Multi-colored prints can be achieved with a single extruder by assigning multiple tasks within your slicing software. The resulting G-Code will instruct your printer to begin with a single color filament and then pause at a certain layer height. At that point, a new filament is swapped out and the print job is resumed. This technique allows anyone with a standard single extruder printer to create a multicolor object.
If swapping out filament during a print job sounds tedious, then take a look at Mosiac Manufacturing’s Palette+. It is designed to allow a single extruder 3D printer to easily print up to four different filaments at the same time. Taking four separate filaments as input, it fuses them into a single multicolored filament strand. Because the fusing process is controlled by the slicing software, a model has the exact amount of color required for a specific area of a 3D print.
Dual extrusion printers are fairly common now, frequently used to combine normal filaments with soluable support materials. Complex models can also be printed in two solid colors using two different filaments that are desposited within a single printing session. The Original Prusa i3, with its MK2/S Multi Material Upgrade Kit ups the ante with four extruders depositing four different filaments within a single printing session.
There are advantages and disadvantages to these methods of direct color 3D printing. The main advantage is that it is easy to achieve large areas of saturated color.
The main disadvantage is that mixing colors is impossible and, as a result, photo-realistic textures are impossible to reproduce. Additionally, using a printer with multiple extruders expands the possibility of potential errors since each extruder might jam or produce layers of varying quality. Finally, prints are only as good as the filaments used. Filaments from different manufacturers might lead to jams or bonding issues between layers of different filament colors.
3D color prints that require subtle color changes are best achieved using indirect color printing processes. Here, color is applied from an external source to the filament during the printing process. While these processes have previously been the domain of high-end 3D color printer models and online services, the technology is now filtering down to consumer 3D printers.
Many companies offer high-end 3D printers that produce full-color prints. However, the price for these printers is well above the budget of the average consumer. These machines are industrial 3D printers that produce color prints in a variety of materials.
Stratasys has long been a leader in high-end 3D color printing, offering a number of different printers at various price points. The company’s PolyJet printer builds models by depositing layers of liquid photopolymer as thin as 16 microns (0.0006”) and simultaneously curing it with UV light.
HP’s Jet Fusion 3D Printer promises to create 3D prints in full color in the same amount of time that competing products can create a single print. HP’s proprietary process uses CMYK (cyan, magenta, yellow and black) pigments that are mixed at the “voxel” level — a.k.a. the tiny three-dimensional pixels that form the DNA of Multi Jet Fusion. This process gives HP’s color 3D printer its unique ability to print objects with incredibly precise color, shape and detail.
Other companies offer their own high-end 3D color printers, such as the 3DPandoras 1.0, which uses gypsum powder, a clear binder, a curing agent and CMYK inks to produce beautiful full-color prints.
Mimaki is another company showing off their own high-end full color 3D printer. Their printer uses a UV curing technology originally developed for 2D printing. A pigmented UV-curable resin is jetted through industrial inkjet heads, which is then cured into a solid state.
One of the largest advantages that the company brings to the space is variety. Unlike Stratasys’ J750, which boasts 360,000 colors and six different textures, the 3DUJ-553 can produce over 10 million colors.
If high-end machines are beyond your reach, then 3D printing online services provide a wide range of options to anyone looking to get professional looking 3D prints. Many services provide the option of printing in various materials as well as printing in millions of colors. Websites like Shapeways, Sculpteo and i.Materialize are a good place to start when investigating the wealth of options available. In order to get a full-color print, upload the model, pay the appropriate fee and within days your full-color 3D model will be sent back to you.
Up until recently, the only types of materials provided by 3D printing services used plaster or sandstone as based materials. These materials produce great results but are fragile. Companies like i.Materialize now provide full-color printing with plastic using the CMYK inkjet process similar to a standard inkjet printer used to produce colored images on paper. The main advantage of plastic is that it is more robust and less likely to break or shatter when dropped.
MCor has been creating full color 3D printer models for many years, but with a twist. Instead of plastic, their printers, such as the ARKe, use regular printing paper. The use of paper allows MCor’s printers to deposit standard CMYK inks on each sheet of paper in millions of color combinations before the layer is die-cut and fused with the next layer of paper. The result is a full-color print. The main problem with this technique is that the inks can bleed or spread, resulting in “soft” details. Still, the results remain impressive.
XYZPrinting has expanded its range of consumer FDM printers with a full-color 3D printer called the Da Vinci Color. Using a similar CMYK process to the MCor printers, this printer deposits a specially-formulated filament that can absorb CMYK inkjet inks before the next layer is applied, resulting in an impressive full-color print. As with MCor, the final print exhibits “soft” details because the ink can seeps into the filament, resulting in areas where one color bleeds into another. Additionally, the surface of the print has a slight translucent appearance as if the color is trapped inside rather than being on the surface.
A major drawback of these types of CMYK-based 3D printing is the integrity of the 3D printed surface. Any irregularities that might occur during the printing process are difficult to fix because the color is fused into the filament. Sanding down or repairing a 3D print that is already full-color causes blemishes on the surface, which mar the final appearance.
The common element to both high-end and consumer-level full-color 3D printing is the use of ink-jet technology to generate the millions of colors that CMYK printing allows. Unforunately, the results can be unpredictable. The problem isn’t with the technology, it lies in how a particular color is described. Texture maps used to create 3D graphics are often saved in RGB (Red, Green, Blue) format, which create vibrant colors on screen but do not always translate correctly into the CMYK color process.
RGB is considered an additive color format. If you were to combine all three RGB colors at full strength, the result would be white. CMYK is considered to be a subtractive color format. Mixing all four CMYK colors at full strength produces a muddy black, and you can’t generat white using CMYK inks. (White is the uncolored surface that the CMYK inks are printed onto.) Thus, in the case of 3D color printing, white filament is required for CMYK inks.
To get the best results from CMYK inkjet technology, some understanding of CMYK color correction is required. Imagine you want to make a 3D print of a green Christmas tree that uses a texture map for all the color information. If the texture map was created in RGB format, the color will look vibrant on your computer screen but might appear dull when 3D printed. Examining the color channels in a program like Photoshop will reveal that a lot of cyan and yellow ink is being used (which is appropriate to create green) but might also reveal that magenta and black inks are being used as well, which will dull the color. These “contaminating colors” are unnecessary to produce green, while boosting the cyan and yellow inks in their respective channels will yield a much more vibrant green color when the 3D print is produced.
The desciption of this process is greatly simplified here but the results are worth the effort. There are many YouTube videos that describe color theory and the differences between RGB and CMYK color. A good basic description can be found here: https://youtu.be/YtH9eXWuf3Y.
Whether you generate color using multiple filaments or use some sort of CMYK process, the future of full-color 3D printing appears bright. Those of us old enough to remember the advent of inkjet printing will remember that the first printers didn’t always produce vibrant results. As the years went by, the process required to generate fantastic color prints at home improved to the point where professional results can be achieved with even the cheapest of printers. We are in the early stages of full-color 3D printing. As the technologies improve, so will the results. In the years to come, we will all be able to print full-color 3D prints as easily as we can print our favorite photos on paper.
License: The text of "Color 3D Printing – How To Get Colorful 3D Prints" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.
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