Tool changing 3D printers are hot. The idea is that instead of switching filament, you swap out hot ends or other tools. That isn’t a new idea. However, most tool changers are expensive. [Engineers Grow] has one that is simple and inexpensive, relying on the printer’s own motors and some clever mechanics.

The first step was to make a modified extruder that allowed the filament to load and unload. The first attempt didn’t work well, but that is the nice thing about 3D printing — it is easy to try again. There is only one extruder, which is good from the standpoint that you don’t need a control board with many outputs and you avoid the expense of multiple extruders.

The next step is a spring-loaded filament guide to load and unload the new extruder. That didn’t work at first, either. Worse, fixing the problems required yet another redesign of the extruder.

The hot end holds with magnets. This isn’t always as stable as you would like, but it should work, especially with the pin alignment scheme. The tool plate engages with the head and moves to the side to break the magnetic grip. A bracket works the levers to handle the filament changes.

Everything seemed to work when manually moving things around. Macro development eventually wound up with everything working with two heads after troubleshooting a few issues. Of primary concern is the hot ends are not rigidly held, and docking wasn’t always repeatable. However, this is just a prototype and it does work. It only needs more rigidity and repeatability.

Outside of the printer itself, the changer costs about $100, although that will change depending on the number of extruders. Since the whole thing is printer-specific and not fully functional, there are no models or code — and it sounds like [Engineers Grow] plans to make them available only if you have a membership. But the idea is sound, and there is enough information in the video for you to do your own experiments using this mechanical-only design. Let us know what you come up with.

We’ve seen passive changers on CNC before. Many of the others we’ve seen use electromagnets. Our own [Sonya Vasquez] did a take on this with Jubilee.