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.
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.
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). -- http://www.reprap.org/wiki/Repetier_Color_Mixing
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: https://www.amazon.com/STAR-Alchement-Gradient-Filament-filament/dp/B01CNFUH6Q/
Any reason why you couldn't use individual heated reservoirs for filaments of varying primary colors and have the extruder use negative pressure to draw desired pre-melted filament using basically a micro valve system to control flow from each reservoir? Filament would back fill the reservoir only as the chamber empties and the slight pressure difference triggers a switch connected to the feeder.
@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.
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 ;)
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)
Rewriting Repetier firmware to get color mixing working on your
How to install, configure, and use the diamond hotend - tips /
tricks / lessons learned / etc...
My original Bowden extruder design and various ways to mount the
three extruders for your set-up
My universal magnetic effector plate and accompanying hotend mounts
for quickly swapping various hotends. (delta specific)
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...
Configuring color mixing in Repetier and Slic3r to print above
mentioned multi-color models.
Anything else I can think of later that I can't think of now.
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.
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: http://www.reprap.org/wiki/Repetier_Color_Mixing