If you’ve done any desktop 3D printing and, lets be honest, who hasn’t, right, then you’re aware of the limitation imposed on your creativity by the color of the plastic you’re printing in. Makerbot has sort of addressed the issue with their dual extruder, but it’s really only a tease. Being able to switch from one color of plastic to another only highlights the fact that you can’t print in any of the colors in between.
At first people tried to solve the problem by coloring white ABS filament with markers just before it entered the extruder. This approach worked. For example, the Filament Colorizer by cyclone holds two sharpies and makes your prints new colors. Dry erase markers also work, as demonstrated by scocioba. Also RyGuy. As an alternative, James Corbett has developed an extruder that mechanically mixes different colors of plastic. The idea is that you could have a roll of plastic in basic colors (like CMYK and black) that you just push into the mixing chamber in different proportions to create the full color wheel.
Testing the marker thing was pretty straight forward. People just rubbed a marker on the plastic filament and it did pretty much what you’d expect. Testing the mechanical mixer was an entirely different story. Corbett went through several passive and active designs before he found one that successfully mixed the plastic. Follow the jump to read the conclusion and way ahead from his paper on the subject.