PolyJet 3D Printing is similar to ink-jet. But instead of injecting drops of ink on paper, 3D printers inject liquid curable photopolymer layers on a build tray.
The 3D printer injects and instantly cures UV liquid photopolymer in tiny droplets. Thin layers accumulate on the build tray to create an accurate 3D model or prototype. When raised or complex parts require support, the 3D printer injects a gel type removable support material.
They combine several 3D printing materials into one model by simultaneously injecting many materials.
This means that for a single printed prototype, you can position multiple materials of your choice, and even combine two or three materials to create digital composite materials with different properties; combining rigid materials and rubber.