CORE One Mini - A Status Update and the Rocky Road to a Prototype.

Some folks have already seen some of my announcements, updates and discussions about a Prusa CORE One Mini on various platforms like Reddit. After a few setbacks up until November 2025, the project was put back to the drawing board for the third time by the end of 2025. It is now 2026 and we are calling it a fresh start now. 

That is why I am also moving this to the article feature of Printables (that i never tried before), to hopefully use this as a project diary and give more frequent, smaller updates and also to use the wisdom of the crowd :)

First: Why did I start over two times?

The design goals did not change: they were and still are, to keep the overall aesthetics of the CORE One - just in a smaller form factor and to use the Prusa MINI build plate. But the features and possibilities grew rapidly within a few weeks by the end of 2025. The first proof of concept (a reverse-engineered CAD model of the CORE One scaled down that I did over the course of a few months since summer 2025) showed that everything could fit. But it would not result in a usable machine, since some parts just would not work. For example, there would be no way to plug in a power cord. Those issues were resolved in a somewhat satisfying way in a small-scale rectangular footprint.

But then Formnext happend and the USS Drybox, CORE One+ etc. got announced or released, which resulted in a few observations that did not comply with my perfectionism and "required" a redesign. So I started cobbling together an even more space-efficient version that had the same build volume but a smaller footprint and bigger indents for the side panels to accommodate (hopefully) the USS Drybox and make the side panels look less lopsided with a uniform border width. This second CAD model was looking really nice and promising and I was about to start prototyping outside of CAD.

But shortly after that, the Open Community License with the official CAD models of the CORE One and CORE One L were released. This gave me some insight and allowed me to take a deeper dive into the construction of the machine with exact dimensions and see what was changed by the Prusa Research hardware development team especially in the C1L. Quite frankly, even though the outside of the machines looks quite similar, there was a lot changed on the inside. After all, the machine is larger but has roughly the same mass due to a lighter yet sufficiently rigid construction. And even though the build plate has a different, square aspect ratio, the outer frame is still square.

This really bothered me, because my CORE One Mini draft, with a square build plate, had a rectangular shape on the outside - mostly due to the xBuddy box and PSU taking up space in the back. Both the C1 and C1L are very elegant because they can be manufactured very easily - there are only two lengths of bent sheet metal for the corner pieces - simple and efficient. My CAD models had three different lenghts, with a rectangular footprint.

In the end, my perfectionism kicked in: back to the drawing board for the last time to … square everything up.

So where we are now?

I spent the past few weeks playing a puzzle game where I had to fit the desired build volume into an enclosure with a square footprint that is as small as possible. Long story short: i call this 3rd iteration a success. I managed to combine the design paradigms of the C1 and C1L to merge the best of both worlds and scale it down. The result is now unfortunately a messy and incomplete CAD model that just cobbles together various parts from both printers including custom parts that are essential for the kinematics, as well as the housing parts, including the base plate and overall geometry.

The calculated motion limits of the XY kinematics are 184 x 191 mm - so a 180 x 180 mm build volume with a bit of overtravel left and right, as well as in the front. The extra 11 mm are enough to operate the automatic vent, leave space for the prime line and maybe can be utilized for a compact nozzle cleaning area - we will see.

As for the height, the original goal was roughly 200 mm build height with a motion limit of 205 mm (just like the original C1 with 5 mm overtravel). Due to the hole and cutot positions of the the original C1 profiles, I will need to shift things around a bit so the mounting holes line up properly without needing to drill new ones. If this works out in an ideal world, there should be a printable cutting template to shorten all profiles by 70 mm.

The outer dimensions will be (excluding the display) approximately 344 x 344 x 485 mm (~57.5 liters - for comparison, the C1 has around 95.5 liters and the C1L around 140 liters). 

So the math for XY is done - everything vital fits. Every other component needs to be triple-checked and brought up to a full CAD model again. This will be the un-fun part, for the third time now - but i am very happy with the overall geometry :)

After the XY kinematics, my next concern is the base plate - luckily dimensions are already finalized. Since everything is so squeezed down now, it is shaped in a way so the side panels and the back panel could be sunken in. This will give lots of usable space for spool and tool storage. The cable management in the back panel will be a bit of a squeeze though ;) - since I tried to shave off every bit of material, the back of the base plate is very thin and is not stiff enough anymore. Braces will be needed, as well as some way for cable management, because the cable tie mounting points are gone.

Since I wanted an easy, reproducible process, I opted for 3D-printed braces with square nuts that can be screw mounted. I have already done a few iterations and they are rigid enough for prototyping. In the final design, I will probably have bent sheet metal pieces here aswell.

Road to Victory: What needs to be done before a physical model can be built?

The to-do list is quite long, but the major parts that need to be finalized are:

• Base plate and braces for the base plate (current)
• Alignment of the frame profiles
• Entire heat bed carriage 
• Sheet metal bend pattern for the side panels
• The back Panel with new geometry

 And of course an awful lot of cross-checking measurements  and some “minor” challenges, that i will tackle one by one until they are resolved :)

Stay tuned, I'll post a few of those challenges in the future to source some feedback from you guys.

Frequently Asked Questions

How much will it cost?

My BOM currently does not include a "best-case" calculation yet. It basically covers prototyping with a lot of extra parts, test pieces, etc. The prototype (built upon a regular CORE One kit) will add up to roughly 1,750 euros, excluding shipping and manufacturing costs. There are a lot of leftover spare parts, like an extra heatbed and many integral enclosure and motion assembly parts.

There is currently no public BOM, but I'm keeping track of the parts in a spreadsheet and I am confident I can bring the final cost down to a reasonable level :)

How do you cover the cost?

Thanks to Prusa Research, most of the common parts from the regular CORE One are covered by the sponsored kit I received from them in December 2025. For the rest, quite a bit of money is still needed to cover costs, especially for sheet materials (metal and plexiglass) as well as paint. If you are affiliated with a company that is interested in sponsoring certain parts of the project (especially sheet metal cutting, paint, or powder coating), just drop me a line.

Also, 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 me as well (which I can use for some free filament).Or you can just download, like and make some of my models here on Printables or 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.

How about the firmware?

Yeah, I have thought about that, but this will be a concern once the hardware is done :) If you have experience, just drop me a line - I'll put you on my list and hopefully may contact you at a later stage of the project.

When will it be ready / released?

Since I am a one-man show and work a full-time job, this needs to progress in my free time without neglecting my social life. A rough timeline would be around summer 2026.

Just to make it clear: this is intended to be a DIY project. I will release the CAD data (the custom-made parts) under the OCL on Printables for everybody to enjoy. This is a purely non-commercial product, and you will need to build it yourself and also source or make certain parts. I will not be providing a commercially available kit for the custom parts (unless Prusa Research explicitly allows this).

Where will i find updates & where can i follow the Project?

I'll try to post updates on various channels (like Reddit), but the main source in the future will be my Printables page from now on – so make sure to follow me and spread the word.