PolyJet 3D printing

PolyJet 3D printing is a 3D printing process from the material jetting family, developed by Objet, which is now part of Stratasys. Printheads similar to those in inkjet printers deposit tiny droplets of liquid photopolymer onto the build tray, and UV lamps cure them immediately. The part is built up in very thin layers, typically 0.014 to 0.03 mm.

Its main advantage is printing several materials at once. The printer combines rigid and rubber-like photopolymers and, by mixing them, creates so-called digital materials with a hardness from roughly Shore A 30 to 95. Transparent materials are also available, and color machines offer full-color printing with textures. A single print can thus contain a rigid body with a soft grip, a clear window and colored labels. Overhangs are held up by a gel-like support material that is removed with pressurized water or dissolved in a bath.

The surface is smooth and the detail very fine. Accuracy is typically on the order of ±0.1 mm for smaller parts and up to about ±0.2 mm for large ones. Surfaces that touched the support material come out matte, while the others can be glossy. The materials, however, are photopolymers with limited toughness and low heat resistance (the heat deflection temperature, HDT, of common rigid materials is only around 45 to 50 °C, although special grades withstand more), and over time they become brittle and change color when exposed to light.

Compared with SLA 3D printing, PolyJet offers similar surface quality plus the combination of materials and colors in a single part. SLA has a wider range of engineering resins and tends to be cheaper. PolyJet printers and materials are expensive, so the technology is used mainly for models and prototypes rather than end-use parts.

Choose PolyJet for visual prototypes and presentation models where look and feel matter: consumer electronics models, remote controls with soft buttons, handles with a rubber grip, prototypes of seals and membranes, or parts that simulate two-shot injection molding. It also suits transparent parts, full-color models, anatomical models for surgical planning and fine master patterns for silicone molds and vacuum casting.

In product development, it is most useful at the stage where design, ergonomics and user perception are being validated and a finished product made of several materials has to be replicated as faithfully as possible.

Do not use PolyJet for mechanical or long-term tests. The flexible materials mimic the hardness of rubber, but not its tensile strength, its tear resistance or its recovery after prolonged compression. Thin flexible walls tear easily, and rigid snap fits crack after repeated flexing. For functional testing, choose SLS, MJF, CNC machining or vacuum casting instead.

Store parts out of direct sunlight and expect them to yellow and become brittle over time. For color models, specify the required shades in your request for quote (for example to RAL or Pantone), and if the exact shade matters, ask for a sample first. Also mark the cosmetic surfaces that should be glossy, because part orientation and supports decide where the surface will be matte.