For some would-be 3D printing customers, the barrier was watching half the filament go into the trash. I’ve been coveting a multi-material 3D printer for a while. Then I watched videos of those machines producing piles of purge waste every time they changed colours or materials. Printer poop. Bins of it. That was enough to spook me off. The problem is inherent to single-nozzle multicolour systems. Whenever the printer switches filament, it has to push all the old material out, ’til the new...