The new hotness in 3D printers is – and has been for a while – dual extrusion. With two extruders and the requisite filament supply, it’s possible to print objects in two colors or two different materials. There’s a problem with this setup, though: each extruder requires a separate motor, greatly reducing the print area should you want to print in two or more colors. [Carl] and [Brian] think they have the solution to this with their dual extruder that is powered by one stepper motor.As you can see from the pic above, the idea is relatively simple. Two strands of filament are fed past one gear attached to a stepper motor. Each strand is moved into the hot end through two idler gears and side of the extruder feeds into the hot end is determined by the rotation of the motor. It’s really one of those, “why didn’t I think of that” ideas.[Carl] and [Brian] are also offering a quad extruder, a dual-sized extruder able to pump four different filaments onto a printer bed. With this, we expect some people to experiment with CMYK (or CMYW) prints, truly turning any 3D printer into a machine that prints full color parts.