Additively produced parts can be colored in two different ways. They can either be colored later in post-processing - or they can be produced directly with colored printing material. Both methods have their advantages and disadvantages. And the same applies to both: colorful 3D parts are much more interesting and often more useful than the standard materials in gray or white. You should not shy away from the costs if color is to come into play. This only increases production costs by 10 to 15 percent.

Direct or indirect printing?

If you want to print in color, you have two options: Direct or indirect 3D color printing. With the direct method, a colored filament is used to produce the models in 3D. The most popular technology for colored filaments is Fused Deposition Modeling (FDM). It is one of the most widely used additive production processes on the market. FDM parts are available in a wide range of colors (black, blue, grey, ivory, red) and also in the most common materials such as ABS and ASA.

However, when 3D printing multi-colored parts with FDM, a single material must be used for the entire part. It is therefore not possible to switch from white ASA to black ABS, for example. In principle, all common materials such as ASA, PLA and ABS are available in a wide range of colors. If you want a multi-colored part, you split the CAD model into the different colored components and assemble the individual parts later. This technology makes it possible to achieve vibrant colors and beautiful details.

However, monotone colors are not as precise as in MJF printing. Another disadvantage is that the colors cannot be mixed in FDM printing. This means that not all RAL colors can be selected with standard solutions. To avoid the disadvantages of FDM printing, indirect color printing is an option. Here, the color is applied from an external source during the printing process, as is the case with MJF technology (Multi Jet Fusion). This is much more precise and therefore enables a more realistic appearance of the 3D parts. Indirect 3D color printing uses the CMYK color mode, which must be taken into account when preparing the workpiece.

Multi-Jet Fusion is also the only technology that can print technical plastics (polyamide, nylon 12) in full color. This makes it possible to produce functional parts with optimum mechanical properties. As this is indirect 3D printing, the technology is able to produce full-color parts with very accurate color reproduction using a voxel control system.

Due to its good mechanical properties, MJF can also be used for end-use parts. The process is also very cost-efficient, especially for small and medium-sized series. It is also suitable for series production due to its high productivity. On the negative side, the method does not offer color transparency. Even small and very sensitive parts should not be produced in color in this way.

The production platform Xometry has gained a lot of experience with color 3D printing. Industrial and private users alike can place orders on the website, which are executed in a huge network of suppliers. As is usual with digital platforms, a CAD model of the part is uploaded in advance. However, not all file formats contain information on the desired colors. This applies, for example, to the .stl or .catpart formats. If you want to print a model in color, you should therefore create an additional .obj file with information on the color texture, especially for MJF.

Post-processing - the color comes later

If a filament or powder is not available in a desired color or the technology does not offer a colored printing material, the post-processing option makes sense. Various options are also available here:

Spray painting
Here the paint is sprayed onto the 3D part. This is a simple and therefore very common coloring technique. It is also used for conventionally manufactured parts. The major disadvantage is that the paint only lasts on the surface level. Because it does not penetrate deeper into the material, it is sensitive to scratches and wear. In these cases, the natural color of the part becomes visible again. Spray painting in 3D printing can be used in the following processes: MJF, SLS, SLA, FDM.

Coloring
Here, the plastic is deeply colored. This produces particularly vibrant colors that are also resistant to peeling or scratching. Because no thick layer of color is applied, there is also no loss of detail. A part colored in this way therefore corresponds most closely to the original design. This is particularly important if the 3D printing process was chosen due to the complexity of the design. Many users prefer their product to be completely in uniform black because this gives them a coherent overall look. The coloring method is possible with MJF and SLS.

Dmitry Kafidov, Managing Director Xometry Europe