Reducing Poop On Multicolor Prints

While multicolor printing eliminates painting steps and produces vibrant objects, there are two significant downsides; filament consumption and print time. A single-nozzle filament printer needs to switch from one color to another, and doing so involves switching to the other filament and then purging the transition filament that contains a mixture of both colors, before resuming the print with the clean new color.

[teachingtech] tests out a variety of methods for reducing print time and waste. One surprising result was that purging into the infill didn’t result in significant savings, even when the infill was as high as 50%. Things that did have a positive effect included reducing the amount of purge per transition based on light to dark color changes, and printing multiple copies at once so that even though the total amount of waste was the same as a single part, the waste per part was reduced.

All of the tests were with the same model, which had 229 color changes within a small part, so your mileage may vary, but it’s an interesting investigation into some of the deeper settings within the slicer. Reducing filament waste and print time is an admirable goal, and if you make your own extruder, you can turn all of that purge waste into various shades of greenish brownish filament.

25 thoughts on “Reducing Poop On Multicolor Prints

  1. Well, reducing this waste is easy – if you don’t want the waste, don’t do multicolor prints with many color changes on a machine that has a single extruder and has to change filaments – like the Bambulab ones do.

    While that design certainly does work it produces ridiculous amounts of waste for these types of prints, often 2-3x the amount of plastic that ends in the actual object being printed. That’s just economical nonsense. If multicolor prints are to be done on a regular basis then do get a multi-extruder/toolchanging machine instead.

  2. Couldn’t you eliminate all the waste by printing something that doesn’t care about colour at the same time? (e.g. something that’ll end up hidden, or something that’ll get painted anyway)

    1. Yes, you can see in the video, that you can enable purging into inside of an object.
      But it didn’t helped much (probably because the used model is small so the purge still must be done “external”)

      1. It’s literally in the video. Bambu’s slicer can use the color change purge as infill or support. In this case it didn’t make sense because the print is very small, but I can see it being enough for larger prints.

  3. Can someone with some experience weigh in: holy cow 229 color changes!? The part has like 3-4 colors. Is this typical? If changing colors results in so much waste surely something is way wrong about this implementation.

    1. 3-4 colors times how many layers? If a layer has 4 colors thats 3 transitions on that layer alone. Adds up fast. Its only WRONG if you cannot tolerate or manage the waste.

      This is a wasteful hobby. I can hand sculpt, mold, and cast a dozen copies of MOST printed objects in the time the machine takes.

      What percent of your prints are support WASTE?
      Should everyone abandon FDM entirely? If supporting models results in so much waste surely something is way wrong about this implementation. /s

      A significant portion of 3d printing hobbyists print nothing of real worth. They are churning out tons of garbage. Printing every random object they find kewl on whatever model repository they are enamored with isnt any better really. Should the slicer refuse to slice until the prints have been justified? or should be just let people enjoy their hobby?

      Not everyone can afford a mimaki, and I dont see them releasing a budget model anytime soon.

      1. Im with you up until the point where most 3d printer people are just producing waste. By that logic, most painters are producing waste too – but the time doing it is enjoyed. You put the awful drawing your child made on the fridge not because it is a worthwhile priceless piece of art but because it has sentimental value. 3d printing to a lot of people is an art – and that’s fine.

        As for the waste I really wish there were more recycling joints for 3d printing scraps. Even the spools are usually 200g of unmarked mystery plastic that municipal recycling won’t touch – even before you print ~15% is waste. So dumb

        1. Yep, I mostly print without support and have a quite good yield regarding filament waste.
          But I have about 30 empty spools lying around. I would be more happy to recycle these than the remaining filament :D

    2. Well…. It works on a $1500 machine…. Yes its wasteful, but its automatic. If you are able to implement it in a better way than bambu, you really should really do it because people would buy your machine.

        1. Why are so many people raising this idea as if it isn’t already implemented? You don’t even need to watch the video, it’s mentioned in the second sentence of the second paragraph, literally the first method that’s described in the article (that’s what purging into infill is) – as already described by others, this doesn’t get rid of the problem in models that don’t have a lot of infill

      1. E3D’s Toolchanger isn’t that much more expensive than an X1C with AMS, and there’s plenty of IDEX printers around that can do 2 colours, both with much less purging since they really just need a tiny reprime instead of a full colour change each time

  4. Some colors transitions are faster than others but still waste the same poop. And some transitions take longer resulting in remaining color bleed after the poop. Bambu needs to add a purge sensor.

    While I currently prefer using a color indiscriminate secondary “purge print”, I still find that upon returning to the main multicolor print there are sometimes streaks remaining.

    Having a “port” that the nozzle could dock to and then extrude, allowing the melt to pass through a fan or two worth of cooling and resolidification until a camera based sensor determined the purge was complete and said “WHOA!” would be ideal. Id much rather a pile of purge threads than lumps. In an ideal world, a cutter would automatically trim the lead, transition, and follow sections. In theory this would reduce the amount of “muddy” toned recycled filament.

    Bambu really should throw some R&D into coming up with an idealized “purge filament” for PLA. If they could come up with a cheap polymer that wouldnt bond/blend with PLA, that would both push out the PLA and its pigments, and would also be quickly pushed out by the next round of PLA, it would be a real game changer.

    1. a couple years ago i saw someone doing color transition calibration. they tested all their color combinations in both To and From transitions and used those values in the slicer. a bit laborious to check all the combinations, but the were able to drop most of the transitions waste to under 50%. dark to light transitions obviously were the worst.

      1. Thats why Im saying, “camera based sensing.”
        no need for any labor, no testing and charting, no relying on the pigment from supplier X to stay the same from one batch to the next.
        I was surprised that the X1C didnt do this already. It has been one of my few disappointments.

  5. Someone made a code with a change to the original bambulab change filament routine where the extruder retracts 20mm before cutting and changing filament.
    Therefore every filament change, no matter the settings, has 20mm less filament waste.
    The slicer doesn’t recognize the change in code so the reduction won’t show in the slicing results.
    It only shows in the actual waste produced.
    The code is available for download on printables.

  6. The younger store clerks insist I don’t need a bag. Reduce, Recycle, Renew and all that. ♻️
    Yet the stores dump tons of unsold phone cases made of … plastic. (Almost EVERY SINGLE model of phone needs a unique case and stores stock all these in multiple styles and colors to meet consumer demand.)

    1. Well, the young store clerks aren’t really in a position to force their employers to adopt a less profitable on demand low stocking policy but are in a position to discourage single use plastic bags, and using both results in more plastic waste than only having the phone cases…

      Don’t let the perfect be the enemy of the good. It’s absolutely right to advocate against all forms of plastic waste (although I would argue that increasing the effective lifespan of a phone would substantially decrease total waste a lot more than decreasing case availability since the cases are an important part in keeping phones alive for most users and you only need one case for each new phone you buy), but the fact that some of them still exist shouldn’t be a reason to fight against reduction in other areas…

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