My wife and I are big fans of the board game Catan, which we call "Settlers" because we started playing it back before its name got shortened. When we get together with friends to play a game and someone emerges victorious, we thought it would be great to have a championship trophy for them to hold onto until the next get-together. Having recently gotten a Prusa MK3S+, I thought this would a great 3D-printing project. But I wanted my trophy to use multiple colors, and a stock MK3S+ prints in only one color. For instance, I wanted it to feature this sheep by cipis from Thingiverse that looks way better in black and white than it would in a single color.
Prusa does make a "multi-material unit" MMU2S upgrade, which I was a little wary of because it has a reputation for requiring a lot of tinkering and hand-holding to get it to work reliably. The problem is that it works by automating the job of loading and unloading filament from the extruder, in doing so it's possible for filament to get stuck and require manual intervention. Filament has to be changed back and forth on every layer, so a single print can require hundreds or even thousands of such "tool changes". But I was excited enough about the idea of printing with multiple materials to give it a try, so I ordered it. It took a couple months for it to arrive, which motivated me to build the rest of the trophy by printing parts using a single material at a time and assembling them with glue.
Non-MMU Parts: Manual Color Changes
I wanted to make a base out of wood filament (like my earlier project, the fan control) and add a pair of dice (gray and pink, like the ones we play the game with). My CAD tool of choice these days is Fusion 360, which works fine for geometric tasks like this.
My plan was to print it in five pieces: the base, each die, each word ("CATAN" and "CHAMP"), and the shelf. For instance, in the shelf I left word-shaped holes:
to be filled by the text which I could print in a different orientation, using a finer nozzle (0.25mm instead of 0.4mm) to get better detail on the letters.
But even without the MMU2S, these parts weren't entirely single-material. PrusaSlicer lets you insert "color change" instructions between layers, so that the printer will pause and let you switch from one filament to another. I used that on the base and the shelf to insert little gold stripes into the wood:
I know those are some pretty gnarly layer lines... not sure what's up with that. Anyway I also used this color-change trick when printing the words, to make the letters gold but the back black.
For the white pips on the dice, I thought I might use the MMU2S but it still hadn't arrived. So I just printed the dice with a little extra depth in the pips, so I could fill them in with white caulk. That's what I did for the gray one anyway, it worked okay but it was very sticky and difficult. So for the pink one I used soem white latex paint I had left over from painting my house, and that worked much better.
Multi-Material Unit
The only remaining part is the sheep, and for that I had to wait for the MMU. It comes as a kit. You can't elect to have them assemble it for you like you can with the printer itself, probably because they figure if you can't handle building it from a kit, you certainly can't handle the tinkering required to get it to work. Like the printer, you can choose between two colors: orange and black. Orange is my least-favorite color so I chose black, but then I realized that the black parts would make it too difficult to see what was going on inside in order to diagnose and fix problems. Luckily, Prusa provides digital STL versions of all the parts so you can print your own. I ordered some white PETG Prusament filament and did exactly that. It turned out pretty sassy, IMHO.
I didn't even bother assembling the buffer unit (for keeping the 5 filaments from getting tangled) because everything I read about it said that it doesn't work well. I was only planning to use 2 at first, so I decided to just give them some room and take my chances.
I ended up having to intervene at least about about a dozen times, I think mostly due to the fact that the PTFE tube that runs from the MMU2S to the extruder has a very small inside diameter (2mm) and the filament would often get stuck inside when loading. So I ordered an alternate tube (3mm inside diameter, 4mm outside diameter) to try next time. But in the end, with a bunch of manual interventions, I was eventually able to get a nice-looking sheep!
If you look closely you'll see that he's bright white on the bottom, but most of his wool is kind of light gray. That's because some of the layers require using some black filament (the gray ones) and some layers only have white. I guess that's a hazard of using white filament in a multi-material print; if I had to do it again I'd change the model to include a little bit of black in the bottom in the middle of the model where you can't see it, so that all the layers are equally dingy.
Questions or comments? Email me at .
2021 Apr 17