The most important 3D printer – Original Prusa i3 MK3 review!

The most important 3D printer - Original Prusa i3 MK3 review!

The Original Prusa MK3 might well be the most impactful 3D printer on the market right now -- but is it also the best?

Well, how do you review this thing? There’s nothing that I could fully compare the Original Josef Prusa i3 MK3 to, I mean, it’s doing so many things that no 3D printer has done, at least not at this scale. Like, it’s a really good printer now, and it’s also not just “yet another i3”. So I don’t know, let’s just go through it step by step and see where all the many aspects of the MK3 fit.


Open Source

Ok, first things first: This thing doesn’t look all too different from the older MK2 on the surface, or even different from many other i3 printers. Why is that design so popular in the first place? Because it’s open-source! Prusa has always published all the design files for his machines, including the very first i3 that spawned thousands of derivative printers, and that hasn’t changed now that it’s not just Jo Prusa himself anymore, but literally a factory full of employees making 3D printers all day.

So yes, everything on this printer, starting from the frame, which of course is still just a metal frame, to the electronics and sensor boards down to the firmware and the improved slicer, all that is, right now, published on Github, under an open source license, and available for any person or company to make use of or modify for their own products or projects. And that is just fantastic. Now, I wouldn’t care about this half as much if the MK3 was just another 3D printer, but for this one, it’s incredibly important and we’ll get back to that in a minute.

What is new with the MK3

What is new with the MK3, because the open source topic, that’s old news, at least for Prusa. In many ways, you could say this an evolution of the i3 MK2 and the entire i3 and RepRap Mendel family before it. Let’s start from the bottom: It’s still the same basic frame and motion layout, but it’s not using the dreaded threaded rod sub-frame anymore, but simple machine profiles that come pre-cut and just need to be screwed together for a square, and actually surprisingly rigid frame. On the bottom, it has the push-in rubber feet, which are nice and soft, but they fall out so easily every time I try to move the printer, I really wish these were screwed in. That might be a nice printable upgrade, actually.

The bed is now a two-part setup, with the print surface as a separate part from the heater PCB, and those two are being held together magnetically. There’s a ton of neodymium magnets embedded in the underside of the heater PCB, and I’ve got to say, they hold down the bed like crazy. You definitely don’t want to get your fingertips pinched in there when it snaps down. The print surfaces are these spring steel sheets, and while the early MK3s were shipped with the basic same setup as the MK2 with just a PEI surface taped to the spring steel, and that setup is somewhat delicate, but works and sticks well, what’s actually supposed to come with the MK3 is this thing. This is basically PEI powder-coated directly onto the spring steel, and I’ve got to say, this is the absolute killer features of the MK3. If I, for myself, got to choose one single improvement over the MK2 that I got to use, this would be it. This is a really big deal. When a print is done, you take out the spring steel, bend it a bit and the part just pops straight off. You can clean or prepare it with additional adhesives outside the printer and it’s really easy to replace should you ever need to, or you can just use the backside. Same print surface on there! There are some other printers that make use of this concept as well, or you can add it to your own machine this size with an upgrade from Buildtak that runs 120€ on its own, but I’ve not seen this textured surface anywhere else yet. I actually really like it, because it’s a bigger surface area for your print to grab onto, it makes first layer height a bit less fussy, and, this is the big one, the texture matches up with the natural layer texture you have on your prints. So it’s not this alien surface on there anymore that’s all shiny when the rest of the print is textured. The surface is much more robust than taped PEI and since you’re not going in there with a knife or spatula, you know, this thing is just going to last. You can even get away with printing some materials that will typically destroy a PEI bed, like PETG, if you get the print temperatures right.

Ok, I am excited about the bed and I assume I got that point across pretty well. But that’s not the only thing that’s new here.

So, 3D printers typically are pretty dumb. They do what they are told even if it means they’ll destroy themselves in the process. Now, if you intentionally tried, you could still get the MK3 to destroy itself, but it’s making it really, really hard for you. This is the smartest dumb printer out there right now. So, it knows:

How hard each axis runs and it can deduce how tight your belts are from that

Whether you’ve built the frame square and it can actually auto-correct for that and leveling issues

It knows whether the two independent Z-axis spindles are out of sync

It knows How warm your ambient temperatures is and how hot the electronics are getting, so it knows not to immediately trigger the mintemp error if you’re actually printing in a colder environment and it even knows whether, on the mainboard, you’ve tightened down the heated bed wiring enough so that the screw connectors make good contact with the wires

It knows when a motor is skipping a step when it’s running into a print that’s curling up

It detects when you’re having a power outage, moves the hotend away from the print and then just keeps on printing like nothing happened, so Prusa actually had to include counters for that in the firmware because nobody ever noticed it

It knows when the extruder is slipping because the spool has tangled or is simply out of filament, and it uses the same sensor so that you can just push in new filament and the printer will automatically load it

It monitors the two fans on the toolhead, so when one fails or gets jammed by a bit plastic floating around, it can keep the fan from burning, and save your hotend and the print

It even knows when you’ve pulled out the SD card from your computer without safely removing it -- yes, that can actually corrupt your gcode print files and I’ve had that happen on other machines before where the printer just stops in the middle of a print, and the MK3 just won’t let you print those files


And this sort of stuff, this is exactly what I’ve been wanting 3D printing to evolve towards because that’s the feature set that will actually make 3D printers a much less frustrating experience for everyone. Again, there were other, even commercial 3D printers that did some of these things years ago, but it didn’t catch on because they didn’t release any source files or even just information on how they pulled it off. So to a point, I actually don’t care whether the Original Prusa MK3 is a good 3D printer otherwise or not, because even if it would completely flop, the knowledge is now out there for everyone to make use of and I fully expect some of this stuff in here to become standard for every 3D printer one or two generations from this. And that’s something that’s good for everyone.

How the MK3 performs

So does it suck as a 3D printer? Naw. Didn’t really expect anything else. The MK2 was already praised for its print quality and reliability and the MK3 just puts another cherry on top. So what I’m actually seeing is de facto better print quality than anything else. A big and really obvious part here is the Trinamic drivers. To the left here, you see the MK2’s output, to the right the MK3’s, and the difference in how well microstepping works is pretty obvious. The MK2’s microstepping performance was ok, but this now, this is flawless. The new part cooling fan shroud has also been improved because it reaches around the hotend more -- with the MK2 and many other one-sided cooling setups, in some edge cases you’d see more curling and overheating artifacts on one side of some PLA prints, this one -- flawless. You’re now getting Bondtech drive gears in the extruder, so that’s two hardened steel gears that grip and drive the filament from both sides, if those ever slip, there’s something seriously wrong, so long story short: These don’t slip.


Oh, and did I mention how quiet the MK3 is? Oh, you couldn’t hear that there was one right here, printing the entire video so far? Yeah, that’s how quiet it is. It is crazy quiet. I’ve walked into this room quite a few times now and thought, yeah, cool, the print is done, but I just didn’t hear that it was still printing. It is fascinating. It can run the TMC2130 stepper drivers both in SpreadCycle and in StealthChop, and you can choose whether you want the skipped steps detection or even quieter printing, and this is how it stacks up against some other printers:

  • Prusa Mk3 53dB(A)
  • Ultimaker 3 50dB(A)
  • Printrbot Play 56dB(A)
  • Atom 3D 2.5EX 54dB(A)
  • Prusa Mk3 Normal 40dB(A)
  • Prusa Mk3 Silent 38dB(A)

The hotend cooling fan now is actually a super-quiet 5V, 40mm Noctua fan, and it’s still one of the noisiest bits on the printer. Stuff like an idler pulley slightly squeaking, you just couldn’t hear before.


So far, this all sounds really good right? But to be honest, I was actually struggling quite a bit on what my opinion should be on this very 3D printer, because let’s face it: The launch was somewhat of a mess. Granted, Prusa is hiring people as fast as he can find them, and the amount of printers they are putting out now is crazy, but I guess there were still too many orders coming in for Prusa Research to ship all of them perfectly on time. The early buyers were given the option of either getting their MK3 now, with an adhered PEI bed, basically the same stuff that shipped with the MK2, and they’d also get a discount if they wanted to upgrade to the coated bed later on, or the other option was waiting a bit longer and getting it exactly as they ordered it, with the coated bed right away. As it turns out, these beds are a bit harder to manufacture at a decent quality than they expected.

Also, all the cool sensor stuff didn’t really work when I first tried it on my machines.

On top of that, Prusa somehow managed to ship me an assembled, but refurbished development unit, so even though it went through the usual functionality tests, apparently some of the electronics were still prototypes that were still being tweaked and are improved in the final version now, and also, it didn’t go through the “normal” assembly process, so it even came with a few loose screws. The kit version was much better out of the box and while I was testing the MK3s, Prusa was releasing updated firmwares, like twice a week. Still, it felt like beta testing and I did run into some pretty fundamental bugs, and you just don’t want that as an excited user who’s one of the first ones who’s getting the shiny new MK3. There’s a reason why I don’t like doing beta testing, and this is it.

Good news, though, as of right now, we’ve got firmware 3.1.1 and everything now works as expected, I’ve put the full set of smart features to the test many times and everything works well, every time, on both printers, so that’s good.

Now, I’ve not experienced the MK2’s launch first hand, so I don’t know how Prusa’s track record stands for product launches, but I would expect them to at least learn from it for next time.


Alright, back to the MK3. We touched on print quality, we touched on some of the features, let’s touch something else!

Oooh, look at that! It’s an assembly manual! And a full user guide to 3D printing. That’s quite something! An assembly manual that’s this detailed apparently can’t be taken for granted these days, especially one that actually takes you all the way to an assembled printer, and then the handbook takes over, giving you the basics on software installation, material selection, tuning, maintenance, debugging, there’s quite a lot of information in here, and even if you have no outside help, this should get you going with a good bit of knowledge on 3D printing in general. But you do actually have to read it.

The MK2 came with a very similar guide, but what it didn’t come with was this new spoolholder, which now works with almost every type of spool, and it also didn’t come as a 24V system, which means lower currents and more efficient power handling in the printer. Also, faster heatup and slightly higher maximum temperatures on the heated bed. That’s never a bad thing!

The new electronics, the Einsy board, now built with 24V in mind and using the Trinamic drivers on board, are still manufactured by Ultimachine, it’s still open source, and you can actually buy it by itself from Ultimachine directly. It’s also still an ancient 8-bit microcontroller controlling the entire thing, but looking at what the developers at Prusa are managing to pull off with just this puny chip really makes me think whether we actually need the 32bit platforms for performance alone. The MK3 does print slightly faster than the MK2 and this board is not limiting printer performance in any conceivable way, but I do think the next generation needs to be a 32bit platform, even if it’s just for integrating some sort of network functionality. Right now, you can plug in a Raspberry Pi Zero and use that for OctoPrint, but I’m sure there are better solutions out there. If you want more detail on the Einsy board, you can watch the interview I did with Jo Prusa at TCT right here.


Is the Mk3 worth your money?

So should you buy the MK3? If you want a solid, smart, open-source machine, yes. With all the updates it’s gotten in its short life so far, it’s turned into a reliable machine that’s actually really enjoyable to use. You don’t need to do any tuning or anything to get printing because the included slicer profiles do everything for you, it’s overall just a really painless experience. But what about the MK2S, you ask?

So the MK3 sells for currently 749USD as a kit or 999 assembled, so it’s a bit more expensive than the MK2 was at launch, but it’s also much more printer. But when the MK3 launched, the MK2S, so the slightly improved version of the MK2, was also dropped in price to now 599USD or 899 assembled. For the assembled one, I think you should just go for the MK3, but as a kit, the MK2S, even if it is a bit less flashy, I think is still a solid choice. I’m still using the MK2s a ton, I don’t think I’ve ever had an issue with them even after thousands of hours of printing, of course other than stuff that was completely my fault. So if you’re ok with the MK2S being louder and not having the flex bed, and if you don’t think you’ll make use of the smartness, then the MK2S is still a great workhorse to get.

Still, MK3, highly recommended, and I’m really looking forward to everything this printer does / becoming standard everywhere.


So I hope this review was helpful to you, if you want to get any of the MK3 or MK2 printers, you can find the links in the video description below. Those are affiliate links, so buying something through them helps fund the channel. I mean, I would be better off just recommending the CR-10 on Gearbest instead, the affiliate commission on that is actually a good bit better, but that’s just not how I do reviews.

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As always, thank you for watching, and I’ll see you in the next one!

🛒 Prusa MK3 Kit Here
🛒 Prusa MK3 Assembled Here
🛒 Buildtak flex plate Here


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