3D Printing News

This month: Printing in full-colour 3D using ColorJet

In this first of several monthly features on 3D printing by Toronto’s Objex Unlimited 3D Print Studio, Brand Manager and Marketing Coordinator Matt Belo explores the fascinating world of 3D ColorJet Printing.

ColorJet printing

ColorJet Printing (CJP) is an additive manufacturing process used to create full-colour, photo-realistic 3D models. The range of applications includes concept models, marketing materials, natural models (including humans, animals, geographic/nature images, 3D selfies, etc.), artistic projects and architectural designs, to name a few.

Colour printing versus full-colour CJP

Many traditional colour 3D Printers operate using multiple print cartridges, each containing a single-colour material. With these printers, the number of cartridges your printer can utilize limits the number of colours in your print. In other words, if you have five colour cartridges, your model can contain only five different colours. With ColorJet printing, because the colours are mixed in the printer, you can get very complex colouring – including gradients, textures, patterns and skin tones. The additional benefit is you can apply a ‘texture-map’ to your print, as opposed to breaking your design file into multiple sections and colouring each one manually. This is the only method to get photorealistic coloured models.

The CJP process

The ColorJet Printing process involves two primary components: Core and Binder material. The core material can either be a gypsum-based or plastic-based powder. For the first layer, the print bed starts at the highest position in the printer. A roller is used to spread a very thin layer of core powder across the print bed. Once there is a thin layer powder across the print bed, the printer selectively jets coloured binder material in specific areas where the 3D model is being built to solidify the core material. The different coloured binder materials are mixed together to produce millions of colours – in the same way a 2D Printer combines ink. Once the binder is applied, the process repeats, spreading across a new layer of core material and using binder to attach that material to the layer below. After several thousand layers (depending on the size of the model), the end result is a full-colour, three-dimensional model.

The finishing process

Due to the nature of the colour printing process, when your print is done you’ll have to extract the finished part from a bed of unused core material powder. The benefit of this is that the models are self-supporting – the unused core material remains in the print bed supporting any overhangs within your print, eliminating the need for any support material. In their unfinished state, the models are extremely fragile, therefore you must extract the part from the powder very carefully. Once you have extracted your part, you use air to blow away excess core material (which gets recycled back into the machine), sand your part to get a smooth finish, and then dip it in cyanoacrylate (superglue) to make it stronger.

File preparation

Your file needs to follow the general rules of a “print-ready” 3D file. This means it needs to be completely closed (or watertight) and each of its edges needs to be shared with two polygons. Additionally, with ColorJet printing, it needs to be a certain thickness so that the model can actually support itself in the printer. To save on material costs, ColorJet models are generally hollowed. Most 3D printers use “.stl” files, but with CJP, you need to provide a colour 3D file – generally a .zpr or .wrl file. Anything else must be converted and sent along with a texture map file (usually .jpeg or other 2D formats) which contains all the complex colour data that will be applied to the 3D model. There is a bit of a learning curve to preparing these files, so I recommended you contact a ColorJet Printer operator to give you advice on preparing your files. Objex Unlimited is happy to share this type of information.

ProJet 660Pro

While there is a range of 3D printers in the ColorJet Printer line, the 660Pro is one of the printers that includes many key features – full CMYK colour, attached model finishing chamber, a faster-than-average print speed, and a larger-sized print bed. It’s also quite affordable when compared to other professional-level 3D printers. However, there is a full range of ColorJet Printers that make up the ProJet x60 series, from the more budget-friendly ProJet 260C, to the large-build area of the ProJet 860Pro.

If you have any further questions on anything 3D-related, please don’t hesitate to contact us at www.objexunlimited.com. Or visit our Objex Unlimited Studio at 36 Fieldway Road in Toronto.

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