Multimaterial printing usually means extra motors, extra extruders or a big box of hardware sitting next to the machine. HatChanger takes another route: instead of pushing filament through a long tube, it swaps only the top part of the extruder, called a hat. Filippo Pisano describes the concept as blending ideas from Stealthchanger and INDX, and the goal is a cheap alternative to more elaborate multimaterial solutions.
The parts list is remarkably short: a few printed pieces, M3 pins and magnets. No additional steppers, servos or extruders are involved, so the whole swapping mechanism is passive. Filament travels through a PTFE tube and an ECAS fitting, and a sensor sits inside the modified front body of a Stealthchanger. Loading is done by hand; after that, the toolhead loads and ejects filament as the extruder gears and the z axis move in sync. The machine shown is an enclosed Voron-style CoreXY with two docking stations on the top frame and a yellow Stealthburner-style head with a nozzle LED. The hat on display is already the 30th iteration, each one costs under four dollars per lane to print, and a 300mm Voron can hold six or seven lanes.
Several details stand out to me. Macros drive the changes and include sanity checks that pause or stop after failed swaps, and an AFC integration makes infinite spool functionality work out of the box. This is an early alpha proof of concept that can already print, which the maker considers the most important outcome. Since it uses a single nozzle, the usual drawbacks like purge towers and slow changes remain. Reliability has not been thoroughly tested yet, and the inconsistent filament angle case is still unresolved. The maker also wants the system tried on different printers, and the files are open source on GitHub for anyone who wants to help.
Project by Filippo Pisano. Watch it on their YouTube channel: