Original Prusa MK4 3D Printer Review: The Quiet Workhorse

Prusa MK4 (photo credit: Prusa)

On March 29, 2023, the Original Prusa™ MK4 release announcement put the consumer 3D printing industry on notice: Prusa is Back! With its improved extruder, input shaping, cell sensor, and many other features, it promised “perfect first layer every time” and was said to (with then-unreleased software) print the canonical Benchy benchmark in under 20 minutes, while keeping the sound level below that of everyday speech. A fine upgrade from the five-year-old MK3 design, this is.

Prusa is (as far as I know) the only consumer-priced 3D printer maker in the world that doesn’t manufacture in China; their printers are made in Europe, without state benefits (tax breaks) to undermine the west, and with fair labor laws and such. So naturally Prusa printers cost more. The Prusa company is also one (not the only one) of the main sources of innovation in 3D printing, and since Josef Prusa is a strong believer in open source, most of their innovations get copied by the copycats. In fact, the term “Original Prusa” is a trademark, to provide a layer of reputational clarity. PrusaSlicer, an offshoot of the original “Slic3r” which adds many features, remains open source, and fully supports the MK4 (and most other makers’ printers, and Prusa’s filaments and those of most other manufacturers). PrusaSlicer has been adopted by several other printer makers, leading to offshoots like Bambu Studio, SuperSlicer, AnycubicSlicer, OrcaSlicer, and more. In the other direction, the original version of the “Marlin” firmware that runs in the printer is open source that Prusa uses, though heavily modified. Prusa also funds https://printables.com, a widely-used repository of freely-downloadable models. (Thingiverse, an earlier models repository, is similarly funded by printer vendor Ultimaker).

I must admit that I actually vacillated for some time after this printer’s release, looking at:

• This, the Original Prusa MK4;
• The low-cost Sovol SV06 Plus;
• The Bambu Labs P1P;
• Although it was released at the end of my deliberations, the Creality K1.

The quartet above are all in competition and are probably the start of a new “arms race” (robotic race?) over speed and price-performance. All four companies are well-enough established and funded that they’re likely to endure.

The first two printers are traditional “bed slinger” designs, where the bed is fixed at the same height and moves in the Y plane (front to back), and the printhead moves in X (side to side) and Z (up and down). The latter two are “CoreXY” printers, where the bed moves up and down and the printhead moves in the x and y planes. Prusa also has a CoreXY design, the Original Prusa XL, but it is significantly more expensive than the MK4.

Like most other manufacturers, Prusa also makes a resin-based printer, but I’m only looking at FDM or filament-based printing here.

Why Prusa? Some factors that tipped me to the MK4:

• I guess I’ve always wanted a Prusa;
• the MK4 feature set;
• the fact that it’s made in Europe, where fair pay for fair and safe work is required;
• the massive installed base of customers of previous similar models who can help in online forums;
• the reputation of their customer service;
• and the color orange :-).

In fact, I had just purchased a Sovol SV06+ when the MK4 was announced; I wound up passing the Sovol along, unopened, to another purchaser. It did try my patience to avoid ripping it open and trying it out, but in the end the Prusa-on-order won out.

The MK4 (officially pronounced “Mark Four”, not “em kay four”) can, like all Prusa printers, be had either in kit form or assembled & tested. Assembling the kit will teach you a great deal about how the printer actually works, as you put the pieces into place. But it will take most of a day. Despite the higher cost, I went for the assembled version, as I’ve already built a couple of 3D printers (both of which worked, neither 100% satisfactorily), and wanted something that would be more likely to “just work” out of the box.

At the beginning of the announcement, the web site erroneously claimed there was a 6–7 week backlog. In Prusa Live #51, right after the MK4 announcement, Josef said this was quite wrong and blamed it on their CRM software. But it turns out there were so many orders that it was in fact correct by the time I got my order in on April 18, 2023. I was a bit disappointed that no shipping backlog estimate was provided upon ordering, and some days went by before I heard anything other than “we have your money.” Speaking of money, their European credit card billing provider was unable to process my Canadian credit card for some reason. I tried several times and eventually switched to PayPal.

In fact, one of my biggest pain points was the lack of information on the order queue. If you have an order for a roll of Prusament filament or a spare print sheet, your order will show the expected ship date. But order a US$1100 printer and…​ at the time I ordered, you’d get no feedback on when your order is likely to ship. This matters as the “5–7 week” backlog was stretching into the summer, when people may be away on vacation and unable to receive their orders (porch piracy anyone?). I was starting to line up a friend to receive it, in case it arrived when I was away. But in the end it arrived the day before I left on vacation, so didn’t get unboxed until my return. This queue has since been cleared, but their IT needs a shakeup so this doesn’t happen all over again when the MK5 is announced.

Feature Set

Just to be sure I don’t miss anything, here is the list of features, quoted directly from prusa3d.com:

• “The successor to the award-winning 3D printing workhorse Original Prusa MK3
• “Effortlessly fast and silent 3D printing. Check out the sub-20 minutes Benchy video on MK4!
• “Fully automatic first layer calibration thanks to the Load Cell sensor
• “Print right out of the box — no print sheets profiles, no tinkering, no Live Adjust Z!
• “Nextruder — our new extruder with a custom breakout board and smart features
• “Safety features like filament sensor and power panic that won’t let you down
• “Easy maintenance, quick-swap nozzles, and removable print sheets
• “Support for a wide range of materials, including PLA, PETG, Flex, Nylon, ASA, PVA, PC, PP, composites and more
• “Color LCD screen with simple-to-navigate UI and quick access to all important functions
• “Ethernet and Wi-fi connection
• “Made in the EU, hassle-free warranty, 24/7 live chat support
• “Open-source”

Some buzz on the internet says that the MK4’s release was “rushed” due to pressure from the recent announcements by competitors listed above. That is belied by the fact that Prusa has had their in-house MK4s running for over one million hours over the last year. If you do the math, you’ll see that that means they presumably had over a hundred MK4 units running 24/7 for a year, or 200 for half a year, etc., all the while churning out test prints and parts for printers. It is impressive that there were no leaks before the official announcement!

That said, the “sub-20 minute Benchy” is based on software that was released after the initial orders shipped, and running in “draft” (lowest resolution) mode.

The LCD screen is a big improvement over the MK3’s. It’s color, and higher resolution. This is used to advantage when a major error occurs (see image, a transient error that only occurred once, and that during initial shakedown). The screen hardware does have touch support but the software doesn’t take advantage of that yet (it arguably doesn’t need to, as the UI is simple enough with the single control knob) [Edit: a touch UI works as of 6.0, released starting in April, 2024]. The front panel is rounded out with a reset button and a USB-A socket for the unit’s only user-accessible disk storage.

LED in normal use

LED on error (note QR code) — Rare, but stuff happens

First Print

Since the non-kit version of the printer arrives fully assembled, the initialization consists of opening the box, moving the printer to a stable table, removing some foam packaging, plugging the printer in and turning it on, running a simple self-test, and printing. At least in theory…​ Well, no. In practice too. Load filament and a model. Press Print. It just works.

My first few prints worked fine. That perfect first layer does appear. Then I wanted to try something harder, and will discuss that in a bit. First, let’s get print files to the printer and look at nozzles.

Software: It slices, it dices…​

You probably know that 3D models have to be “sliced” to generate the low-level machine-language (“g-code”), which tells the printer where to move, when to feed filament, what temperature to use on the head and the bed, and more, for each layer or “slice”. PrusaSlicer is Prusa’s own slicer software. It’s heavily re-written from an earlier tool called “Slic3r” by Alessandro Ranellucci. PrusaSlicer™ can be downloaded for Linux, Windows and Mac from its own web site. Known as a software contrarian, I run OpenBSD Unix on my laptop. So I got involved in “porting” PrusaSlicer to OpenBSD, which was done in October/November 2023 (much of the work done by Renato Aguiar and Johannes Thyssen Tishman). I do have a Mac in here somewhere for the odd job that needs it.

PrusaSlicer is a full-featured slicer which can:

• import a variety of file types (including STL, OBJ, 3MF and STEP);
• generate g-code files for a wide variety of printers, not just Prusa’s;
• provide the best parameters for a wide variety of filaments, not just Prusament.

PrusaSlicer is updated regularly. The sofware in the printer itself — the “firmware” — is also frequently updated. My printer arrived with some version of 4.9, and got one 4.9 update soon after it arrived. Version 5 provided some of the features that were promised “for later” at the time of the initial offering. The latest version as I write is 5.1, which includes a means of compressing gcode for those loading it over slow links. For better or for worse, it also compresses the thumbnail images that are used on the printer to show what you’re printing (helps to be sure you’re printing the right file!). Since the prior firmwares did not understand this compressed format, this upgrade requires changing the firmware and PrusaSlicer versions at the same time if you want to see the previews. I have been able to print files sliced with PrusaSlicer 2.6 on firmware 5.1, though the thumbnails appear on screen as gibberish.

Connectivity

The printer supports wired Ethernet, wireless (WiFi), and insertion of USB drives. Since I prefer wired, I only used Ethernet and “sneakernet” — moving files by walking USB drives from computer to printer. As a result, I’ve not been troubled by the “slow WiFi” problem that others have reported.

PrusaLink is a web-based program for locally managing a single printer. Works with any modern browser. It lets you upload files to the printer, start them printing, monitor the print job, and download or remove files from the printer’s USB storage. It works nicely in my experience.

One annoyance with PrusaLink is the web-based login; it requires the username be “maker” and the password be some random gibberish generated by the printer, and which can be displayed on the printer’s LCD screen. There’s no option to let you provide your own password, so the all-too-common “abc.123” will not get you in. On the one time PrusaLink got confused and couldn’t talk to the printer (probably a DHCP issue, i.e., problem at my end), I simply fell back to USB.

PrusaConnect is their cloud-based connection service. I’m in the minority here but I am not a fan of cloud-based storage for my models, so I have not tested it. With the latest softwares, it does offer two benefits, streaming download, and OTA firmware updates. The steaming download feature is a response to slow network throughput. Before this, you’d have to wait for the entire file to download to the printer; for large files on a busy print farm, these delays cost money. Now, as soon as it’s received the first few g-code instructions, the printer can begin working. OTA (Over The Air) firmware updates have been a thing for a decade on smartphones and Tesla cars, so it’s only natural for them to arrive here. Since I don’t use PrusaConnect, and PrusaLink won’t send firmware files, I have to transport the firmware the few feet from my computer to my printer on a USB memory device. Every few months, I can live with that.

To illustrate my dread of the cloud, in addition to the possibility of, say, Bambu Labs letting the Chinese government in on my latest designs, consider this: Bambu Labs takes the cloud approach further, to allow starting a print job completely hands-off. Unfortunately for them (and their customers), a glitch in their cloud software caused many of their customers’ printers around the world to start printing unbidden, even when the print bed contained a previous model, causing some printers to get broken, and repairs needing to be done, either DIY or at the factory. Not a brilliant start for a young company!

OctoPrint is a third-party open-source program for running your printer, developed by Gina Häußge since 2012, and community funded. It’s available pre-configured to run on a Raspberry PI, in which version it’s known as OctoPi. Has the same capabilities as PrusaLink, but much more. It has a large number of plug-ins, and supports the use of the Raspberry PI camera. I used it on a previous printer, but haven’t set it up with the MK4. Others have done so.

Nextruder

The “load cell bed leveling” is such a fantastic feature that everybody’s copying it, except for Bambu’s higher-end unit which uses LIDAR for the same effect. It actually touches the nozzle very lightly to the build plate, so it knows exactly what the bed height is at each of a bunch of spots. And it only does this in the part of the print bed that will actually be used — a timesaver for most prints. On many less-expensive printers, when you change the nozzle or the build sheet you have to re-calibrate the Z height over the entire bed. The MK4 handles this chore automatically. This is a big win! You can see videos on Youtube where people cut out a piece of a corrugated cardboard box, or a thin piece of wood, and taped it onto the build plate. The Prusa MK4 happily printed right on it — without needing any adjustment.

You can change the nozzle in a few tens of seconds if you have the right parts; one side of the print head box is a fan which is hinged to open and let you at the innards.

More Challenging Prints

Of course the real test of a 3D printer isn’t just how well it prints the first week, but how well it continues to print after a year or years of use. The various MK3 family was described as a “workhorse”, and it certainly fits that. People have had them running successfully for years. The MK4 is a follow-on design that has been well-tested with some in-house units running flat out for a year.

I printed a number of copies of the “cat key holder” for friends and relatives. The ones printed with Canadian-made EconoFil PLA were successful. A few printed with Prusa’s own Prusament PLA ran into errors; several failed to print the “hook” on the bottom of the lever that opens the box, and one had a rough spot that caused the top to stay open when it shouldn’t. Experienced 3D print makers know that there are wide variations among different filaments, so this wasn’t a great surprise. As well, this is a “print in place” design. This means that moving parts don’t have to be assembled; the lever is printed pre-mounted on its shaft, so less assembly is required, but it has to “broken loose”. There is a somewhat greater chance of failure, and it’s impossible to rectify certain printing issues without re-printing the entire box. Nonetheless, I made a series of cat key hooks that work, and gave them around.

Cat Key Hook

This Dice tower from Thingiverse.com was my next project, a gift for some gamer friends. Dice towers have been used since around 400 A.D. to ensure a fair roll of the die or dice. The PrusaSlicer program said that this project would need “supports” to print properly. FDM printing works by laying down successive layers. Supports are needed when a layer overhangs the previous one by more than 45 degrees, or when part of the print sticks out over air. But the tower’s designer, Shin da Silva aka FresnelTHz, says “no supports”. I took the designer’s word for it, and the tower printed perfectly in PLA.

Dice Tower

As a further test/demo, I chose to print the Grand Castle. A well-known 3D print, this is a cloud-based “Thingiverse Customizer” that let you choose how big to make your medieval castle, how many towers, how much randomness in the design, etc. You can also download the model files to run locally in OpenSCAD, one of several free open-source modelling design tools. I regard the Grand Castle as a good test of a 3d printer because it involves a lot of hopping from tower to tower, and will highlight the printer’s ability to position itself quickly and accurately, and the filament’s resistance to “stringing”, tiny shreds of filament left behind as the printer moves. I picked a small size with a few random towers. It printed in about 2.5 hours using “0.30mm Draft” mode, and had a little bit of stringing, the latter probably because I didn’t dry the filament and my basement office is relatively humid. Stringing is easy to remove “in post” just by using a hot-air gun or a hair dryer.

Grand Castle, printed in draft mode with minor stringing due to non-dried filament

I have had a few print failures, but I think most of them are due to operator error — failing to dry the filament, not cleaning the build plate often enough, and such like.

Powerful PowerFail Recovery

The MK4 saves its state constantly, so that if the power goes out, it can resume from where it left off. Most reviewers have to pull the plug out of the wall to test this feature, but I live out in the country, where power glitches are a bit more common. So I got to test this feature “for free” when the lights went out while I was printing parts for my printer’s DeLack Enclosure (see below). With the lights back on, the machine picked up right where it left off. There’s a slight line visible as a “souvenir” of this event, and a bit of extra filament got extruded, which was easy to peel off. The important part is that there was no layer shifting or other significant damage.

Extra Options

The “Nextruder” extruder uses Prusa’s own nozzles, which can be purchased from them, in a few diameters. Since people don’t want to be tied to one supplier, Prusa came out with an “E6 nozzle adapter” which lets one use the more widely available (and less expensive) “E6”-style nozzles. Also, you can get hardened steel nozzles in E6 style, but not yet in Nextruder format. The adapter wasn’t available on day one but has been available for months now.

The longest-delayed promise for the MK4 was the MMU3, the third iteration of the “Multi Material Upgrade.” This allows use of up to 5 different filaments, commonly for different colors, but also for different types of filament, dissolvable supports, etc. The MMU was completely re-designed for the MK4. While this version is having great success on upgraded MK3S+ printers, the developers ran into reliability problems using it on the MK4, and so it has been seriously delayed — so much so that Prusa sent a US$50 voucher to everyone with a long-standing order for this upgrade. I used my voucher to by some of their filament, and the MMU3 did eventually ship. Ah, the price you pay for being on the bleeding edge.

Some 3D printers are “enclosed”, that it, the print mechanism is walled off from the room it’s in. For many others, including the Original Prusa MK3/MK4 line, an enclosure is an extra-cost option. Enclosing a 3D printer provides these benefits:

• It helps maintain a constant temperature for more reliable prints;
• Constant temperature may reduce electrical consumption;
• It keeps noise in;
• It keeps dust out (and may keep prying fingers out of places they ought not to go when the printer’s running or cooling down);
• It allows for dealing with particulate matter and noxious fumes that some filaments give off, either by filtration or by exhausting these to the atmosphere.

Since the MK3/MK4 family has been around for ages, there are quite a few enclosures suitable for it:

• Several do-it-yourself enclosures using Ikea Lack tables;
• Plans to buy for this fancy enclosure, from JK Tech;
• Plans to buy for this other fancy enclosure, on Kickstarter;
• Prusa’s own MK3/MK4 enclosure;
• FYSETC Metal Printer Box Noise Cancelling Enclosure;
• Atmos3d enclosure for MK4;
• PrusaBox by PrinterBox;
• Delack by 3D Sourcerer.

I wound up choosing, and building, the Delack enclosure, and it did in fact make my printing more reliable. I wrote a detailed review of that as well, published on I Tried That. It took a while to print all the parts for the Delack. But it saves money compared to some of the other options, it has many options for the enclosure, lets you see you print from any direction, and it looks great! I recommend this enclosure for MK3/MK4 users, Original Prusa Mini users, and anyone with a similar-sized printer.

Conclusion

The Original Prusa MK4 is a great printer! This printer is far more usable and predictable and consistent than some other printers I’ve tried. It’s made in Europe, not in China, so it costs more, but in my opinion it’s well worth it. Time will tell whether the incoming competition from the Chinese makers will keep up, fall behind, or move ahead.

A Tiny Request, and Full disclosure

If you’ve read this far, please clap for this article below (as many times as you like), and please follow my profile and/or the I Tried That e-zine — thanks!

I paid retail for this printer direct from Prusa, and did not initially advise that I would be reviewing it. I did break cover and ask if they could move me up the queue a bit since I planned to write this full and detailed write-up, but they declined. So I did not receive any special handling, and hence this review came late to the party. I’m not one of those annoying “paid influencers” who disguise their ads as reviews, though, so this is what’s expected.

Affiliate Notice: If you want to buy this printer direct from the factory after reading my review, please use this affiliate link, so both you & I will receive Prusa credits (“prusameters”) toward a free roll of Prusa filament or other potential Prusa purchase. This helps fund my writing on I Tried That. Thanks!