Polyjet is a proprietary technology by Stratasys. Polyjet, as the name suggests, (poly=many) consists of an array of jets(nozzles) mounted on the print-head. These jets have an aperture diameter of approx. 22–28 microns. The layer thickness in Polyjet technology goes as fine as 16µm i.e 0.016mm. Polyjet process has support structure generation. These are wax-like supports which can be easily peeled off manually or they can be removed with the help of water jet.
Polyjet technology uses photopolymer resin materials that are UV cured. The process consists of a print head that deposits the material through an array of small nozzles, adjacent to which is a UV lamp that cures the resin as it is deposited. The resin materials come in form of cartridges. The biggest Polyjet machine — Stratasys J750 is a state-of-the-art machine that can house 6 different material cartridges at a time.
Apart from the special materials, Polyjet materials are basically divided into two broad categories: Vero family and Tango family. The Vero family consists of all the rigid materials viz. Vero White, Vero Clear, Vero Magenta etc., whereas the Tango family consists of flexible materials viz. Tango Black, Tango Plus, Tango Black Plus etc.
The Stratasys J750 is capable of producing digital materials. Digital materials are those materials wherein two or more materials are mixed together to achieve a composite material having hybrid properties. Thus you can mix the materials to manufacture a part having varied shore hardness throughout the part geometry.
We tried fabricating this butterfly hinge in multi-materials(Vero+Tango). The hinge sections were fabricated in Tango material whereas the rest of the part was fabricated in Vero material.
One can select the Polyjet shore hardnesses in the following steps: 30A, 40A, 50A, 60A, 70A, 85A and 95A. The Vero materials have shore hardness in the range of 83-86D, whereas the Tango Plus material has a shore hardness of 30A. Thus, to achieve a part having shore hardness 50A, you will have to mix a Vero material with a Tango material. The printer software will automatically calculate the amount of rigid material that needs to be mixed with the flexible material to achieve the desired shore hardness.
Eg: Tango Plus has an inherent yellowish-clear tinge. If a Vero white material is mixed with a Tango Plus material, you will get a part that is flexible(depending on the amount of Vero material added) and slightly whitish-clear. The end-part color will highly depend on the type and proportion of material that is being mixed.
A major application of Polyjet lies in molds for injection molding. Polyjet molds are mounted on the injection molding machines to produce 50–100 pieces. They are used to simulate parts in end-use materials before opting for mass manufacturing.
Apart from Polyjet molds, Polyjet technology finds application in industries requiring small, precise components that won’t be subjected to severe loading conditions.