What are the possibilities of building a 3D printer which uses a cartridge-style material filling rather than the conventional extruder setup? The idea of the cartridge is to eliminate the necessity of taking the material in spool form. My aim is to build a 3d printer which can take materials either in the form of pellets or any other shape. The materials that I want to work with are COC(Cyclic olefin copolymer) and polycarbonates.I have these materials in pellets so need to design an extruder and hot end setup which can directly use these and print . currently I have a Lulzbot Kittaz 3d printer with a single extruder( hexagonal end). Any suggestions where should I start?