Universal Bowden Dual Extrusion with 1 Stepper, 1 Nozzle, and No firmware modification

thingiverse

This is a dual-extrusion system designed specifically for Bowden-style 3D printers. Installing it doesn't require any firmware updates to the printer itself, but you will need an Arduino that can handle one servo motor. The key difference between this setup and existing solutions is its use of two separate extruder bodies, each with adjustable idler tension, which switch seamlessly between them. This setup offers a level of control over the extruders that other solutions simply can't match, relying as they do on a single servo motor to manage tension.