3D printing · process family

PolyJet / MJ

Material jetting · MJ · PolyJet · NPJ · DOD

Inkjet droplets of resin, cured on the fly by UV

Think of a 2D inkjet printer turned into 3D: hundreds of nozzles jet tiny droplets of photopolymer across the build area and a UV lamp cures them instantly, layer by layer. Because different nozzles can jet different resins in the same pass, material jetting is the way to print full colour and multiple materials — rigid and rubbery — in a single part, with a very smooth surface.

jet · UV-cure
PolyJet / MJ — inkjet droplets of resin, cured on the fly by uv.
0.014–0.03 mm layers
Resolution
Moderate
Speed
$$$$
Cost
Good
Isotropy

How it works

  1. 1
    Print heads sweep the build area, jetting droplets of photopolymer where the layer is solid.
  2. 2
    A UV lamp on the carriage cures each pass almost immediately.
  3. 3
    A separate, dissolvable or gel support material is jetted under overhangs.
  4. 4
    The platform steps down and the next layer is jetted and cured.
  5. 5
    Supports are washed or melted away to reveal a smooth, full-colour part.

The machines

The variants of this family, from the hobby basics to the industrial state of the art.

PolyJet (Stratasys)

Industrial

Jets multiple photopolymers plus support; blends 'digital materials' and full colour in one build.

Material Jetting (3D Systems MJP)

Industrial

Jets a UV resin with a meltable wax support — high accuracy for casting patterns and fine models.

NanoParticle Jetting (NPJ)

Industrial (metal/ceramic)

Jets a liquid carrying metal or ceramic nanoparticles; the carrier evaporates and the part is sintered — jetting extended to metal/ceramic.

Strengths & limits

Strengths
  • Full colour and multiple materials in one part
  • Very smooth surface, high dimensional accuracy
  • Rigid-to-rubber gradients ('digital materials')
  • Fine features and thin walls
Limits
  • Expensive machines and materials
  • Photopolymers are brittle and UV-/heat-sensitive
  • Support removal needed on nearly every part
  • Parts age and can warp over time

Typical parts & materials

Feedstock: Liquid photopolymer (or nanoparticle ink) · Thermosets (photopolymers); metal/ceramic via NPJ.

Typical parts: Realistic full-colour prototypes, medical and anatomical models, over-moulding mock-ups, investment-casting patterns

Commonly run in — open one for its cited properties:

Photopolymer (rigid)Rubber-like photopolymerDigital / blended materials

What's new

Full-colour, multi-material realism keeps improving (thousands of colours, tunable transparency and shore hardness), and jetting has been pushed beyond polymers into metal and ceramic via nanoparticle inks.

Part of the 3D printing guide. Compare the other process families, see the design rules, or browse the cited materials database.