The Original Prusa i3 MK3S+ ($749 in kit form; $999 fully assembled), an incremental upgrade to the Editors’ Choice-award-winning Original Prusa i3 MK3S, is little changed from its predecessor in appearance or performance, but a variety of under-the-hood changes make an already exceptional 3D printer more durable and reliable. Our testing confirmed that the new model consistently produced prints of the same high quality as the MK3S, and it presented no operational problems during our time with it. The MK3S+ takes the baton as our latest Editors’ Choice honoree among mid-priced 3D printers for hobbyists and makers.
A Classic, Now Better Than Ever
The orange-and-black i3 MK3S+ is Prusa Research’s flagship 3D printer, directly descended from the Prusa I2 which the Czech company sold at its 2012 inception. The open-frame i3 MK3S+, a single-extruder model, measures 15 by 19.7 by 22 inches (HWD), excluding the spool and spool holder, which sit atop the printer. (The device comes with two spool-holder rods, so you can feed filament to the extruder with one spool and have an auxiliary spool at the ready.)
The frame consists of a base that supports a square arch to which the vertical and horizontal carriages (along which the extruder moves) are attached. The base also supports the build plate, which can move in and out (toward or away from the front of the printer). In front of the build plate is an orange panel housing a monochrome LCD, with a control knob at the right and an SD card slot on the left side.
The print area for the i3 MK3S+, at 9.8 by 8.3 by 8.3 inches (HWD), is a smidge larger than its predecessor’s 9.8 by 8.3 by 7.9 inches. It’s also slightly larger than that of the Anycubic i3 Mega S (8.1 by 8.3 by 8.3 inches) and considerably bigger than the 7-inches-cubed print volume of the Original Prusa Mini.
You can save $250 by assembling your Original Prusa i3 MK3S+ from a kit or get it ready to go out of the box for $999, as our test unit was. (Note that on purchases of $800 or more, U.S. customers may have to pay an import duty from the Czech Republic on receipt.) As the printer is open-source, part of the venerable RepRap tradition—Prusa Research 3D-prints the plastic parts used in its construction—several companies have created clones of the i3 MK3S+ (most actually of the previous-generation MK3S) that they market for a lower price. However, their build quality is indeterminate, and we suggest that you stick with the real deal, an Original Prusa printer.
Documentation and Software
The i3 MK3S+ includes a user manual, the 3D Printing Handbook. Unlike most 3D printer manuals, which tend to be spartan (and often online-only), the Handbook is a beautiful, professionally printed guide that covers both the preassembled version and the kit. Our printer also came with another signature Prusa accessory, a package of Haribo Goldbären, a.k.a. Gummi Bears. With Prusa’s kits, you eat the bears as a reward for completing certain steps specified in the assembly guide, but no such restrictions apply to the preassembled version.
For software, the i3 MK3S+ uses the company’s own PrusaSlicer suite, which we have seen in both the Prusa Mini and the i3 MK3S. The software, which resembles the popular Cura program, is easy to master, leading you through the process from loading a 3D file, modifying it, “slicing” it to printable form, and saving it. PrusaSlicer has three interfaces or user levels; Simple offers a basic range of settings and is designed to get you up and printing quickly, while the Advanced and Expert modes offer a wider range of tweaks.
Filament Support and Setup
As a filament-based (FFF, for fused filament fabrication) 3D printer, the Original Prusa i3 MK3S+ supports a wide variety of filament types, including but not limited to PLA (polylactic acid), PETG (polyethylene terephthalate enhanced with glycol), ABS (acrylonitrile butadiene styrene), ASA (acrylonitrile-styrene-acrylate, an alternative to ABS), Flex, nylon, carbon-filled, and Woodfill. The printer comes with a 1-kilo spool of silver PLA filament, which is what I used in our testing.
The preassembled i3 MK3S+ required very little work to get up and running. It arrives with a test print (the Prusa name plaque seen above) already printed out and adhered to the build plate. You gently pry it off, assemble the spool holder—which snaps into place on the metal bar atop the printer—then turn the printer on.
You then use the LCD’s control knob to extract the remaining filament from the extruder, twist the knob to Filament In, put a spool of filament on the holder, and feed it into the extruder. Filament should soon start extruding from the nozzle; pressing Yes when you’re prompted will stop the flow. You remove the strand of filament hanging from the nozzle, put the supplied SD card in its slot, select a sample file, and press Print.
Test Prints
I printed eight objects on the i3 MK3S+ at the default 150-micron “Quality” resolution setting, most of which I had previously printed on the i3 MK3S.
Print quality was very similar to the previous model’s: uniformly above average, with only minor blemishes, most commonly an occasional and easily removed tail of loose filament. The MK3S+ did well with fine detail and in handling overhangs.
The Prusa i3 MK3S+ Vs. the i3 MK3S
Prusa has characterized the changes between the i3 MK3S and its successor as minor, offering improved durability but with little change in performance. The MK3S+ has a different mesh bed leveling probe called SuperPINDA, which is temperature-independent. However, Prusa says the previous probe was already highly precise, and the change was merely to compensate for temperature drift. MK3S users may see only a small improvement in first-layer accuracy. This change is more significant for the Original Prusa Mini+, which replaces the Original Prusa Mini. (Prusa has unified the mesh bed leveling probe across all its machines.) Although we didn’t notice any qualitative difference in the prints, I did notice that the bed leveling, in which the probe touches 16 points on the print bed’s surface while automatically leveling the bed, was swift and smooth.
Among the other hardware improvements that Prusa has made for the i3 MK3S+, the Y-axis bearings are held by metal clips instead of the old U-bolts, and some new plastic parts have replaced zip ties in holding the carriage’s smooth rods. The X-axis belt-tensioning system has been modified. The extruder’s plastic parts are also slightly different to improve the cooling airflow.
As these changes are incremental, if you already have an Original Prusa i3 MK3S, there’s no compelling reason to replace it with the MK3S+. Prusa does sell an upgrade kit for $49, but notes that if your MK3S runs without any issues, you won’t see any significant print-quality improvements from upgrading. However, the MK3S+ supports an additional upgrade—Prusa’s $299 Multi Material Upgrade 2S (MMU2S), which enables the 3D printer to print with up to five colors (!) at the same time. You can upgrade the older MK3S with the MMU2S feature, but will need to install both kits, upgrading to the MK3S+ first.
Verdict: A Worthy, if Modest, Upgrade
As an incremental upgrade in Prusa Research’s primary 3D printer line, the Original Prusa i3 MK3S+ offers some modest improvements over the now-discontinued i3 MK3S. Among the changes are an enhanced bed-leveling system, sturdier parts, and improved extruder airflow, all of which serve to make a good printer even better. If you already have the i3 MK3s, you may want to wait until the next generation before replacing it, unless you’re anxious to try the five-color add-on.
If you have never owned a Prusa, be aware that the i3 MK3S+ is the culmination of nearly a decade of refinements to the company’s flagship 3D printer. It’s easy to set up and use, and in our testing consistently produced prints of above-average quality with zero significant problems. The MK3s+ supports printing with a wide variety of filaments, includes the simple yet powerful PrusaSlicer software, and comes with a handsome and helpful user manual and access to Prusa’s extensive help resources and user forums. The MK3S+ is priced at the high end of open-frame printers with similar build volumes; you can find decent budget 3D printers such as the Anycubic Mega S (and others we have yet to review) for a fraction of the cost. But if you don’t mind paying for proven excellence, the Original Prusa i3 MK3S+ easily earns our Editors’ Choice honors and is as good as consumer-grade 3D printing gets.
