Building the MPCNC: Parts and component choices!


It is time. We’re building the MPCNC!
I actually had one more video planned to go up before I started on this build, but Adobe
just didn’t want that to happen. So… we’re going to live-build the MPCNC
together, like with Dolly, the Prusa MK2, uh, clone, but unlike that, this one is going
to be the real deal. A full MPCNC in the burly version, which is the current, sturdier design
variant. In this video I just want to go over the parts I’m using, why I’m using them
and what alternatives there are. But first, what even is the MPCNC?
As a full explainer, check out my interview with the MPCNC’s designer from MRRF 2018
up here, but basically, this is a closed-source, 3D-printable, where it makes sense, CNC router,
engraver, let’s just call it a light-duty CNC. The base is any sheet of flat material
you want to use, the frame and linear rails is steel tubing, if you have it available,
you can use electrical conduit, the motion is done with just 6mm GT2 belts and NEMA17
motors and a 3D printer control board, any board you have will basically work. And of
course, there’s a toolhead, I’m using a spindle, but you can of course also use
a 3D printing head with an extruder and hotend or a pen plotter, drag knife, paste extruder,
whatever you want. The nice thing is that you can easily scale the machine by using
a larger base and longer tubing and belts. I’m building mine with roughly a 50x50cm
build area and 15 or 20 centimeters of vertical travel. I’m not exactly sure how large the
actual usable build area is going to be once you add fixtures, the tool and so on, but
it should be comfortably large in either case. So looking at these parts, it should be obvious
that this is not a machine that will be massively rigid and end up cutting stainless steel or
titanium, at best, I’m hoping for some drilling and light cutting in aluminum, but I think
this machine is much more comfortable cutting or engraving wood, plastic, foams, those sort
of softer materials. So, parts, let’s start with the printed
parts. These were printed from simple PLA, which is rigid and strong, exactly what you
want out of a CNC frame. Unlike the topology optimized shelves, there are screw heads pressing
against the parts and potentially hot components touching the prints, so I’ll have to see
how well it holds up. These parts were printed on a bunch of different printers with a bunch
of different PLAs and, I don’t know, the color scheme is definitely… disagreeable.
Overall, this is one and a half kg of filament, two small spools, so it’s quite a bit of
material, but these parts are designed quite chunky, so you don’t need to use your fanciest
filament for this. In fact, I used up random bits of old PLA that I had hanging around,
so excuse the color scheme. The set of parts is the Burly set from V1
engineering, and I’ve also printed a mount for my spindle, I believe off thingiverse.
There’s a healthy ecosystem of modified parts available already.
And speaking of the spindle, calling this thing a spindle maybe is a bit much, but that’s
what the seller is calling it. I’ve used a similar one in the Mendel Max CNC conversion,
but this is a brushless version of that “motor with a chuck” assembly. I’m hoping that
the controller might be a bit smarter and give consistent torque over the RPM range.
For the brushed version, the only sort of RPM control is by adjusting the power supply
voltage, but this one has a special power supply included in the kit that not only lets
you adjust RPM, but also has a digital readout that displays RPM in real-time, and I think
that’s a huge deal when it comes to tuning in cutting parameters, it just takes the guesswork
out. The alternative is using a trim router as I’ve got in Bob, the Sienci CNC, but
I find that to be one of the worst options, as they tend to be super noisy and in my case,
getting collets for the thing turned out to be an absolute nightmare, so I could only
really use 6mm shaft endmills, which is actually really large for how rigid these small machines
are. These smaller motors just have an ER11 collet chuck, and the collets for those are
incredibly cheap and available everywhere. It’s just a standard size.
Next up, the frame. For the base, I used this piece of particle board that I glues some
MDF to, I like the smooth and flat surface of MDF, you could probably use just a thicker
piece of MDF, or plywood, really, as long as it’s flat and you can screw things to
it, you should be fine. You could probably even use a T-slot table, that way you’d
directly have a way of clamping down parts. These tubes doubles up as both the frame and
the linear rails, so it’s a really good idea to use something that’s fairly rigid.
The MPCNC files are available for 23.5, 25 and 25.4mm aka 1” tubing, which I believe
may be fairly common in the greatest country of the world, but for me, I could really only
get hold of 25mm tubing, this really is just standard tubing stock, I ended up using this
ground stainless version, which is more expensive than conduit would be, but not unreasonably
pricey by any means. The sizes that would be really easily available here would be for
things like galvanized water pipe, which comes in nominal ½” and ¾”, which actually
is 21.3 and 26.9mm on the outside. Don’t ask me how those sizes make sense, but maybe
we’ll see an MPCNC version that supports one of those sizes at some point.
Now, for the motion system, I grabbed some random NEMA17s, as well as a fresh roll of
GT2-2M 6mm glass fiber belt, the same stuff that’s being used on 3D printers; interestingly,
V1 say that you should not use this steel-reinforced belt, so I’m not doing that.
For electronics, I’m using the Duet Wifi – for now. It has strong drivers and great
software, but I may swap it out for something simpler at some point as I might need the
Duet back in my Mendel9000 test platform which, yes, is finally printing. It should be an
easy configuration swap moving the board between machines.
So one last thing you need is a bunch of fasteners. You can use both metric or imperial sized
hardware, but the parts are designed with imperial parts in mind as far as I’m aware.
Oh, and you do need a leadscrew and a coupler and pulleys and cables, but that’s really
unexciting stuff that you kinda need for every build. The same goes for tools, you need a
few basic things like hex keys and maybe a few spanner for some nuts, and I believe you
also need a way to drill a few holes into these tubes for the Z-axis. But, for example,
the base, you can get cut at pretty much any home center in any size.
Now, you can buy all these parts, minus the tubing, and I think the base, directly from
V1 engineering, but of course, there’s also the option to self-source, which I tried,
and I ended up a bit cheaper than what the kit would have cost. Of course, which option
is better for you depends on where you live and what your preferences are in self-sourcing
vs. buying a kit, but just like with Dolly, I’ve created a full list of parts over on
toms3d.org with options of where to get each part.
So over the next days, I’ll be building this MPCNC together with all of you in a series
of livestreams, the first one will start tomorrow on Sunday, August 25th 2019, so if you’re
free, come join in and maybe even build along, the link is in the description so that you
can enable that notification,but these streams will also be available as recordings for your
enjoyment. The great thing is, you can skip forward in recordings!
So I hope to see you there! As always, thank you for watching, leave the video a like,
get subscribed or even support the channel through YouTube memberships or Patreon, and
I’ll see you then! Bye!

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