In this build-along series we’ll take the Genuine Prusa i3 MK2 and clone it.
Follow along as we take a bunch of ridiculously cheap parts and try to make them work together.
The Prusa i3 MK2 is arguably a really decent printer.
But of course, when have to pay over 50 people’s salaries for providing support and for developing
the software and hardware, you can’t really sell the printer kits at the cost of just
the components themselves.
But thankfully, the entire design of the MK2 is open-source and still compatible with all
the other versions of the i3 design family.
So what I’m going to do is to create a low-cost MK2 clone, sourcing all the parts myself and
giving you a guide to use as reference if you want to build your own.
And actually, we’re going to go one step further and make this the cheapest possible
Prusa i3 MK2 ever built by entirely relying on import components and making a few changes
to the electronics and hardware that shouldn’t affect print quality, but will save of ton
of cash.
I think Prusa is going to hate me for this.
Now, the most interesting part is going to be how well the finished machine will perform.
I have two of the Original MK2s here, I love them to bits, and I’ll be able to benchmark
the clone we create here against the real deal.
Feature-wise I’m leaving out as little as possible: We’re still going with an all-metal
E3D v6 hotend, but obviously a fake version, we’re getting autoleveling with an inductive
sensor, but we’ll have to leave out the cool auto-squaring feature since you can’t
really buy the MK2’s PCB heated beds with the calibration spots yet, but we’re still
going with a decently sized regular heated bed.
Mechanically, the printer will be practically identical to the real deal, the changes I’m
making to cut cost is throwing out the fancy four-start trapezoid spindle for the Z-axis
and going with an M5 threaded rod instead.
This shouldn’t be much of a downgrade.
We’re still doing chromed and hardened rods with LM8UU bearings and NEMA17 motors with
the regular 2GT belt.
For the frame, I’m not quite sure yet if I’m going to go with MDF, plywood or aluminum,
but we will be making the frame ourselves, too, since that is often the most expensive
part in a low-cost printer unless you’re going with acrylic, which rarely is a great
option.
So that’s the basic concept, now what parts exactly are we going to need?
I’ll have a full list of components and links listed on my website at toms3d.org/dolly,
but let’s go through what we need and where I bought it.
Most of it is going to be Aliexpress, and I’m not listing fasteners here, those are
just going to be part of that full component list.
You’re usually best off buying those locally anyways.
So today we’ll start with the core 3D-printery bits and electronics, we need a hotend, an
extruder and a mainboard.
For a hotend, obviously, it’s going to be that fake E3D v6, you can get these with or
without the fan and fan shroud, and while we are not going to use the shroud, we do
need the fan, so we’re going with the full kit, which usually sells for less than five
bucks with the heater cartridge, thermistor and a 0.4mm nozzle.
You also need a bit of PTFE tube to guide the filament into the hotend, you might be
able to just ask the seller to throw in about 10cm for free, or just buy a 1m long bit of
2x4mm PTFE tube, which will cost you a whopping 80ct.
There are two different versions of the v6 here, one of them has been modified with a
Teflon liner in the heatbreak.
The original v6 doens’t need the liner since the surface inside the heatbreak has a much
better finish and won’t stick to your filament, and the genuine heatbreaks are also machined
thinner, which harder to do, but is essential to keeping heat from creeping up to the heatsink,
where, again, it will cause the filament to stick.
On good hotends, I’ve had more issues with these teflon liners than with the heatbreak
itself, but the machining finish on these knockoff hotends is often too poor to work
reliably, so if you can live with a maximum reasonable temperature of about 250°C, your
best bet is going to be a Teflon-lined version, which you can usually identify by the listing
being described as an “improved” type.
I personally went with the true all-metal version because I wanted to see how well it
works and, of course, have backup components in case it doesn’t.
For the extruder, we are going to need two specialty parts.
The drive gear and some springs.
For the drive gear, an MK8-style gear just about fits and costs around 80ct.
Most of the springs listed are a bit weak for my linking, but will work, I found a 10
pack of these 1.2mm wire diameter ones for a dollar and 20ct, and they are plenty stiff.
For electronics, I’ve looked around, but there doesn’t seem to be any cheaper option
than the ancient RAMPS 1.4 + Arduino Mega combo.
This is by no means a good electronics set, but hey, that’s not exactly what we’re
going for here.
It’s still going work well enough and if it doesn’t, we can make it work.
The RAMPS board itself sells for under $4, but you also need an Arduino Mega clone, typically
the Mega 2560 for around $8.
Also, four stepper drivers, we’re going with the standard A4988 boards here, and while
many of the cheaper boards have a lower current limit than the real deal from Pololu, that’s
not going to matter that much, if at all, and at 80ct per pop, you’re not wasting
much if you want to replace them down the road.
Though maybe get an extra one in case you fry one during setup.
I also grabbed a wiring set, which comes with pre-crimped wires for endstops, motors and
thermistors.
And it’s really worth those $3 when you don’t have to start messing with crimping
or soldering wires.
For the printbed, I’m using an aluminum heated one, since the cheap versions of the
common PCB heaters like to flex quite a bit when they heat and cool, which will randomly
shift your printed part up and down during a print, and, as you can imagine, that is
not the best thing to have happen.
This one for $6 didn’t include a thermistor, but you can get a pre-wired one for 50ct.
These aluminum beds aren’t always titled explicitly as an aluminum bed, but the effort
of digging through a few offers is definitely worth it.
Now, the smaller electrical parts for the builds are a 50 by 15mm radial fan for part
cooling, I picked this “low noisy” type, an inductive sensor to use as a Z-axis probe,
and you can get a type very similar to the one that Prusa uses now, running directly
from 5V and making any sort of voltage adjustment circuitry unnecessary.
You’ll also need endstops, the easiest option is definitely going with these complete sets
with the switch, a connector and some smoothing circuitry on a PCB at about 70ct for a pair,
which also includes a cable.
And the last big part for electronics is the power supply, the Original Prusa uses a 12V,
20A type, and while pretty much all these parts could handle 24V and would probably
run better with those 24V, 12V supplies are still cheaper and more easily available.
For getting one, I’d actually recommend checking resellers in your country first,
they might actually be cheaper than ordering directly from far-east sellers since these
power supplies are comparatively bulky and heavy and sellers sending them directly to
you from China or HongKong will have to pay quite a bit for shipping.
Finding the exact supply used the Original MK2 is going to be hard as it looks most sellers
have switched to a different, smaller model, which looks like it got rid of the mounting
threads in the side, but it should work nonetheless and at about $15, it’s practically the same
price as the old one.
If you want to be fancy, you can add a fused IEC socket and a switch to the power supply
shroud, but since those are quite expensive at $2 and will need some soldered or crimped
connectors, I’ll leave that choice up to you.
You can definitely run a power cord directly into the supply as well, the supplies are
fused and protected on their own, anyways.
And that should have the electronic parts pretty much covered for now.
Of course, you’re free to add an LCD controller to the setup, we will actually configure the
firmware to work with or without the LCD.
You can go with either the larger pixel-based displays for around $10 or the faster, but
smaller character-based ones for a bit under $8.
I’ll be making a firmware configuration for either one, just make sure you get one
that does include the adapter for the RAMPS.
You might also be able to find package deals with the Arduino clone, a RAMPS, drivers,
endstops, wires and the LCD, but they’re not always cheaper than buying everything
individually and hunting for the best price for each component.
So let’s check out what we have: We’ve got all the specialty parts for the printhead,
so the extruder, hotend, fans and bed sensor, we’ve got a mainboard, stepper drivers,
the Arduino, endstops and wires.
And we’ve also got a heated bed and a beefy power supply to go along with that.
Total cost so far: $53.06, including shipping, but you might need to factor in import fees
and taxes, but these smaller parts are usually free.
Again, all these parts are listed at toms3d.org/dolly including links and all.
Next week we’re going to start looking at mechanics, but I did want to get the bulk
of these smaller components covered now since these parts will take a bit to arrive at your
doorstep.
For me here in Germany, it’s anywhere between 2 and 8 weeks from ordering to delivery, and
depending on where in the world you live, it might be a bit more or less.
You can also order the exact same parts from local resellers, for example on ebay, to get
your stuff faster, but you should anticipate paying about two times more.
Or, of course, you could get some locally available quality parts, but that’s not
exactly the point of this build.
Waiting on parts from China does give us a bit of time to work on the frame and mechanics,
though.
I think I’m actually going to go with a wooden frame, since that should be the cheapest
option, but let me know if you’ve got other ideas.
Of course, stay tuned for the next part, but if this video helped you out in some way or
another, give the video a thumbs up, if not, leave a comment on how I can improve.
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And that’s it for today, thanks for watching, and I’ll see you in the next one.