Upgrading My Prusa Farm: MMU3, Spool Holders, and a Jessie Spool Extender
Not sure if you’ve guessed it yet, but I’m a pretty big Prusa fan. My small, but mighty printer farm consists of:
2 MK4S printers
1 MK4 printer (currently awaiting its upgrade)
1 MK3S+ printer (upgrade to MK4S just arrived!)
With all my printers now standardizing on MK4S models housed in Prusa-branded enclosures, I started thinking: What can I do to up my game?
While I eagerly await the arrival of the Prusa Core One, I decided to take the plunge into multi-material printing with the MMU3 (Multi Material Upgrade version 3). But I had one key requirement:
The Challenge: Keeping It All Inside the Enclosure
Why is this so important to me?
Dust Control: While my print farm area doesn’t get dusty, the potential is always there due to the woodworking side of my shop. Despite all my efforts with air filtration and dust collection, I want to ensure my printers stay protected. The enclosures provide that added layer of security.
Temperature Stability: In the winter, this area of my shop can drop into the lower 60s. The enclosures help maintain a stable print environment for the best chance of success.
So, the search began for a solution that could house the MMU3 inside the enclosure while maintaining functionality. After some deep dives into forums and ideas, a random search on Prusa’s Printables site delivered the perfect answer.
The Perfect Solution: MMU3-Compatible Spool Holders
I discovered a model on Printables called Filaments and Prusa Buffer MMU3 in Prusa Enclosure with MK4. This design immediately stood out because:
It’s compatible with the new fan upgrade that comes with the MK4S.
It had fantastic reviews.
It builds upon another excellent design, the COBRA System for Original Prusa Enclosure.
By combining the two systems, I found what I believe to be the perfect solution to the MMU3-in-enclosure challenge.
Why These Spool Holders Are a Game-Changer
The spool holders aren’t just great for the MMU3—they’ve revolutionized how I organize my entire Prusa farm. I’m using them across all three enclosures, not just for feeding filament but also for storing open rolls I jump between.
Even better, the MK4S spool holder variant fixes the stock issue of rolls running into the new fan. In my opinion, these spool holders are a must-have upgrade for anyone with an MK4S in an enclosure.
The Jessie Spool Extender: Solving a Unique Problem
While these upgrades have been fantastic, I encountered one small issue specific to Jessie PETG spools. If you’ve used these, you might know that one side of the spool has a slight indent. This causes the spool to shift left on the right side of the enclosure, coming uncomfortably close to the extruder as it rises on the Z-axis.
To solve this, I designed a Jessie Spool Extender, which keeps the spool securely aligned and prevents drift. It’s easy to print and works seamlessly with the upgraded spool holders. You can grab the design on Printables here: Jessie Filament Spool Extender.
Looking Ahead
While I patiently await the arrival of my MMU3, I’m already reaping the benefits of these upgrades. My print farm is now more organized, efficient, and ready to handle multi-material printing—all while keeping my spools safe, clean, and easily accessible.
If you’re working with Jessie filament or have an MK4/MK4S in an enclosure, I highly recommend checking out these solutions. They’ve been game-changers for me, and I’m excited to see how they inspire even better results in the future.