# What is stopping us from mixing 3D filament colors in an Extruder?

This came up in one of my groups today. That we could not color bend, or mix 3d printing filaments. I have researched but I am not finding anything talking about Plastic mixing in an extruder.

Why is it that we cannot take say a Diamond hotend, or a hotend with 5+ inputs, and mix any color we want? (assuming all the same type, ABSm, PLA). I think it would be interesting to at the least get a gradient effect on prints.

The best I have seen is natural plastic and a marker system. Or a powder / advanced / out of hobbyist price range process that sprays ink. The only Color Bending I know of is with Recycled plastic that uses multi color. Not quite what I am looking for.

Thanks!

• Probably better (in theory) to build your own filament production tool, similar to those which 'recycle' plastic crud into new filament, and use that to generate each color you want. Then for a multicolor object, swap filaments at appropriate levels. – Carl Witthoft Aug 23 '16 at 14:55
• Maybe I missed the point of the question, but you can totally do color mixing with a diamond hotend to produce a range of colors -- right now I think they make a 3 way one that allows Cyan, Magenta, and Yellow (like a traditional desktop printer). -- reprap.org/wiki/Repetier_Color_Mixing – BrainSlugs83 Oct 27 '16 at 23:24
• Though, if you just want to do crazy gradients, you can just buy filament that gradually cycles colors every so often -- it produces neat results: amazon.com/STAR-Alchement-Gradient-Filament-filament/dp/… – BrainSlugs83 Oct 27 '16 at 23:26
• @SteveW - Two problems. You would 'cook' the idle plastic, and there is no suitable vacuum source to generate your 'negative pressure'. Extruders work under high pressure to achieve good flow rates and print speeds. – Sean Houlihane Mar 23 '18 at 8:27
• On the 2018 Didacta in Germany I was able to see an almost marketed "full color" printer, that used ink cartridges and uncolored, natural PLA to directly embed color into the print: a XYZprinting DaVinci Color, that was called marketed as the first one to use this combination. – Trish Sep 16 '18 at 10:00

I just started with google and phrase "3d printing color mixing" and on the first place (in fact first two were valueless adverts) I got this Instructables - DIY Full Color Mixing 3D Printer.

How it works?

It uses magenta / cyan / yellow filaments and mixes it while printing with Diamond hotend.

It definitely does what you are asking for and it's exactly the same idea you come up with ;)

Overview

1. Getting the controller board ready for three extruders... I hacked a RAMBo board to drive three extruders, however, you can use any board you want... (most people use a RUMBA due to it having all the pins/components needed for 3 extruders native on the board)

2. Rewriting Repetier firmware to get color mixing working on your machine.

3. How to install, configure, and use the diamond hotend - tips / tricks / lessons learned / etc...

4. My original Bowden extruder design and various ways to mount the three extruders for your set-up

5. My universal magnetic effector plate and accompanying hotend mounts for quickly swapping various hotends. (delta specific)

6. How to design multi-color models and making STLs that can be exported and used as a individual STLs or combining them into an AMF file for slicing...

7. Configuring color mixing in Repetier and Slic3r to print above mentioned multi-color models.

8. Anything else I can think of later that I can't think of now.

9. Comprehensive overview of Quantum Mechanical Entanglement as it pertains to multi-color printing (just kidding, I don't understand that... But I will cover multi-color printing throughly)

• Any other day this would get the selected answer, as it does what I wanted. Though with so many good answers, I will have to go with the direct question of what is stopping us. That said thanks for the link! I don't know why that did not appear in my googling. – StarWind0 Aug 24 '16 at 16:22
• Perhaps, the actual answer is "nothing is stopping you". -- This is exactly what the diamond hot end is for. -- Here's the reprap wiki guide for doing CMY color mixing with Repetier: reprap.org/wiki/Repetier_Color_Mixing – BrainSlugs83 Oct 27 '16 at 23:29
• I would say this could be expanded on. That said this is the best solution at this point. – StarWind0 Nov 13 '16 at 4:53

The three in one print head is the closest to your concept of gradient printing and does some nice transitions. But does not meet your color mixing.

Which I assume your looking for there is something like blue and yellow making green and by varying those percent getting shades of green. The three in one head does get close to a dot by dot transition.

I have since I first seen the crowd funding request for the Palette been dwelling on this same concept true color printing in 3D like a laser printer prints paper. The Palette Palette web site is moving closer to color mixing or fast transitions for multiple colors and again can make flowing color changes but still not a true mixer. But is is still color striping. I want one for simple sake of switching color spools with out pulling off and re-feeding filament. And for my Rostock allowing two to four color switching with a single head.

For many months I have pondered taking their unit for its software ability to pre-switch colors and feed it with a three color head.

My plan that I have been mulling for months now is cross mixing of their color switcher with five into one extruder with not a print nozzle but a 1.75 or 3mm filament production nozzle to produce a software timed output based on desired print color effect. Then feeding that to your single nozzle printer would make a true multi-color mixer.

As I was thinking on assembling myself this and put it out there for use, but first I hate doing a lot of programing, second I have health issues slowing me down, third is way to many project. So here is a concept.

• Five extruders, CYM-BW cyan, yellow, magenta, black, white
• These feed a forming nozzle 1.75mm out into a pfte tube going to printer extruder
• The forming nozzle is several centimeters long and has it own secondary heater. The interior is milled with a 5 in to a swirl wall (like a mixing nozzle on epoxy).
• Color filament feeding three of the nozzles are your primary colors set in the center of the color range.
• PrintCOLOR(C, Y, M) command set basically like other color sets 0-255 range. Difference being is 0 is white filament, 254 is black filament, 255 is no filament, 127 is pure color. With 1-126 gradient mix of white and color, 128-253 gradient mix of black and color.
• Feed by extruders into mixer must total extruder speed of printer, which is where need for PrintCOLOR(C, Y, M) programming is required. For instance making green out of C and Y. PrintCOLOR(127, 127, 0) would need half speed blue and half speed yellow.

So who knows maybe some one like the makers of Palette or some crowd funder can run with this. I think it is fully do able.

Three color diamond head can not produce WHITE by mixing. To print white requires dropping one color to substituting in the white. And it requires major modification to many printers to add. The CYM filament picked for use on a diamond head alone sets the maximum darkness allowed. Having ability to mix white and black to CYM solves this issue. 5 color CYM-WB is minimum to get a true mix.

A Kickstarter campaign just finished for a full color 3D FDM printer, the RoVa4D Full Color Blender 3D Printer. It used CYMK printing and includes black and white filament for 5 color filament feeds, plus additional feeds for flexible and support filaments. They raised \$216k against a target of \$25k.

The company that is doing this has other printers in production, I believe. This one adds the color capability. It's planned for 12"x12"x18" print volume.

I am not associated with the project.

As darth_pixel points out, people have had limited success with feeding multiple colors into a diamond hotend and mixing them, but I would argue this is not truly what you're looking for.

The problem is that when feeding multiple filaments into a diamond-style hotend, the colors do not naturally mix completely: if you look at an object printed this way the color changes with the angle you view it from.

This would not be fundamentally impossible to overcome: you could make the melt zone longer, and possibly introduce something to promote mixing (like a spiral path for the molten plastic). However, this would greatly increase the force required to extrude and make retraction near impossible. Both of these issues would reduce print quality.

The results would also not be very good, as you'd need a long purge between colors, limiting the number of distinct colors you can use in a single model while keeping the print time acceptable. Moreover, given how limited the resolution of FDM is you could not make very detailed graphics either.

Over all, you're much better served with painting or assembling parts printed in different colors.

Given the limited potential for color printing in FDM and the mentioned obstacles to building a color mixing hotend, I think it is natural nobody has built one (*) but that doesn't mean it is fundamentally impossible.

(*) There have been some attempts, many on Kickstarter, but none have been truly successful.

• Another problem is that it takes too long to switch from one color to another, since the old color has to be purged. A comment on the guy's YouTube video says it takes 100mm to fully switch colors. That would add up to quite a bit of waste. – John Sensebe Aug 24 '16 at 13:29
• So it comes out like toothpaste? – tuskiomi Sep 14 '16 at 19:08
• There's certainly a lag between color changes, but from what I've seen, the color mixing does happen correctly. -- As for the "purging" that seems like it can be accounted for / calibrated, to the point where the slicer can just use partially changed colors for the infill... – BrainSlugs83 Oct 27 '16 at 23:34

Branching off of TomvanderZanden's answer, this process cannot easily be done with an extruder alone. To properly color polymers, a pigment must be added during the initial treatment process (otherwise applied during any heat treatment). These pigments do not necessarily allow a simple red + blue = purple process to change the color for many reasons including:

• Polymer Transparency
• Polymer Refractive Index. Kinda goes with Transparency, but how light interacts with the surface of the material might set how people perceive the color.
• Polymer Quality (how "virgin" it is). Non-virgin material may mean that impurities absorb the pigments easier or refract light differently, giving a different color.
• Pigment Quality. If a cheaper pigment is used, it may not bind as well with the polymer.
• etc

The above variables may hinder the desired color in even a single batch of plastic, let alone trying to mix two together. Also consider, that the pigments in each filament spool will be deluded as it has already bonded to the current filament. Review a phase diagram for an optimal temperature and time to introduce pigments.

The best case would be to create your own masterbatch and somehow re-color the filament as you would in a normal manufacturing process.

If you clearly observe the geometry of the print it has printed in different colours .the part is designed in such a way that it has the small height gap between the each colour but we cannot seen this gap in one projection plane.. We can print only in direct drive extrusion .by changing the filament of different colours without pausing the print by immediately changing the material . It is printed in single nozzle. The above image clears your doubt.it is designed with different heights.

• Hey Ajay, the question is closely related to the mixing of colors, not the use of multiple colors. – StarWind0 Feb 19 '18 at 17:01