3D Printing in Full Color

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One of the more exciting trends in 3D printing has been the move towards full color printing. Not only confined to using 3D printing to be able to evaluate complex geometries, we can now print in full color for a much better ability to experience a prototype that is much closer to the final product than ever before. Artists and designers alike can harness this technology to accurately apply colors and textures in ways that before were either laboriously done by hand or simply impossible. One printer technology has this ability is Stratasys’s PolyJet technology. Combined with one of their newest PolyJet printers, the J750 or the even newer J735, and its ability to mix up to 6 different materials simultaneously, allows for ~360,000 different color combinations.

PolyJet technology works very similarly to inkjet printers; you may be familiar with inkjet from your home or office. A print head jets very fine particles of ink onto the paper in sequence in order to create the words/images on the document you sent to be printed. PolyJet is very similar, but instead of ink it uses a UV cured polymer to build each layer. This allows for very fine details and mixing of materials. PolyJet can print in full color, clear parts, flexible and rubber like materials.

In order to utilize the full power of PolyJet, special consideration must be taken during the post design file preparation stage to ensure prints are able to be constructed as desired. If you simply want to print multiple bodies of different colors (i.e. a red ball, blue cube, and yellow pyramid) this is accomplished very easily in GrabCAD print by selecting the material per body. However, when you need multiple materials within the same print (i.e. printing a full color planet model of earth), extra considerations must be made.

There are two ways to go about multi-material prints on the J750. The first is by using multibody STL files. This allows for limited control of surface color. Think of a polka dot pattern; multiple colors, but as distinct bodies. The multi-material part must be designed as an assembly or multibody part within your 3D CAD software. Once each color is its own body, you can export the entire assembly as a multibody STL file, which will actually create several new STL files offset from their common origin in their correct assembly positions. Once you have imported these files to GrabCAD print, you can then select each body’s specific color/material property characteristics.

What if you need something more like a wood grain texture though? Splitting a model into enough distinct bodies to get a good looking texture would be impossible as the number of bodies needed would be massive. So there is a much better way, through use of VRML files. VRML files are similar to STL’s or STEP files in that they contain geometry data, but they also carry color and texture data. This allows the color choosing phase of the print to be completed entirely by the designer ensuring they get exactly what they need out of the printer. Designers must simply apply their desired color scheme to their part once they are done designing and ready to print. From there, it is a very simple File->Save As->.wrl filetype and then the design can be loaded into GrabCAD print and printed with very minimal user interaction. This is the most powerful workflow used to create multicolor prints on the J750 and should always be used when the J750’s full 360,000 color palette abilities are required.

 

Cullen Williams
Additive Manufacturing Application Engineer
Computer Aided Technology, LLC