Prusa i3 MK3S 3D Printer Review

An incredible desktop 3D printer for a great price
John John (304)
Our rating: 4.75/5

The Prusa i3 is an open-source, self-replicating printer. There are many great 3D printers on the market that are based on Prusa's designs. Yet, I keep hearing that the original Prusa printers are the holy-grail of desktop 3D printing, so I decided to take the plunge and buy a MK3S.

The MK3S is sold as a kit or fully assembled. Currently, the kit is around $750, and the fully assembled printer is $999. In both cases you'll have to pay for shipping, and there is a lead time of about two weeks due to the high demand. I ordered and will be reviewing the fully assembled model. The important distinction is that I will not be able to give much feedback on the assembly of the kit, but I will provide a few details for those interested.

MK3S Kit Assembly

First, Prusa's site claims it should take 6-10 hours to assemble the printer (this is why I chose the assembled version). If you've never built a 3D printer like this, you might want to take the time to assemble it. Fortunately, the printer comes with a selftest to ensure there were no assembly problems. So the selftest plus the calibration wizard (discussed later) should give you some confidence in doing the assembly yourself.

With that said, let's dive in!

Prusa i3 MK3SPrusa i3 MK3S ×1

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MK3S first impression - Haribo gummy bears

Let's start from the beginning. Ordering the printer online was painless, but there was a two week lead time plus shipping from the Czech Republic took about five days. Having been trained by Amazon to expect near immediate delivery, I was especially anxious waiting a few weeks to receive my MK3S.

But after a bit of a wait, I finally got notice from DHL that my package would arrive that day. The box arrived in perfect condition, which was a bit of a relief. The first thing I noticed after opening the box is that everything was carefully designed, even the packaging was high quality and everything was neatly packed.

I pulled everything out of the box, starting with the Haribo gummy bears. I was pleased to see silver Prusament PLA in one box and various tools and materials in another. The MK3S ships with everything you'd need to get started printing.

Overall, my first impression is that Prusa pays extreme attention to detail. This was true of the packaging, the additional tools and materials, and the printer itself, which you will soon see.

Attribute Value
Build volume 21 x 21 x 25cm
Build surface Removable magnetic spring steel sheet with PEI surface
Print materials PLA, ABS, PET, HIPS, Flex PP, Ninjaflex, Laywood, Laybrick, Nylon, Bamboofill, Bronzefill, ASA, T-Glase, Carbon-fibers enhanced filaments, Polycarbonates, and more
Filament diameter 1.75mm
Nozzle diameter 0.4mm
Extruder type Bondtech
Heated bed Yes
Maximum travel speed 200mm/s
Layer height 0.05mm
Dimensions 40 x 50 x 55cm

This will probably be the shortest and most uninteresting section of this review. As mentioned previously, I ordered the fully assembled printer so there was nothing to assemble. I removed a bit of foam protecting the nozzle, and I had to clip off some zip ties that secured the build plate, and after plugging in the printer, physical setup was complete.

Prusa i3 MK3S calibration wizard

There are a few features of this printer that really standout, and the calibration wizard is one of them. One of the major challenges with desktop 3D printers is getting a proper first layer. The first layer is the most important part of the print, and many things can go wrong. Some of the reasons for a crummy first layer are as follows:

  • Crappy build surface (uneven or not prepared properly)
  • Bed not level
  • Wrong bed temperature
  • Bad z-height

The z-height is the distance between the nozzle and the build surface. The z-height must be just right in order to get a good first layer. If the nozzle is either too high or too low, there will likely be problems with the print.

The calibration wizard ensures that a) the bed is perfectly level, b) the x, y, and z axes are properly calibrated, and c) that the z-height is properly adjusted. Most of the calibration process is automated, but during the z-height calibration, the printer will print a first layer and give you the chance to adjust the z-height to perfection. The manual provides a clear diagram of what the first layer should look like, and by turning the knob on the controller, you can adjust the z-height to one-hundredth of a millimeter precision.

The full name of the removable sheet is "Double-sided textured PEI powder-coated spring steel sheet". There's a lot of buzzwords in there, so let's unpack this.

Spring Steel Sheet

Basically, this is a flexible, metal sheet.


You guess it. The sides are buy one get one free. Jokes aside, some print surfaces are uni-directional ("this side up"), but you can use either side of this build surface for printing. So if you ruin one side of the sheet, for whatever reason, you've got another side to print on.


The heatbed includes embedded magnets that firmly hold the steel sheet in place. When the print is finished, you can easily remove the sheet. If the print is stuck to the surface, you can bend the sheet and remove the print.

PEI Powder-Coating

PEI (Polyetherimide) is a thermoplastic used on build surfaces because of its chemical stability and adhesive properties. The nice thing about a PEI sheet is that it requires no surface prep, meaning you won't need to use glue, hairspray, tape, or anything else. Some people use solid PEI sheets, but this is a metal sheet coated with PEI powder.


If you've printed on a smooth surface, you've probably noticed that the bottom of the print is always super smooth and shiny, unlike the rest of the print. This textured build surface makes the first layer a little more consistent with the rest of the print. When ordering the MK3S you can choose either a textured or smooth sheet.

Prusa i3 MK3S mesh bed leveling

Once you experience automatic bed leveling, you can't go back. Bed leveling is extremely important, and leveling manually is a huge pain. The MK3S uses a "mesh" bed leveling system, which means before each print, the nozzle visits nine locations across the bed and uses a laser to find the proper distance from the nozzle to the bed. It then stores the corresponding z-height at each location, and automatically adjusts the print to ensure that each layer is perfectly parallel to the bed, with the perfect z-height.

This saves time and greatly reduces human error. I can say with certainty that many failed prints I experienced in the past were due to improper bed leveling. Either the bed was out of level or the z-height was off. With the MK3S properly calibrated, I have yet to experience a failed print.

Prusa i3 MK3S extruder and hotend

Direct drive extruder

The MK3S uses a Bondtech direct drive extruder. "Direct drive" simply means the extruder is connected directly to the hotend (and moves with the hotend along the x-axis). This is contrasted with a Bowden extruder where the extruder is typically mounted on the top or side of the printer then fed through a long tube to the hotend. There are pros and cons to both designs, but the direct drive design typically leads to more reliable prints, especially for flexible materials.

Filament sensor

The extruder comes with an IR filament sensor. So if you run out of filament in the middle of a print, it will stop the print automatically!

Autoloading and unloading filament

The firmware also comes with an autoload and unload feature. The autoload feature lets you choose your material (PLA, PETG, etc), then it heads up the nozzle to the appropriate temperature and then prompts you to insert the filament. The sensor detects when the filament has been inserted, then continues to load it automatically.

Similarly, when you're finished with your print, the nozzle has typically cooled down. You can use the auto unload feature, which also heats up the nozzle and automatically unloads the filament when ready.

Prusa i3 MK3S first print - benchy.

I had never had a better print than my first print with the MK3S.

Well, to be perfectly honest, my very first attempt with this machine led to a spaghetti mess because the print came loose after a few layers. I tried a few times to no avail. But I did recall Prusa suggesting to frequently clean the sheet with isopropyl alcohol, and it worked like a charm.

After properly preparing the PEI sheet, the first print was fantastic. I chose to print "benchy," which was already loaded on the SD card that shipped with the printer.

This might be an odd thing to include in a product review, but I think it's an important thing to consider. I've messed with a few printers that either had no instructions, or the instructions were in very broken English. This is especially a pain when the printer requires a lot of assembly.

Fortunately, this is another area where Prusa shines. The printer ships with a very high quality manual that includes pertinent information about the printer, but also serves as a general guide to 3D printing.

And besides the manual, there is a wealth of information online to help you succeed with this printer. Some of the most valuable resources I've used so far are the MK3S new user's guide video and the Prusa materials guide, but there's a lot more to explore.

Prusa Slicer screenshot

One thing I found helpful is that Prusa has developed its own slicer. Previously, I used Cura, and while it was easy to use, I always questioned whether the profiles I set up were truly optimal for my printer. With my Ender 3 I experimented a lot with various profiles, and I was never fully confident in my settings.

I decided to use PrusaSlicer with my new printer, and I definitely felt good knowing that the slicer was designed with my printer in mind. I believe this contributed to a smooth first experience with the printer.

Users with more advanced needs may prefer other slicers, but I need something that just works and doesn't get in the way. So the PrusaSlicer is exactly what I need for now.

Baby Yoda printed on a Prusa i3 MK3S

To be completely honest, I rarely print large or complex things. I generally like to design and print small parts that take less than four or five hours to complete. This is partially because I learned to print on budget printers, and I've seen too many failed prints hours in.

But for the sake of testing this printer more thoroughly, I decided to print something that takes a little longer (close to ten hours) and is a little more complex. I printed a Baby Yoda model I found on Thingiverse, and to make things interesting I printed with full supports.

Overall, the supports were overkill. There are four support settings:

  • None
  • Support on build plate only
  • For support enforcers only
  • Everywhere

I chose everywhere, which was likely not necessary for this print. But I did want to see how well it handled the supports and how easy they were to remove.

In the end, I think the print turned out great, although I did break off a finger trying to remove supports underneath his hand.

If you've gotten this far in the review, you can probably predict that I'm going to recommend this printer. The only question is price. If you're prepared to spend $1000 on a 3D printer, this is probably the best you can get. If you don't have the budget, and want a good printer with similar specs, I recommend the Creality Ender 3.

I've been using this printer for over a month now, and I'm still extremely pleased with my experience. Soon I will work on adding OctoPrint and a nice LED light across the top.

The best of the budget 3D printers.
Michael Michael (175)

Budget doesn't have to mean bad when it comes to 3D printers. You can find a great 3D printer for under $300.