CORE One Mini from CAD to Chaos: Sparks, Metal and High-Power Lasers

A lot has happened in the meantime - this is the point where the CORE One Mini project finally left the comfortable world of CAD and stepped into the slightly more painful reality of sparks, sharp edges and metal shavings. Hours were spent on tasks that an online service could have handled with a single click, but with a limited budget, the only real option was to roll up my sleeves and get my hands dirty.

It's the kind of work that tests patience, attention to detail and endurance - but it's also the moment where the design truly comes alive. So, what milestones did we manage to hit along the way?

Filament Sensor: Trial, Error, Repeat

One of the first things I tackled last week was the long-overdue filament sensor. The original concept technically worked, but it was simply too bulky and positioned in a very awkward spot. Space inside the CORE One Mini is extremely limited and every extra millimeter cascades into other compromises.

This quickly became a proper trial-and-error phase. I started by moving around the original sensors from the CORE One, CORE One+ and CORE One L to see what might fit.

I went through multiple layouts:

• Rotating the sensor orientation
• Rerouting filament paths
• Trying different lever geometries
• Reducing wall thickness wherever possible
• Swapping fastener positions to eliminate dead space

Each iteration looked promising … until it didn't. Either tolerances were too tight, the filament path had sharp bends or the mounting became awkward. After a few evenings of rearranging parts like a mechanical puzzle, I finally landed on a much more compact solution that keeps the filament path clean and serviceable. It still needs some cosmetic cleanup and structural refinement, but the concept works and fits properly now.

Huge shoutout to u/xDerJulien on Reddit for nudging me in the right direction with a simple idea that unlocked the whole layout: using the STEP files from the C1L instead of reverse-engineering the STL of the C1. I was totally blind here - without that hint, I would've burned way more time for the same result.

So how does the solution look? I shaved off everything I could, and it still wasn't enough. The sensor is now sunken through the side panel into the handle - a tight fit, but it works.

Base Plate & Sheet Metal – from Screen to Sparks

On the structural side, I finalized the base plate geometry and the related sheet metal parts. This was mostly about locking down hole patterns, ensuring everything aligned with the profiles, and triple-checking clearances for kinematics, cable routing and panel mounting.

Once I felt confident enough, I moved on to the physical parts. I laser-cut the first prototype components -and yes, whoever said watching 3D printers is mesmerizing clearly hasn't stood in front of a high-power laser cutter. That thing is basically industrial fireworks! It never gets old.

But the romantic part ends quickly - after cutting comes the reality:

Deburring every single edge, cleaning up tabs, breaking sharp corners, sorting parts and checking dimensions. Adjusting bend allowances. And then … repeat :) I ended up cutting and bending about ten brackets before everything fit correctly and every hole had the right diameter.

Getting consistent bends on small parts without distorting them takes patience, especially when tolerances are tight and you really don’t want to scrap a piece you just spent time on. This is a different story in volume production, when you have endstops for your brake - but well, I don’t have such a fancy tool :)

And then … tapping. So much tapping. Again, my tools aren't that fancy, so it was hand tapping all the way. I spent what felt like an entire day tapping M3 threads ;) One hole is fine. Ten holes are fine. 32 holes across multiple brackets in different orientations? That becomes a meditation exercise: back and forth, quarter turn, back it out, clear chips, a drop of oil, repeat. Over and over again.

The highlight was the one M4 thread I cut for the PE/FE Faston connector.

Not glamorous. Very necessary.

The parts are currently raw - not sandblasted, not painted - just functional prototype hardware, we'll figure out the paint at a later stage. But seeing real metal parts instead of shaded CAD geometry or 3d printed haptic prototypes is a huge psychological milestone. It's also proof of concept that shaving everything down to a very narrow strip of steel in the back can still be rigid enough.

Cutting Template for Frame Profiles

Another surprisingly involved task was creating a proper cutting template/marking guide to shorten the frame profiles.

The goal is to avoid drilling new holes and instead reuse the existing hole patterns by shortening everything precisely. That sounds simple - until you realize that:

• Every cut affects hole alignment
• Every tenth of a millimeter matters for panel fitment
• Tolerances stack up quickly in a cuboid-shaped frame

I went through multiple measurement passes, printed test guides, checked alignment against the CAD, re-measured, adjusted offsets and verified that the mounting holes would still line up correctly after shortening. The result is now a jig that creates an exact offset of 70 mm. The idea is that you clamp it down, spray it with some white paint, use it as a guide and then cut off everything that isn't coated black. At least, that's the theory - we'll see if it actually works or if I'll need a different solution.

As with many parts of this project, turning digital designs into physical hardware quickly became a lesson in how much time even small tasks can take. Cutting, deburring, bending and tapping each piece felt endless, but every painstaking step revealed details and refinements that wouldn’t have been obvious in CAD. In the end, the hours spent don't compromise the project - they're the price of making the CORE One Mini real and ready to function - but next time maybe I'll use an online service :D

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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 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 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.