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Prusa i3 MK3

By Matt Stultz / Sep 23, 2017

Prusa i3 MK3

The first night of our testing was drawing to an end and everyone on the team was anxious. We all knew that a package was arriving soon. This machine wasn’t able to make it on time via standard shipping options, so it was being flown from Prague to New York and driven in a rental car up to Rhode Island. My phone rang and a few minutes later I was excited to show the team the only two Prusa i3 MK3 prototypes in the world.

The i3 MK2 has garnered quite the reputation over the past year, and winning our top spot during last year’s test didn’t do anything to hurt the situation. Jo Prusa and his team didn’t rest on those laurels though, they had to push it even further. The spec list of the MK3 makes it clear that Jo and his team are not just making these machines for their customers, they want a great machine for themselves as well.

Lots to Love

The MK3 has a lot of changes to be excited about, so let’s point out some highlights. One criticism that has plagued Prusa’s printers since the Simplified Mendel is the usage of threaded rod as a construction material. The MK3 finally does away with it in favor of the popular 20mm aluminum extrusion for its base. This will make it easier for builders to ensure a square frame, and really makes the new machine look a lot more polished. Cable mounts have also been strengthened to help prevent wear and tear caused by constant motion.

The MK3 has a new controller called the RAMBo Einsy, which sports the biggest update to the machine and enables new stepper drivers: the Trinamic TMC2130. With these new drivers, the MK3 is able to detect when the motor has stalled or is missing steps. This eliminates the need for endstops; the MK3 just moves each axis to its end and detects the change in the EMF in the motor coils when the carriage comes in contact with the part at the end. This has also been implemented to detect problems during printing. If your part begins to lift up and your extruder runs into it, the MK3 will pause and alert you rather than continue printing a bad part. The Trinamic drivers are also configured to ensure the machine runs quietly. While we didn’t measure how loud the machines were this year, we were all blown away by how quiet the MK3 was during our testing.

The MK3 doesn’t stop sensing with collisions, it’s also monitoring your extruder. Extrusion issues are some of the most common problems that plague 3D printing. The MK3 will monitor your extruder, attempting to detect jams or missing filament and pause the print if it thinks things are not correct, potentially saving your print.

One of the things everyone loved about the MK2 family was the PEI coated beds with separate heat zones, and the magnets for use in calibrating the machine. Now the bed is even better, featuring a magnetically attached spring steel sheet that has been bonded with PEI. When a print finishes, you can quickly pull off the current bed, stick on another, and start printing while you wait for your part to cool enough to remove from the bed. The removal process is now painless as you simply flex the bed once it has cooled and the part pops right off. We have seen this in other implementations, but when it is combined with the PEI, it is really something special.

Pursuing Excellence

Our test prints came out incredible. We initially thought that they would beat this year’s MK2S print. However, after the judging was complete, the MK3 fell behind its sibling by a couple points in our scoring. Although, we have to remember that these were the only two prototypes the Prusa team had. They had not yet had time to fully tune these machines before rushing them to us. It is very likely that, by the time you are reading this, the final version will be ready to go and our future testing will see the points add back on.

This machine really excited the team with how incredible it was. When Jo and his team begin shipping the Prusa i3 MK3 in the fall, I think you will be excited for it too, and Jo will have another hit on his hands.

Specs
Prusa i3 MK3 Prusa Research
Manufacturer:Prusa Research
Price as Tested:$999
Build Volume:250x210x200mm
Bed Style:Heated, Removable, PEI Coating
Filament Size:1.75mm
Open Filament:Yes
Temp Control:Yes, extruder (300ºC max); bed (120ºC max)
Print Untethered:Yes (SD card support and Wi-Fi via custom integrated octoprint)
Onboard Controls:Yes (clickable scroll wheel with LCD)
Host/Slicer Software:Prusa Control and custom Prusa Slic3r
OS:Mac, Windos, Linux
Firmware:Marlin
Open Software:Yes (GNU GPLv3)
Open Hardware:Yes (GNU GPLv3)

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Why To Buy

The new MK3’s spec list shows they are not just trying to please their customers, they want a great machine for themselves as well — and will continue to make it better.

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Pro Tips

When a print finishes, swap in a new bed and start printing while you wait for your part to cool.

If your extruder runs into a print, the MK3 will pause and alert you rather than continue printing a bad part.

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