3D Printing in Colour. What you need to know.

Posted on Jul 17, 2020

Colour 3D Printing

Update - July 2020

Since our last blog post on 3d printing in colour last year, things have move on at a pace.

The majority of our colour 3d printing is via the Stratasys polyjet J750 system although we expect to supplement this with the HP Multi Jet Fusion Colour system soon. The information regarding colour flexible parts is specifically for the Stratasys J750 Polyjet system.

Before we start it might me useful to clarify some terminology with a short glossary:

Spot Colour - A single colour allocated to a design or an element of a design.

Full Colour - Photo, patterned designs printed using a mix of CMYK colours.

CMYK - Cyan, Magenta, Yellow and Black (K). The four 'process' colours used in full colour printing. Mixing tiny dots of these colours gives a wide spectrum of colour. Used in commercial paper printing.

Rigid - Parts made from the Vero family of materials based on Vero White, Cyan, Magenta, Yellow and Black. Not Flexible.

Flexible - Parts which can be made with assorted Shore A values from the Rigid Vero material PLUS the addition of the Rubber like Agilus material. It's the addition of the Flexible material which limits the pallet of available colours.

GrabCad - The software which sets up your CAD files before sending to Stratasys 3D printers. Free to download from the GrabCad web site once you register for an account. Useful for checking print files before sending.

J750 - Our go to colour 3D printer.

Assembly - A design made of of several elements, each of which can be allocated a spot colour. Sometimes provided in the form of several STLs which locate relative to each other to form a whole. It's important that they connect so that the finished print does not separate into it's constituent parts (!).

Colour 3d printing in Flexible and Rigid materials. 

A great feature of the polyjet system is the ability to 3d print both rigid and flexible parts. Both rigid and flexible can be 3d printed in colour but with some differences:

Rigid Vero parts - Spot colour or Full colour
Flexible Agilus parts - Spot colour with a reduced colour pallet. The softer the material the softer the colour:

Which File Formats for colour 3d printing ?

For Rigid spot colour or full colour designs printed in Vero materials, then a VMRL file is the best solution. Other native CAD formats can also support colour information, for example STEP and SLDPRT files. However these don't support texture information and we need to confirm if they will support 'full colour' designs. Anecdotal evidence suggests that even spot colours resolve better from a VMRL file.

For Rubber like and flexible designs, colour needs to be assigned using the colour picker in GrabCad from the available colour pallet. Available colours will depend on the Shore A value or hardness you need from the print. Colours tend to be more 'pastel' in tone due to the flexible material in the mix. A STL or STL assembly is a good solution.

Spot colours can also be applied to designs manually, for example to to a shelled STL or a STL assembly.

 

In addition to VMRL and STL formats, GrabCad, the software which drives the printers supports many other formats:

https://help.grabcad.com/article/214-list-of-supported-file-formats?locale=en

 

Matt or Gloss Finish?

The Matt setting gives the 3D print a uniform finish by coating the whole part with a layer of support material which is then removed. It is where support material comes onto contact with the model that gives the Matt surface finish.

The Gloss setting gives a shiny more vibrant finish to the TOP surfaces where support material isn't required. However it's impossible to build a model without support material, so some faces of the design, e.g. the undersides and sides, will still be Matt. A 100% gloss finish is not possible.

We generally default to Matt to give a consistent finish but are happy to print the gloss setting, orientating your design to give a gloss finish on the surfaces you require.

 

 

 

Further Reading:

The GrabCad web site has loads of tutorials:

https://grabcad.com/tutorials/polyjet-multi-color-design-guidelines-for-3d-printing

https://grabcad.com/tutorials/how-to-3d-print-in-full-color-part-2-repairing-and-checking-vrmls

Downloading the GrabCad software and setting up a J750 printer template will also allow you to quickly see how your your file outputs are resolving.