Dual-Coloured 3D Printing

Updated 03 February 2021

The eternal question of ‘does it print in more colours?’ is often one of the most common community desires. And yes you can! One of the best ways that this need is delivered is through dual-extrusion printing. Dual-extrusion printing is the process of 3D printing with multiple filaments in a single print. This means your printer will have nozzles capable of depositing filament from two separate material spools one by one. Dual-extrusion opens a world of composite materials, greater capabilities for supports (which hugely expands the possibilities for your own 3D printed components) and crucially for this video multicoloured prints. All at your fingertips.

This guide is going to focus on dual extruding printing two of the same material that only differs in colour and improving the final printed result. Contents of this guide can be seen below.

- Technologies Overview
- Material Choice
- Hardware Set-up
- CAD Design Process and Tip to Improve the Sharpness of Colours Transitions
- Setting up Models in Slicing Program
Acknowledgment

The process to 3D print multiple colours is the same no matter what slicing software you use however this guide will go through the workflow in Ultimaker Cura. There is an Ultimaker Cura Overview Guide which is a great reference point if this is your first time encountering Cura and you want to hit the ground running. Put simply Ultimaker Cura is a software which allows you to turn the computer file of your design into a recipe for a 3D printer to follow. It is available online and is a completely free software used by over a million users worldwide.

As always if you have got any questions, queries or things you'd like to see added please let us know your thoughts!


Technologies Overview

Dual-extrusion capabilities are found on Ultimaker S5 3D Printers and Ultimaker S3 3D Printers as stock standard. Also, other Ultimaker 3D printers can have this ability mounted and installed by a capable user but experimentation would be required to run optimally. Ultimaker S5 and S3 Printers have dual-extrusion heads with two nozzles where each filament is deposited through its own nozzle respectively. See below of an image of an Ultimaker S3 Working hard dual extruding.

Dual Extrusion
 

There are different ways and technologies to get multiple colours on to a single part when dealing with Fused filament technologies. It can be done simply by stopping, changing out filament spool for a new one with different colours and then un-pausing the print. This will limit you to colour changes in the Z-Axis. There is a machine called the M3D Crane Quad. This features a four-in-one-out extruder head referred to as a Quadfusion. This extruder has four filaments coming into a single nozzle and has the capability to produce over 50,000 colours however each colour change the nozzle needs to be purged. Another technology that is doing the rounds is the Mosaic Manufacturing Palette 2. This is a device that can be set up for any single nozzle extruder. This can take 4 different filaments and then cuts and reform them into a single strand which then goes through into the 3D printing system. It reads information from the G-code and predicts when certain colours are required.

If money is no object and your sole interest is beautiful, coloured parts of the whole rainbow the best bet is from Material Jetting technology. The technology works similarly to traditional inkjet printing, but instead of jetting ink onto paper, a print head jets liquid photopolymers onto a build tray where each droplet cures in a flash of UV light. The PolyJet Multi-Color like the Stratasys J750 is the best set up currently for multi-coloured prints but it does require multiple post-processing steps with multiple propriety machines to improve both the strength and colour of the final piece. The final results do speak for themselves.

PolyPrints are out of this world!

 


Material Choice

Back to Dual extruding with Fused filament fabrication. Now specific materials can bond well with some materials but not well with others. As dual-extrusion printing often occurs with different filament materials it is worthwhile to understand and know these relationships between them. For Ultimaker printers this dual-extrusion capability is found on Ultimaker S5 3D Printer and Ultimaker S3 3D Printer as standard. Below is a chart in relation to Ultimaker dual-extrusion printing, displaying compatible and experimental material combinations. Not all 3D printing machines are made equal but the information in the table below is generally applicable no matter what dual extruding 3D printer you have. Here is a link to a range 3D printing filament.

Compatible is the go!

 

3D printing filaments have a wide range of properties and successful prints employing multiple materials will be harder to achieve the more extreme the material properties differences. Printing two completely different materials is normally not good engineering practise as bonding between them will often be weak and inevitably produces poor prints. For the best success, it is crucial to know the interactions between different materials when utilizing dual-extrusion heads. 

 


Hardware Set-UpTinTin Rocket!

For Ultimaker machines to get multiple colours on a single print without stopping and exchanging filaments midway is done by using the dual extruder and setting up the Cura settings to make one material to go one place and another material to go another place.

Now make sure you have the correct print core installed for your materials. Ultimaker machines with dual-extrusion come with AA cores and BB cores. BB cores are used for support material so will not produce a good result with PLA or other structural materials. Use the right print cores for the right materials and good results will follow. Thus swap out those BB cores for AA cores of the same diameter. A great tutorial all about this can be found here all on Ultimaker Print Cores. 

Make sure your X-Y calibration is done. This is a calibration process which on any dual extruder 3D printer will have. This is done to make sure both nozzles know exactly where they are in relation to each other. Doing this will result in the sharpest cleanest result. While you are up close and personal with those nozzles give them a good clean and make sure they are extruding correctly. A great guide to check out for all on cleaning nozzles and maintaining 3D printers can be found here.


CAD Design Process and Tip to Improve the Sharpness of Colours Transitions

Each colour needs its own unique CAD model. This means you either need to design each colour as a unique part or separate a full-body into multiple parts. So keep this in mind when designing your parts. Below you can see two models which represent the Red part and the white part of the Rocket from The Adventures of Tintin. Jump to the Acknowledgment Section to find this model and print it yourself. It is by overlaying these two models in the slicing software and then slicing it like that which enable dual coloured printing with dual-extrusion to work correctly.

Tin Tin Rocket in Fusion 360. Left is the white section Right is the Red Section

To increase the crispness between colour transitions, have a small relief or trench between sections when looking at the X or Y plane. In the Z plane ensure that there is no gap between colours and that they do not overlap (unless you want to mix the colours together which is possible, but this guide will focus on making sharp transitions between colours) and also have that trench. The trench is less than a millimetre deep and imperceptible from a distance but makes a huge difference. Below is a close up of the rocket with the taper/trench visible between the section. It is subtle but makes a huge difference in the final result. Very much worth the effort.

Trench Between Colours 


Setting up Models in Slicing Program

Make sure to overlay the centre of the two models perfectly on top of each other. Below is an example of me doing this for the rocket. What position they are here is the position that the 3D printer will print it in. This can become tricky if rotating the model is required but take your time and the best result will occur. Make sure to zoom right in and double-check all the positioning.

Process

Now make sure one model is being created with one filament and the other model is being created with the other filament. This is done by selecting the model and clicking on the corresponding filament symbol on the left toolbar. See below for details of this in Cura. Cura will also give a visual colour indication across the surface of the model when filament colours or types are changed.

Filament Selector 

Most important is to use a purge tower and an ooze shield. Using both in combination enable the best cleanest results. Both methods are techniques a 3D printer use to prime the printing nozzles for the next layer. Without either a purge tower or an ooze shield, you will end up with stringy hair-like filament covering your desired component and have blemishes on the surface. Purge towers are also referred to as prime towers and are an additional print created on the build plate made to the height of the component desired. Ooze shields are a one-layer wide wall that encase, but does not touch, the final model. For more information of these and the settings I use for them check out the tutorial Purge Towers and Ooze Shields.

Top of Rocket encased in Ooze shield with Prime Tower in back
 

Now to get the best results out of your 3D printer check out Improving your 3D printed models guide found here. Once you have found a profile and setting that crushes make sure to use that exact same set up for both print materials. This will enable consistent results across the model with matching layer lines. Ultimaker Profiles for PLA and ABS automatically work. Colour differences between the same filament would change the material properties but the effect is negligible. Also, minimise supports around surface areas. Support structures can mark the final surface and this will affect the final result. See below for some different angles of 3D printed d20 Dice. The sides which I used support have a worse surface finish than the side that did not need support. This dice also demonstrates the advantages of Dual colour surfaces on positive slopes and not on overhung sections. These had ooze shields and purge towers as well.   

Dice Ting


Acknowledgements 

This TinTin Rocket is an absolutely gorgeous model and all credit goes to an excellent Frenchman Laurent Alcantara. The greatest model of this rocket in existence, it'd make Hergé proud. There is a really neat 3D printable sanding block designed by Laurent in the Thingiverse profile as well.

Shoot for the Stars!

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