Kurt Hamel is a maker that likes to make cool, fun stuff. He also just found an awesome way to turn paint-by-number kits into 3D printing fun.
To make it work, Hamel prints one color at a time and then switches filaments. The end result is a multi-colored print that is is limited only by the filament colors in your workshop.
Hackaday explains the idea behind it and how it all works:
The idea is simple: You find a paint-by-number layout (apparently, you can find them with a Google search). Use your favorite method to get the outline into a CAD program. [KurtH3] doesn’t really get into the details about this, but some CAD programs will directly import images. Others will require you to trace in Inkscape (or a similar program) and convert to a vector format like DXF that the 3D CAD program can import.
Here’s the trick: instead of extruding the 2D image as one piece, you extrude the numeric regions to slightly different heights. Say you wanted to print a red, white, and blue flag to a thickness of about 5mm and you use 0.2mm layers. You could extrude the white part to 5mm, for example. Then the red parts could be extruded to 5.2mm (one layer higher) and the blue parts to 5.4mm. You could extend the idea to do multiple layers, although that will increase the surface roughness.
Hamel also explains it all in an Instructable page here.
As Hackaday points out, the idea of changing filaments to get different colors is not exactly new (see video above), but it is still a pretty fun re-imagining of a kiddie classic for the 3D printer, which is exactly what Hamel meant it to be.
Photo Credit: Instructable