[Teaching Tech] sprung about $80 or a kit to add dual extrusion to his 3D printer, plus another $20 for an accessory kit. He did get it to work well, but it wasn’t without problems which he covers in the video below.
The design of the head uses a servo to swing two hot ends to — in theory — the same point. Each hot end has an ooze shield, so you don’t need to deal with that in your G-code by building a priming tower. However, there are some requirements for your printer.
For one thing, the carriage is made to fit on a 2020 V Slot. You might be able to adapt it to something else. The assembly is pretty big. In the video, it seems this reduced the build surface in the Y and Z axis by 50mm. The auto level sensor requires a metal bed, although you could fix that pretty easily. Of course, you also need a controller board that can handle 5 stepper outputs.
One thing [Teaching Tech] mentions that should be obvious is that you need a Bowden extruder. The kit comes with one, and presumably, you’ll use the other from your existing setup.
Most of the kit is pretty standard fare, but the servo bracket and high-torque servo is really the secret sauce to this dual extruder. However, there were quite a few finicky issues with putting things together and calibration looked like a lot of work, too.
It didn’t help that the servo died and it sounds like that happens often. It may be related to driving the servo beyond its stops. The bed leveling sensor also died. Still, when it was all done it did seem to work well.