This set of files enables you to print your own multicolor filaments (Quad-, Triple- and Dual-Color) and make it possible to create your own colors at home. The result is a fully functional and well calibrated filament that can produce results that are indistinguishable from prints made with commercially bought filament.

the TL;DR:
It works! Just put your favourite colors of PLA in the AMS, open the first print profile (74g for AMS), DON'T CHANGE A THING, press play and have fun :)
No AMS, no problem. Pick the Dual-Color/Manual version and simply switch your filament at the pause and resume the print.

The non-TL;DR version is a very long one. It took me almost 6 weeks to create and optimize these settings towards presicion and reliability, while maximising the amount printed per patch. Starting this project, i had no idea how deep this rabbithole actually is and would like to share some of my insights and findings (e.g. "experimental Aero-PLA") with everybody interested further down. But first things first:

Print Profiles:

ATTENTION: Each print profile comes with 4 filament settings (blue/red/yellow/green - "Generic PLA - Multicolor Filament")  that have their flowrate increased by 4% (from 0.98 to 1.02). It is very important to use these settings - or a version of your favourite setting with it's flowrate equally increased by 4% - and run a flowrate calibration for the printed filament afterwards to get a good result.

ALSO: Watch the position of the prime tower - should you change the printer preset (from P1S to A1 e.g.), the prime tower might change position and end up in the corner, conflicting with the filament printed. In this case, drag it to the centre of the plate.

X1-Users: Switch off (untick) the “automatic flowrate calibration” when sending the file to the printer! This calibration will be overwritten by the embedded filament profile anyways and can conflict with the big patches using the full plate.

There are many different sizes you can print. Each length comes with 3 print profiles. There is an AMS profile that can do 4/3/2 color filament, a separate AMS profile for color mixing and a manual profile that can create 2 color filament and color mixing in one.

The 74g Versions (max A1/P1/X1): These print profiles will create 74g of filament in a very tight loop, maxing out a 256x256mm buildplate. After the print, the filament comes loose easily and can be winded on a spool. (Tip: start with the inside end of the loop)

The 34g Versions (A1 mini): This version uses the full 180x180 buildplate of an A1 mini and prints 34g of filament per patch.

The 15.5g Tester Versions: They are meant to create small samples for you to try out different effects or color-mixes and print exactly as their bigger relatives would. They are sized to comfortably print a benchy or a small test object.

"The Stuck Plates":    - available in 81g and 39g (mini)

...are a very particular brainchild of mine... but what initially started as a thing i tried to avoid turned out to be THE most practical solution and after some tweaking it ended in this "it's not a bug, it's a feature" - situation here:

The filament comes off the plate as one disc but the loops stick together just well enough to easily let go when pulled on from a slight angle. Like this you can feed it directly into the printer without any problems (after 20+ hours of use), the filament can't tangle or twist and you can store it in a very space efficient way. Strangely, these spool holders at the back of P1/X1 printers seem like made for it and there is no loss in quality because of the "unstuck" seams.
I know it looks crazy but give it a try maybe, if it works for you, it's golden. But giving there is a rather small tolerance between sticking not enough (-1%) and sticking too well (+2% from current flowrate - in my case!) there is a good chance it might not work without calibration on all these different printers and filaments out there.

Usage and Multi-Color Effect Optimization:

Flow Rate Calibration: The filament can be used like any other filament and should be calibrated well out of the box but it is still a good idea to run a flowrate calibration with it and create a filament profile for the future. (Bambu Studio > Calibration Tab > Flowrate calibration; or switch on the auto-flowrate calibration again on X1's)

Effect Optimization: To get an understanding of the main mechanic of multicolor filament, take a look at the following pictures:

To optimize the effects of multicolor filament on a print, the only metric that matters is the thickness of your outer wall and by increasing this, you create a thicker layer of a particular color in a certain direction. The differently colored filament that gets extruded at the backside of the wall will be blocked by more material, stopping it from shining through the color that is facing your direction - giving you a much clearer division between the colors you used. You can increase the outer wall width to about 0.75mm without problems even on a 0.4mm nozzle for most prints.

2 or 3 Colors for 0.4mm Nozzle: The multi-color effect is much easier to achieve using a 2 - color filament, more difficult with 3-colors and pretty hard for 4 color filament - using a 0.4mm nozzle (which is probably why 4-colors are not commercially available much). A Benchy printed with standard settings using a 4-color filament will have the colors blended together quite a bit while using a 2- or maybe 3-color filament with the same settings gives good/acceptable results.

However, amazing result can be made printing in vase mode even with 4-color filament and increased (outer)wall thickness. Further changing the nozzle to 0.6 mm or more - along with an increased outer wall width - allows for a Benchy (or any type of print) to have clear divisions at 4 and probably even more colors.

Big Prints: For bigger prints, you can prepare multiple patches of filament and feed them in one after the other. Simply wait until the filament run-out sensor triggers, feed the next patch in and resume the print. There should be a seamless transition between the 2 patches and the filament will be printed in the same orientation as before (i tried but was not even able to force a shift in orientation as the filament always finds it's natural curvature along the bowden tube).

Bottom and Top layer patterns: With changing the bottom or top layer patterns to Octagram Spiral, Hilbert Curve or Archimedean Chords you can create stunning effects on flat surfaces with multi-color filament. The result looks like this:

Left to Right: Octagram Spiral, Hilbert Curve and Archimedean Chords printed with 3-color matte black/white/purple filament. Picture on the right shows the practical application of it. This is an X1 Screen Cover, developed by PharaohMac who made this incredible find. Jump over and give him a boost and a download if this technique is useful for you.

Print Orientation: Depending on the object's shape you are printing, you might want to orient the print, so you get the color or gradient in the right area. As a rule of thumb, using dual-color as an example, the bottom color of the filament will always face towards the bottom of the buildplate and the gradient between the colors will happen facing left and right - fed in externally or with an AMS. Keep in mind that flat walls will only be able to print in a single color blend between the two (same angle along the entire surface), while round wall sections are able to show the gradient between colors. If you want to make sure the colors are facing the right direction, consider printing an Orientation Disc like this one and orient the print in the slicer afterwards according to that.

Color Mixing:

One of the most practical aspects of making your own filament is the ability to create your own unique colors. Is it because this particular color you want simply doesn't exist or you just don't want to buy a whole spool of e.g. pink, knowing you will only use a few grams of it for that one print you want to do.

To print: Load a mixer profile and start with the plate labeled "Mixer 1 of 2" first. It comes with a filament tag to help you remember what colors you used in what order and makes it easier to reproduce that same filament should you run out. After that, feed the filament you just made back into the printer and then start the "Mixer 2 of 2" plate. This will print the same patch again and in doing so, mixes the colors used uniformly throughout the 2nd patch. The result will have slight color variations depending on the angle you are looking at but every mm of filament will evenly contain the intended ratio of colors and using this patch to do other prints, practically mixes the filament a 3rd time, resulting in perfectly uniform colors. Tip: If you want to mix two very opposing or dense colors, instead of printing 4 layers of blue and 4 layers of red, try switching the color every 2nd layer instead.

To change the ratio of colors: You can change the filament at a different layer height in Bambu Studio to get close to your desired ratio. There are 8 layers with individual widths, while the middle 2 layers contain about twice the amount of filament than the first or last layer. To edit them, slice the plate you want to print and go into “Preview” mode:

On the right side of the window you will see the layer scroll bar (picture 1). Scroll to the layer you want to make an edit and right click the slider (+) to open this menue (picture 2). “Add a pause” for manual changes or select “Change Filament” for AMS systems. Note that the entry will take effect at the start of the selected layer before it is printed. When you are done, click “Slice plate” again and check if the desired ratio of colors is close to your needs (picture 3). Repeat if necessary.

To get the color you want: Keep in mind that different colors will have a different density of pigments, meaning they will affect the final color more or less. e.g. to get a standard 50% grey, you want to mix about 75% white with 25% black, giving the black pigments (high density) can easily overshadow the white pigments (low density) in the mix.

There is no real rule of thumb though, every manufacturer of filament uses his own mixture and different types of PLA (e.g. Matte PLA has much more pigments than PLA) will also affect the outcome heavily. The only useable metric, to get a rough estimation beforehand, is the Transmission Distance (TD) that is commonly associated with HueForge-prints and is used to measure how much light can pass through a certain thickness of filament. This metric ranges from 0.1 TD (completely opaque, no light passes through) to 100 TD (like glass, all light passes through) and some manufacturers (sadly not all) provide datasheets for their filament including the TD (Bambu filament spreadsheet available here) As an example typical black PLA has a TD of 0.3-0.6 while white or yellow usually ranges between 9 and 14 TD. In reality though, you will just have to try and there is no precise mathematics behind, but having a general understanding of how the colors behave, will certainly help a lot to produce the desired color.

Winding and Storage:

Except you are printing the "Stuck Plates", you will want to wind up the filament you made on a spool to be able to use it reliably (also in an AMS). It is easiest if you leave the print on the plate and only pick up the inside end of the filament and start to carefully wind it up from there. It's a bit tricky doing it the first time but you will get the hang of it really quick. Watch out to not twist the filament, as this would change the orientation of the colors and pattern of the prints you do later.

To help winding process, i developed a “Spooling Helper” that magnetically attaches to the buildplate and helps to prevent the flipping of individual filament loops when winding it up. You can download it here (https://makerworld.com/en/models/1094352). It comes with a description including pictures that explain the winding process more in detail. Take a look if you are having problems with it, even when you don't intend to print it.

If you need empty spools, check out this design here (https://makerworld.com/en/models/710230). I used the 1/3rd version, they print with only 44g of filament on a single plate, you can put 3 of these on an empty Bambu spool and use them in an AMS without problems.

General information:

Trapped Air: It turns out there is one big obstacle in printing quality filament that lies in the nature of FDM printing itself. While the printhead stacks lines of filament on top of each other, it creates small gaps at the corners between two neighbouring lines containing air. This air gets trapped inside the filament you are making and usually accounts for about 4-6% of it's final volume. This "dilutes" the filament, decreases it's stability and taints the colors slightly milky. To counteract this, the print profiles are set to overextrude by 4% - pushing the excess filament inside the gaps - and also force the slicer to arrange the line pattern in an alternating way (like brick laying) as good as possible.

Like this the air bubbles can be reduced to about 1% - the resulting colors are more fragrant and there is close to no loss in stability even after multiple cycles. (While developing this filament, Orca Slicer implemented a “brick laying” feature that should further minimize air gaps. Once this has been ported to Bambu Studio, the print profiles will be updated accordingly)

Filament Shape: It was surprising to find the shape of filament does not influence the printing quality at all - should you be concerned about the rather oval and uneven shape. I tested square patches of filament without any difference. The only thing that matters is weight per meter and the amount of air trapped in there. There are many intricate things going on in an extrusion process like laminal flow, stress-marks and big groves cut into the filament by the extruder gears. The shape itself is a surprisingly minor factor as long as the extruder can reliably grab the material.

Electricity Use and Sustainability: Initially one of my biggest concerns attempting this project was the obvious “printing filament twice?!? oh, …how wasteful, what a footprint…” - elephant in the room, but thinking about it more, it turns out to be quite the opposite.

A patch of 78g of filament is printed using only 0.18 kWh (or about 3 to 4 cents - measured on a P1S). The rest of it's impact ultimately depends on it's source and further usecase:

• It can be used to create a small patch of this one shade of blue you will ever just need a small amount of - preventing the majority of a whole 1kg spool and it's included supply chain going to waste after a few years.
• It can be used to recycle all these small pieces of leftover filament from empty spools in a workable length again. Print a patch and simply feed these small pieces in after the filament sensor triggered and resume the print until it's finished.
• Want to try out different multi color filaments or just need a small amount for that particular vase you want to make? Again, a whole rack of slightly differently colored plastic could be prevented in many cases.

- OR it can be used to create a thousand articulated dust catchers - just with extra steps. The impact ultimately lies in the hands of the user.

Experimental Aero - PLA:

The fact that air gets trapped inside the filament could be used as an advantage. Trying to maximise this effect with a combination of underextrusion and repeated printing of the resulting filament, the density can be lowered by about 30-45% without sacrificing most of the materials stability. This would lower the density of a solid print below 1g/mm3 and it could become naturally buoyant and float in water. Further more, it could be used for lightweight body parts in mass-critical applications, like airplane/drone parts or e.g. extruder casings.

Note: This approach is contrary to commercial aero-PLA or ASA, which gets underextruded and “puffs” up through a foaming-agent in the extrusion process. This filament would print at regular flow but has thousands of tiny air bubbles trapped inside already.

A big concern although is the layer adhesion that is declining rapidly, seemingly stemming from these air bubbles preventing a strong bond between layers at a certain density. Further testing and optimization is definitely needed - this is far from release - but it could be an interesting implication for self printed filament with many use cases - but simply food for thought at that point.

Although completely functional, this whole project is still considered a work in progress and i will keep updating and optimizing the files depending on feedback. Stay tuned and happy printing! Cheers, fmod ;)