qbs: Printable bricks

qbs ("cubes") is an interlocking brick system focused on ease of printing. Incompatible with LEGO.

This model page provides several essential bricks. You can extend the set with plates and tiles.

Background

As a lot of others, I tried to print LEGO compatible bricks before, and I quickly found out it is tricky. The tolerances are not forgiving, and I never got it working properly, calibration bricks or not.

Instead, I decided to give my own design a go. If you look at a LEGO brick properly, you'll realize they are quite thick, which works for the molding process, but is inconvenient for FDM printing – the printer spends a lot of time doing perimeter layers that don't contribute to anything useful.

The brick wall cannot be just one perimeter, it gets really brittle and the slicing process puts holes into the walls. More than two is just increasing the print time.

This is the fifth iteration of my own design, and it has reached a stage where I feel confident publishing it.

Technical information

A 2x4 qbc brick is 15.8x31.8 mm, with 8mm between the peg centers (that 0.1mm on each side of the brick is essential to be able to place them next to each other). qbs brick is (only) 9 mm high, as it saves a bit of time when printing.

So far I have been printing these from PLA of various brands and ages and they generally fit together well. I print everything at layer height 0.2 mm.

Printing tips

Some filaments stick well to the bed, while others tend to break off and cause a mess. If you plan to be around, print only a few bricks, and you have tested your filament spool, you can generally let them print as-is. For longer prints, or for when you are away, I recommend using a brim to print everything as one giant piece, and then use pliers to tear off the brim from the brick itself. It takes a bit of time, but you won't end up with spaghetti.

Building tips

qbs is compatiblem with sites like BrickSet or BrickLink that provide huge databases that list sets and their contents. A lot of sets will contain bricks that do not have qbs equivalent; sometimes you can work around that, sometimes you'll have to do some work and do 3D modelling.