Manual MMU aka Poor Mans MMU for MK4/MK4S (Printer Profiles)

If you want to print small multi-colored objects, you don't necessarily need an MMU. These printer profiles utilize the 'M600 hack', also known as the 'poor mans MMU', allowing you to print in multiple colors without making any hardware modifications to your printer.

I used a similar printer profile for my MK3S+ for a long time and really enjoyed using it. However, when I tried to transfer the settings directly to the MK4S, they didn't work. Since I couldn't find a fully functional profile online, I decided to create one myself.

I've put together printer profiles (.ini) and small test prints (.3mf – open as a project in PrusaSlicer) for the following printer and nozzle combinations:

• MK4S with a 0.4mm HF Nozzle
• MK4S with a 0.4mm Nozzle
• MK4S with a 0.6mm Nozzle

The printer may display a 'wrong filament' warning even if the correct filament is loaded. It's unclear to me why this happens, simply verify and confirm that the correct filament is loaded.

Tested using PrusaSlicer 2.9.0 and MK4S Firmware version 6.1.4+7908.
 

TL;DR - How does it work?

Download the appropriate .3mf file, open it as a project in PrusaSlicer, select your preferred filaments and start printing. The printer will automatically pause when it's time to change the filament. Simply swap the filament and resume printing. You'll quickly get the hang of how it works!

If the test print is successful, delete my test model, import your own STLs into the project, assign the extruders/colors to your models, and start printing again.
 

I'm using a different printer/nozzle combination or want to use more than 2 colors

You can easily create your own profile using the following instructions.

First, create a copy of your normal printer profile, then adjust the following settings:

Printer Settings → General → Extruders Count: 2 (set as many extruders as colors you want to use)
Printer Settings → General → Single Extruder Multi Material: OFF*

* This is crucial to avoid potential issues. In my experience, enabling this setting caused the printer to randomly produce large filament blobs on the wipe tower or resulted in filament jams in the extruder. When this option is active, the printer assumes the presence of a physical MMU (such as a Y-splitter), requiring you to adjust settings like cooling tube position, cooling tube length, and filament parking positions - none of which are needed for our setup.

Printer Settings → Custom G-Code → Tool Change G-Code:

{if layer_num >= 0}M600 N ; change to filament for extruder {next_extruder + 1}{endif}

Instead of performing a tool change, we want to execute a simple filament change (M600). This is achieved by customizing the 'Tool Change G-Code'.

Initially, the printer performed an unnecessary filament change right after the purge line, before starting the actual print. I resolved this by adding {if layer_num >= 0} to the code.

However, there was still a minor issue: after each filament change, the nozzle returned to the printed part instead of going directly to the wipe tower, leaving a small blob of the new filament color on the part. To fix this, I modified M600 to M600 N, ensuring the nozzle moves to the next location after the filament change, rather than returning to its previous position.

Happy multi-color printing! :)
 

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