The Ultimate Guide to 3D Printing in Color

Most 3D printing technologies can only print in a single color. To get multi-colored prints, it usually requires that you use paint or other post-processing techniques to add color afterwards. However for complex objects, painting afterwards may not be an option and the only solution is to print the part in color. In this tutorial, we’ll be going over 5 techniques for adding color to your 3D prints. We’ll start with lower cost options like filament swapping and dual extrusion and work our way up to expensive and industrial options like PolyJet and Binder Jetting.

Filament Swapping

Filament swapping is a technique used in FDM printing that allows you to use different colors for different layers of your model. It’s a relatively simple process and can be done on most FDM machines:

1. Pause the print where you want to swap out colors
2. Raise the nozzle 20mm in the Z axis using your control software
3. Retract the existing filament
4. Extrude the new filament until you see the color change
5. Remove the extruded filament
6. Lower the Z axis 20mm to the original position
7. Resume the print

This method is great for things like logos or plaques with extruded text. The bottom portion of the model can be printed in one color and the color is then changed to highlight the upper portions of your model. This can be done as many times as you’d like but can be a bit tedious and is often challenging to get right.

Filament Dyeing

Filament dyeing, much like filament swapping, allows you to color different layers in your model. This technique works best with nylon filament. Nylon is notorious for absorbing moisture and needing to be kept in a dry or sealed environment, but it’s this property that also allows it to readily absorb fabric dye. We’ve found that Rit dye works best for this process. For a more in depth tutorial check out our blog 5 Steps to Tie Dye Filament. We’ll give a quick rundown of that process here.

1. Wrap your filament into a coil and secure with string or zip ties
2. Boil water and mix it with your Rit Dye
3. Place a portion of your nylon filament in the solution for up to 10 minutes
4. Remove and repeat for the remaining sections using as much color as you’d likeThis process can produce some pretty impressive results, but you have very little control over which sections adopt which color. Many nylon filaments require high extrusion temperatures upwards of 245C which is hotter than many hotends can handle. For a lower temperature nylon, check out Taulman’s Nylon 230.
   

   Multi-Extrusion

   Printers with multiple extruders have historically proven challenging to get to perform reliably but the technology continues to improve. Dual extrusion printers function by having multiple extruders feed different types and/or colors of filament to a hotend or hotends. There are two main techniques for doing this.

   The more popular includes two or more extruders and two or more hotends. Each extruder feeds filament to a single hotend which is used to print a section of the model. The number of extruders you’re using directly correlates with the number of different colors or materials you can use with dual extrusion being the most common setup.

   Image source: ultimaker.com

   A newer and less common technique for multi-extrusion involves one hotend and multiple extruders. Each of the extruders feeds to a coupler and only one extruder is active at a time. The active extruder continues to feed filament to the hotend. When you want to switch materials, the active extruder stops and another takes over. The residual filament in the hotend is ‘purged’ until the new material starts to flow from the hotend. This technique eliminates some of the calibration challenges associated with typical multi-extrusion and is the process used for the multi-extrusion upgrade on the Prusa Mk II.

   Prusa MK II multi-material upgrade. Image source: prusaprinters.org

   One of the bigger benefits of dual-extrusion beyond printing in multiple colors, is the ability to print your object and supports separately. This allows you to use materials like PVA filament for support structures which dissolves in water. After printing, your part can be submerged in water (or a different solvent like limonene depending on your material) to fully dissolve the supports.

    

   Filament Splicing

   Filament splicing is a technique that allows you to produce selectively colored prints with a single extruder and hotend. The Palette is one of the more popular devices for splicing filament. It takes in up to 4 different colors and ‘splices’ them together into a single continuous strand.

   The Palette filament splicing system. Image source: mosaicmanufacturing.com

   This is similar to filament swapping and dyeing, but the palette is autonomous meaning you can be more selective in which parts of your model are colored. By telling your 3D software which sections to color, the palette will automatically splice the different filaments into the necessary configuration. This technique is great for adding color to your prints but doesn’t work as well for dissimilar materials. Processes like printing the supports and object separately work less well on the palette both because splicing dissimilar materials is challenging and because the different materials require different print settings.

   Supported Technologies

   There are a few printing technologies that allow multi-color printing by default though these are currently enabled only in professional level machines.

   PolyJet is a process by which small droplets of photo-polymer resin are ‘jetted’ onto an object and then cured by a UV light. Some PolyJet machines can color these droplets prior to deposition producing a fully detailed 3D part. PolyJet machines can also print in multiple materials with one of the more common examples being the use of a wax-like material for support structures which is melted out via a heated chamber after printing.

   Multi-color print using PolyJet Technology. Image source: stratasys.com

   Binder jetting is a process by which a binder is deposited onto a powderized substrate. In this case, the binder is colored prior to being deposited. Binder jetting will often produce less crisp results than PolyJet. The colored binder can bleed into different sections of the powder leading to a more diffused color. Both PolyJet and binder jetting are industrial level processes that aren’t yet accessible to consumers.

   New techniques for printing in multiple materials or adding color to your designs are always being developed. These are some of the most popular techniques currently and offer a diverse range of costs and required equipment. If you’re more interested in painting your parts to get multi-colors, stay tuned for our blog on how to get amazing results with spray painting!