Over the past week, a lot of progress happened on the CORE One Mini. While it may not look like a giant leap forward at first glance, this phase involved countless hours of preparation work, experimentation and more than a few unexpected "surprises." And yes: you've read the title correctly, there are files for you to download and try out on Printables right now.
One of the goals from the beginning was to make the CORE One Mini feel like it could have come straight out of the Prusa factory. That also meant getting the color right - which turned out to be a budget topic all on its own.
The original Prusa CORE One uses a very distinctive "Prusa Orange" alongside a black glittery powder coating similar to Galaxy Black. Finding a close match turned out to be more complicated than expected. Rather than settling for "close enough," I decided to run a series of paint experiments.
Over multiple test panels, different paint mixtures, finishes and application methods were compared. In the photos, you can see experiments #1 through #9, which I already posted on Reddit last week and let you all guess. For reference, the original CORE One color sample is #2.
After a few failed experiments and several "close enough" attempts using various paints I had lying around, custom color mix #5 emerged as the clear winner. It captures the appearance of the original color remarkably well while remaining compatible with a practical paint system for this project. This was only possible thanks to your donations to the GoFundMe campaign, which made it possible to have a custom paint mixture developed specifically for the CORE One Mini.
A huge thank you goes to Charly Vieselthaler, who runs a local paint dealership here in the region. His ability to create custom paint mixes is nothing short of wizardry and without his expertise I would probably still be staring at paint samples wondering which direction to take.
The paint ultimately selected is a Mipa 2K-PU-Industry-Prefilled-Spray, a 2-compontent polyurethane topcoat with a custom color mix and metallic pigments. The exact color recipe is not publicly available - if you are from the Region, Charlie is your best shot - otherwise i'll recommend an autobody shop that can creat custom paints from a sample.
Before any paint could be applied, every metal part needed proper surface preparation. Since the printer will be an indoor product, I decided to take the "easy" route and use a monocoat paint system - no primer, no clear coat, just multiple layers of paint.
This meant the "only" preparation required was sandblasting every single component that would later receive paint. While it is one of those jobs that rarely gets much attention in project updates - and is honestly incredibly boring - it is absolutely essential if you want a durable and professional finish.
After an evening spent in a cloud of blasting media, the entire collection of sheet metal parts was finally ready for paint. And yes, for planar parts, sanding with P120 grit would also be an option. It is crucial to work quickly when doing it this way. Bare sandblasted steel is prone to rusting. A drop of rain, a fingerprint, or even excessive humidity can ruin the work and cause corrosion to start beneath the paint months later on.
The key is to blow off all loose blasting media and then clean and paint the parts within a few hours. By cleaning, I mean using a proper degreaser. Depending on the blasting media used, IPA can work, but silicone remover is generally the better choice. Spray-can degreaser works particularly well for smaller parts like this - but if you want to gor larger, for example paint car parts, you probably won't be able to afford this method.
Just after I had painted the first few parts, disaster struck: One of the spray cans had a faulty valve. Instead of producing a normal spray pattern, it suddenly turned into something that looked more like a fountain. Imagine dropping Mentos into a bottle of cola: except the cola is metallic black paint and it's pointed directly at your freshly prepared parts.
Luckily, I reacted quickly and only a handful of parts ended up with paint splatters. The situation was more frustrating than catastrophic, but several parts were nevertheless ruined and had to be stripped again.
The result? Back into the blasting cabinet they went.
Thankfully, the 2K PU paint fully cures within 24 hours, so reworking the damaged parts was relatively straightforward. Once everything had been cleaned up and prepared again, the painting process continued as originally planned.
This second attempt went exactly as expected. Every visible metal component received its final finish - even surfaces that will never be seen once the printer is assembled. For the first time, the project started looking less like a collection of DIY parts and more like a professionally manufactured product straight from the factory.
Seeing all painted components laid out together was one of those milestone moments that makes all the effort worthwhile.
With the paint work completed, assembly could finally begin: the base assembly is now put together, and many of the previously separate components have found their permanent place "within" the machine. While there is still a significant amount of work ahead, the project has now reached the stage where individual parts are turning into a recognizable printer.
This is also an important milestone because it allows me to verify fitment once again in the proper assembly order.
Since many assemblies have already been tested multiple times during development, putting everything together should now go considerably smoother and faster. That said, I'm still taking my time to verify that every component is present and that I haven't accidentally missed anything along the way. At this stage, I'll also be going through the BOM and part list one more time.
Since the base assembly is now complete and the design has matured sufficiently, I have also started uploading files to the regular Printables model page, that i've create a few weeks ago as a placeholder: Prusa CORE One Mini (Community Edition)
At this point, both the printed and metal parts represent the final versions that were physically assembled. While I can never completely rule out small adjustments during final testing, I currently do not expect any breaking redesigns of the parts involved.
That said, if you're planning to build your own CORE One Mini, I would still recommend waiting a little longer before committing to a full build. There is still some work left to do and I don't want anyone diving into the project before seeing its full scope - there are a lot of custom parts to modify and make.
The focus now shifts away from paint and surface preparation toward final assembly.
Sharp-eyed readers may have noticed that the side panels are still missing. I've already made them, but the bend radii turned out wrong due to the unusual geometry and aswell as distorted holes, since they are too close to the bends. As a result, I'll need to remake those parts using a different bending strategy with relieve cuts.
Over the next few weeks, the CORE One Mini should finally start looking like a complete printer that stays assembled.
From this point forward, my job shifts to mechanical validation, followed by the first power-on test after I've assembled the machine. At that stage I probably won't be touching calibration, homing, or first-time setup yet - I simply want to verify that every subsystem works as expected: steppers stepping, the extruder extruding, heaters heating ... you know the drill.
And then, next stop: Firmware.
Thank you to everyone who has been following the CORE One Mini project and contributing feedback along the way. The comments, ideas, and suggestions play a meaningful role in shaping the direction of the build. Many refinements - both small details and larger design choices - are directly influenced by your input.
Beyond the technical impact, the ongoing support also helps maintain momentum through longer development phases. Having people engaged with the process adds motivation and perspective throughout the project.
I really appreciate everyone being part of this journey and helping shape CORE One Mini into what it is becoming.
If you want to learn more about the project, make sure to checkout the main post "CORE One Mini - The Rocky Road to a Prototype." for the complete background and FAQ.
If you intend to buy a Prusa machine, you can use the referral code "@suit" at checkout in the Prusa online shop. This will give you some Prusameter points and 1 kg of free filament and i'll get some points aswell (which I can use for some free filament). Or you can just download, like and make some of my models here on Printables and even consider to become a member in my Printables club.
I've also set up a GoFundMe campaign to tackle the costs. Thanks to everybody who has donated a few euros already - that means a lot and helps me cover the expenses.
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