MMSU

MMSU - Multi Material Switching Unit 

If you like the project, you can support me here: https://coff.ee/mayster

Hey, I’ve created the MMSU, which is based on parts from the MMU PICO. It’s a side project of mine, but it turned out so well and works so smoothly that I decided to share it. I hope you’ll like it! 

MMSU has a NEMA 17 stepper motor which serves as the second extruder, and a 180-degree servo that selects which filament is currently being pushed by the stepper motor. Personally, I have connected this motor directly to the mainboard—both the servo, which I control using a free Neopixel port, or if available, a free port for the BLTouch servo (important: make sure to power the servo properly so it can draw around 2A—I use a separate converter for this). The stepper motor is connected to a free slot for a TMC2209 driver. I use RepRap firmware and a BTT Octopus board. I don’t have any config files for Klipper or Marlin the MMSU project is based on the MMU Pico:
https://github.com/lhndo/LH-Stinger/wiki/Pico-MMU,
which uses the same motors and works on a similar principle. There are different boards for the Pico available on AliExpress that will work with MMSU.

The MMSU features side tension adjusters that allow you to set the clutch pressure against the filament. To insert or remove an adjuster, you need to unscrew the side locking screw and set the arrow to position 0.

I’ll try to provide an instructional video showing how to assemble the unit, but I believe the assembly process is very simple and enjoyable. On the other hand, programming and calibration can be a bit more challenging. However, you can use the same macros as for the PICO MMU — just keep in mind that the servo moves in 30-degree steps, and 190 degrees is considered the neutral position with a 1:1.2 gear ratio. So, if we want to select filament No. 2, the servo must move to position 30; if it's No. 3, then to 60, and so on. This is because the angle between individual segments on the camshaft is exactly 36 degrees, and the servo has a 1:1.2 gear ratio, meaning 1.2 × 30 = 36.

This differs from the Pico MMU, where the camshaft angle is 33.3 degrees. 

That is the only difference in the software that distinguishes it from the MMSU.

List of parts:
1. [The same as Pico MMU]
- Nema 17 Stepper Motor [MAX 48mm]
- Servo Motor [180 degrees] for me it was MG966R
- 5mm Flat shaft [2x 132mm]
- BMG drive gears 8mm [6x]
- GT2 6mm Belt [~500mm]
- Ecas PTFE connectors [12x]
- Bearings (5x11x5) [5x]
- Bearings (3x8x3) [8x]

2. [Different than Pico MMU]
Bolts:
- M3 L8 [2x] Socket Head OR (L10 Flat Head)
- M3 L12 [6x] Flat Head
- M3 L14 [23x] Flat Head
- M3 L16 [4x] Flat Head
- M3 L20 [3x] Flat Head
Heat Insert:
- M3 L4 D5 [60x]
PTFE
- 2,5mm