What I Build

Little Cube - My Lockdown CoreXY Build

Five months of lockdown. One compact CoreXY printer. The story of building Little Cube - a 100mm³ fixed-bed printer designed for portability and built for fun.

mr.d

04 Oct 2025 — 3 min read

I was looking at my two CoreXY printers one day and something clicked.

The 300x300mm HEVO I'd built from a "Good Luck" kit. A larger custom build made from leftover parts. Both solid machines. Both worked well.

But 90% of what I was printing fit in a 100x100x100mm cube.

Large beds take 5 minutes to heat up. The printers are heavy - hard to move around when I need to repair or upgrade parts. They need dedicated space - you can't just find a spot for them. And I couldn't travel with them. When I wanted to demo something at the office? Not happening.

Then lockdown happened. Time opened up. And I had an idea.

Large custom CoreXY 3D printer occupying significant workshop space — My larger custom build - capable machine, but heavy and takes up serious space

The Third Build

This was my third printer. I love building printers - there's something about designing and assembling your own machine that just works for me.

The HEVO taught me CoreXY motion and connected me to RepRap - that incredible open-source community where everyone shares designs and helps each other build. I started contributing too: parts on Thingiverse, troubleshooting help, pull requests to Marlin.

The larger build taught me to work with whatever I had and think big.

Now I wanted to go small. Intentionally small.

What I Wanted

Space optimization. Footprint just slightly larger than a filament spool. No more massive printers eating up workspace.

Less tuning hassle. Fixed bed that stays put. Smaller print surface meant less leveling drama.

Portable. Something I could carry to the office for demos and bring back home without help.

Belt-driven Z. I wanted to try a belt system instead of lead screws - figuring out the right ratio would be part of the challenge.

Compact hotend. Just 30mm wide - in a 100mm printer, every millimeter counts.

100x100x100mm volume. Perfect for 90% of my prints.

And honestly? I wanted it to be fun. Over-engineered in a good way.

SketchUp 3D model showing the Little Cube printer design with visible frame and components — Early SketchUp design - figuring out how to cram CoreXY motion into a cube barely bigger than a spool

Five Months

January 18th, 2020 to June 15th, 2020.

Designed in SketchUp. Printed parts on my existing printers - about 1kg of PLA+ for all the structural pieces. 2020 extrusions for the frame. MGN12 rails for smooth motion. CoreXY belts I'd learned to trust.

The Z-axis was the interesting bit - belt-driven with a pulley arrangement giving 1:10 mechanical advantage. Smooth. Precise. Different from anything I'd built before.

Close-up of Little Cube belt-driven Z-axis showing pulleys and belt routing for 1:10 ratio — The block-and-tackle Z-axis - one stepper, multiple pulleys, 10:1 mechanical advantage

Not A Kit

When I say "over-engineered," I mean it takes commitment.

You need tools. Allen keys, files, crimper, soldering station. You need to source cables, terminals, hardware, belts, extrusions cut to length. I had all of this already stocked - one of the reasons I could build during lockdown when everything was shut down.

And you need another printer to print the parts for this one.

There's a GitHub repo. A jig.stl file. No step-by-step instructions.

It's a project, not a kit.