Prusa Research has delayed the release of the MK4 variant of its latest multi-material unit, the MMU3, to an undetermined date.
The MK3S+ version of the MMU3 was released in July, and “is receiving excellent feedback”, according to a recent Prusa blog post – enabling users to achieve multi-material prints from Prusa’s single-nozzle 3D printers.
When it comes to the MK4’s MMU3, however, Prusa says it’s facing challenges in achieving a level of performance that lives up to the MK3S+ version. This became most noticeable during the summer, when ambient temperatures rose at its test farms, and issues were caused by “thin strings of filament that started to accumulate near the drive gears”, the company says.
These strings were noticeable on the MK3S+’s MMU3, but Prusa says the printer’s open design and straight filament path mitigated any issues. The MK4 is a different story, with the filament stringing appearing more frequently and resulting in “a lot of issues with repeat loads and unloads.”
The problem sent Prusa back to the drawing board for the MK4’s MMU3 to create a new filament change strategy, which Prusa says eliminates filament stringing by performing an action similar to a cold pull. However, the fix affected other parts of the MMU3 system – sending Prusa on an ongoing fine-tuning mission that predominantly focuses on issues related to filament sensing and filament “not going smoothly through the extruder”.
Prusa expressed hesitancy to provide a new timeframe to ship the MK4’s MMU3, saying it simply isn’t sure if it’s just around the corner or further away.
“It’s quite possible our testers will confirm that the latest changes solved the listed issues – and we will be ready to start shipping within a couple of weeks,” Prusa says, “But there is also the possibility that the solution won’t be sufficient and we will need even more time to get everything right.”
By way of apology, all users who have ordered an MMU3 for the MK4 will receive a $50 voucher for future orders via email later this week. Those who ordered the MMU2S to MMU3 upgrade for the MK4 will receive a $15 voucher. Both customer groups are also free to cancel their existing orders.
Delays are not altogether uncommon for Prusa, with the Prusa XL being a recent example. Just last week, the company posted about its successful navigation of supply chain difficulties and committed to shipping all preorders made in 2021 by the end of this year.
For more on Prusa’s MMU3 filament change strategy – as well as the current challenges it faces in getting the MK4’s MMU3 up to its standards – read Prusa’s MMU3 update blog post.
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