RepRapPro founder and instigator of the RepRap movement, Adrian Bowyer, with the help of a RepRapPro customer, has come up with a method for multi-material 3D printing with a single extruder.
The idea, originated by Bowyer’s customer Dr Michael Fairhurst, is to treat the filament as a railway train approaching points, and to design the filament path to allow filaments to merge into a single hot end. The RepRap founder implemented Fairhurst’s concept by locking three Bowden tubes into a printed component, specially designed for the purpose, that joins the filament to a single printhead. Then, when it comes to change colours while printing, one line of filament can be retracted while another is fed to the hotend.
Bowyer explains that this method does away with some problems associated with multi-headed machines. For instance, G-codes no longer have to account for more than one Z-axis height, associated with each extruder. Dripping filament from a recently used print head is no longer a problem either. And, in order to shift from one colour to the next, the machine can purge the last colour while printing the interior of an object before going onto the next colour.
Bowyer has tried this railway method by hand and has got it to work, but he still needs to test the method with a printer performing an actual job multiple times before he can know for sure.
If you’d like to try to tackle the task of feeding 20 lines of filament to your print head, you can find Bowyer’s source file on his website.