obligatory crown, im quite glad i set it up with the pen rather than a plasma torch, there were a few issues to sort...
first one being the axis got switched somehow, its simple enough to fix, you flip the plug on the ramps, i am currently using the series configuration of steppers until all the bugs are ironed out,can then move onto the more complicated dual end stop configuration, but the wiring is now there.

Another issue was the fact that my super cheap ramps came with a4988 drivers, which work fine, but can only go as low as 1/16 stepping, the mpcnc firmware is setup fr 1/32. So all my movement were doubled! combined with the axis mixup it crashed a few times.
Quick firmware tweek and was fine, need to change these settings:

default is 200, 200, 800, 200

Or if your not so cheap and use 1/32 stepping drivers you dont need to do anything

 

[chrisg3103]

So, now thats working it was time to move back into the garage, my wife is tolerant but even i draw the line at sparking up a plasma cutter in the house

speaking of which, the plasma cutter..
I have a nice little old hypertherm max20, it has a pilot arc and thought i could maybe convert the torch to the cheap Chinese ones, as you can get a machine torch real cheap. Long story short, nope. Hypertherm uses a blow back torch to start chinese ones use a mashup of HF and switching as far as i understand. So thought what the heck, ill buy a generic Cut50, few days later it turns up, and i find this in the fuse holder:



Now to be honest if i hadnt seen someone post this already i wouldnt even of thought to check there was a fuse! if you have a cheap plasma id check your plug..
New plug later im away, but the torch supplied wasnt starting the arc very easy, fizzing and popping. Thought id try the torch i bought to try convert the hypertherm, worked brilliant at pressures up to 7 bar! So plasma works.
Used the duff torch to wire up the machine torch i got, modified a design to print some mounts to get it on the machine and was ready to roll with the main event.

Now the software im trying is estlcam, its free but will start getting you to try and buy it after a few uses, fair enough.
It seems fairly intuitive, like any new thing it will take time to figure out,one thing i managed to get working was the plasma start stop commands.
First off i wired a solid state relay to D9 on the ramps board, think this is usualy used for an extruder fan? solid state relays seem to be recommended due to no arcing contacts to screw with the electronics, not sure how relevant that is but i got one anyway.
In estlcam you just need to do this:

And all going well you get this:

A failure Seems the machine torch was behaving like the duff hand torch? it lost the arc halfway though the cut and that fizzing and popping is it trying to get going again, but that HF noise really screwed with the ramps and it reset, not so good

take 2

Managed the cut but lost it at the end

Turned down the air pressure to about 3 bar and it finaly worked

Seemed stable but a few more tests after that and it was very temperamental, a bit annoying but the HF when it looses the arc makes everything go mad.
I saw a youtube video where someone was describing similar problems with their hand torch, and that when the electrode was loosened off and brought closer to the nozzle it worked. So cut a nozzle in half to see what was going on in there.



Tried the nozzle on the good torch and the machine torch and the electrode was set further back in the machine torch.
So took a little bit off of the machine torch to even them up



Nope, just the same unreliable result. I have tried swapping the power hoses, pilot arc wires, consumables. Measures resistances and nothing i can find will indicate why one works great and one gives up at anything over a few bar of pressure?

One last roll of the dice, i accidentally bought a non pilot arc torch when i was starting out. So thought why not try that? i just need to run the pilot arc wire to the nozzle, except for some reason the pt31 torch head wouldnt fit the power hose!
I wast throwing more money at it so managed to get it sort of centred in the lathe and turned down and cut a new thread



got it hooked up and ran a shoddy looking wire to the nozzle


used the trigger for the hand torch to fire it and it worked every time! got a bit stuttery at 6 bar but i have no intention or running that high.
So thats it up to date, another pair of torch mounts are printing and this one shall be tested this weekend at some point. Its annoying i cant get the AG60 to work, its a much beefier torch

 

[willie.macleod]

Looks great, what 3d printer did you use and how many restarts did you have?!

Very tempted. Keep us updated.

 

[ajmoore1]

Looks good. Can you make me one.

 

[chrisg3103]

I have an Ender 3 and my good old Anet A8. The majority was done on the ender but the anet did a fair bit, its just slower. Purple is ender and silver is anet.
Amazingly no print fails If you dont have a printer the anet is only about £110 or the ender £150

Looks good. Can you make me one.

Dont think i will be producing any of these any time soon, has taken a couple of months of stolen moments to get this far! pesky job and family

 

[daedalusminos]

Very interested in this...might have to fire up the printer. Would probably go for ABS over PLA but that's just preference.

 

[Barking Mat]

Most impressed. Nice work.

One day.... I'll try and do the same.

 

[decca]

Thanks for posting this Chrisg, very interesting.

 

[ukracer]

Very interested in this...might have to fire up the printer. Would probably go for ABS over PLA but that's just preference.

You ain't got an Anet or an Ender 3 then?

 

[daedalusminos]

You ain't got an Anet or an Ender 3 then?

No heated bed?

 

[ukracer]

No heated bed?

Heated beds yess. But they take an age to heat up and without an enclosure won't hold temps and allows warping.

 

[decca]

Don’t suppose you could post links to some of this stuff could you please

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

Im sure it will be of interest to quite a few people on here.

 

[chrisg3103]

steppers - £45 https://www.ebay.co.uk/itm/5PCS-59N...212812&hash=item1cb55cc7c7:g:QTYAAOSwyQtVjhcX

RAMPS stack, screen + drivers - £19.50 https://www.ebay.co.uk/itm/3D-Print...507383&hash=item56c5fe93be:g:qP0AAOSwSVRdAgVI

lead screw + nut - £7 https://www.amazon.co.uk/gp/product/B07LDZLD2M/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&psc=1

60 Bearings - £12 https://www.ebay.co.uk/itm/10-Red-8x22x7mm-ABEC-5-608-2RS-608RS-Skateboard-Roller-Sealed-Ball-Bearings/263381403327?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

Motor pulleys + belt - £9 https://www.amazon.co.uk/SODIAL-Tim..._1_15?keywords=gt2+16t&qid=1573399472&sr=8-15

coupler - £6 https://www.ebay.co.uk/itm/5x8-mm-M...hash=item56cc90ec79:m:mjzjICRI2be7jTjnsEWVzWA

Ribbon cable - £4.50 https://www.amazon.co.uk/gp/product/B07KJBJX6M/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1

Dupont connectors+tool - £20 https://www.ebay.co.uk/itm/Dupont-T...708100?hash=item2622450dc4:g:7nQAAOSwDV5dMegB

See if those links work, some things are discontinued already, like the ramps kit and the couplers but i added links to the same things, ramps about £1 dearer, coupler about £4 cheaper, because i ended up buying 4 when i only needed 1...

If anyone is interested i can maybe try figure out how to upload to thingiverse and add my tape measure cable chain parts as well.

Also just a little disclaimer, im not endorsing any of these parts, its just what i used personally, if you scout about you may find better or cheaper alternatives

 

[decca]

Cheers for that.
The RAMPS stack etc looks very complex to a non electronic person like me. Is it a matter of plugging it all together and hope it works.

 

[chrisg3103]

basically yes! The whole firmware flashing, messing about with arduino librarys, instaling drivers and whatnot can seem a bit complicated. But i managed to bumble my way through by tutorials and the step by step instructions on the v1 site.

This is the bits put together:

The arduino is underneath, its the brains of the operation and the red bit is a 'shield' that has all the relevant pins lined up ready to plug straight into the arduino. on the end is another shied that adds LCD sockets and the drivers are in the middle, only 3 fitted there but has the capacity for 5.

One the blue terminal block there you can see port D9 that i used to switch the relay for the plasma, forgot to add to the parts you need a 12V power supply, im just using a power brick as it will only ever be driving steppers, not hot ends and heated beds.

A messy overview of the guts of it

 

[decca]

Excellent. Thanks.

Looks really good.

I’ve started printing the parts today and will order the bits.

Great project.

 

[chrisg3103]

Good stuff, like i said those links are only a guide, feel free to shop about

What size you thinking on going? measuring up the working area of mine its turned out to be about 490 in Y and 470 X direction.

I have come to realise the past week that a portable CNC machine is just daft, its getting heavy and a bit delicate. So made this today:

Its still sort of portable had spare timber and the snazzy wheels were rescued from the works scrap bin a long time ago, come in handy one day, and they did!
It will be getting kitted out with a metal tray to catch the molten spray and i will be adding burning bars. It kind of negates the angle iron frame, i could of just screwed the legs to the trolley, but heyho

I am also looking into spindle and router options to use it as a multipurpose machine, quite fancy being able to engrave switch plates and control panels out of troply (think thats its name)
to use it as a router just add a plywood base to the top