We were changing nozzles, print and ambient temperatures, and speeds. Troubleshooting the cause of these thin strings of filament led us down a rabbit hole of investigating what changed and researching ways to make the tips perfect again. On the MK4, however, these wisps of filament appeared much more frequently and caused a lot of issues with repeat loads and unloads.Īn extreme case of the filament string forming on the tip Plus, the extruder on the MK3S+ has a fairly open design and the filament path is completely straight, so we did not see any problems with them in our testing. On the MK3S+, these strings would also appear, but to a much lesser degree. This was caused primarily by thin strings of filament that started to accumulate near the drive gears. However, as soon as summer came and the ambient temperatures in all our test farms increased by 6 to 10 degrees Celsius, we started encountering a drop in reliability of the MMU3 on the MK4 (but not on the MK3S+). The only problem at the time was our manufacturing capacity. We were putting together units for external beta testers and we expected the production units to start shipping in late June. When we first announced the MMU3 in March 2023, we had everything ready and working reliably with both the MK3S+ and the MK4. They are also based on a different motherboard and firmware architecture of the printer itself. Each printer uses an entirely different extrusion and hotend system. So one has to wonder, if the MMU3 works fine on the MK3S+, why is it not working just as well on the MK4? The differences between them are in the print heads. Why? Understanding MMU3’s reliability drop on the MK4īoth MK3 and MK4 use the identical MMU3 unit – there’s no difference between them. However, we’re having a hard time matching the MK3S+ performance.

Naturally, we want the MMU3 for the MK4 to be just as reliable and efficient, if not even more. Achieving huge 70+ hour 5 color prints with zero interventions is exactly what we were aiming for. We’ve been shipping the MMU3 upgrade for the MK3S+ for over three months now (since July) and we’re thrilled to see that the reliability observed in both our internal and external beta testing is also manifesting in customer experiences. The primary reason for creating a successor to our MMU2S was to enhance its reliability and ease of use without the need for lengthy fine-tuning and calibrations. In this development diary, we’d like to talk about the technical problems we’ve encountered, how we’ve solved them, and what’s left to figure out before we can start shipping the production units. While the MMU3 for the MK3S+ has been out for more than three months and is receiving excellent feedback, we keep postponing the MK4 variant further away. The Original Prusa MMU3 is our efficient solution for the MK3S+ and MK4, enabling these single-nozzle 3D printers to print using up to 5 filaments.

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