Multi Jet & Poly Jet Fusion (3D Printing)

 1. Multi Jet Fusion 3D printing

HP's multi-jet fusion printing method is an example of a cyber-physical system founded and developed by Hewlett and Packard (HP). This method works by the 3D modeling which is software-based and following the CAD design, the printing operation of objects is carried out.   Materials like PolyAmide12 (PA12), PolyAmide11(PA11), and Glass beads are mainly used for object printing and coating. 

 

Figure 1. Schematic representation of Multi Jet Fusion working principle [Source: https://iopscience.iop.org/article/10.1088/1361-665X/ab0dd6] 

The material coating powder is first sprayed on the fusion bed as illustrated in Figure 1. In the following stage, the fusing agents are applied to the areas where material fusion is required. These fusing agents are responsible for the precise forming of the shape of the object. Subsequently, detailing agents are applied to the unfused powder around the fused object. This stage can give a detailed and finished look on the outer periphery of the object required. Energy in the form of heat is supplied in the next stage to bind the coating powder uniformly with the fusing agents and in the final stage, fused object and unfused powder are left for further processing following the same steps respectively in a layer-by-layer approach as processed by the 3D modeling and slicing software. Extra fusing agents and powdered materials are extracted to the Extraction tank and the printed object undergoes cooling processes. This MultiJet 3D printing method developed by HP shows a dimensional tolerance of ±0.1%. 

  

2. Poly jet 3D printing

The Poly jet printing system was founded by Objet Geometries Ltd. in 2000. It functions on the basic working principle of inkjet printing similar to the HP MultiJet printer. Poly jet printing is done by using the photopolymerization process. This printing method works in three steps; pre-processing, processing and post-processing. It can be further demonstrated using a visual representation of the setup. 

Figure 2. Schematic representation of Poly jet printing process [Source: https://doi.org/10.1051/matecconf/201711203011] 

In the pre-processing, the object to be printed is mapped out by the 3D CAD software and the object design is sliced down into layers. The pre-processing stage plans out the movement of jets to print the object. In the subsequent stage of processing, resin drops are applied layer-by-layer conveying the printing process forward and the fusing temperature of the material is achieved with the heat applied by the U.V. lamp. Particles of material (Resin) are fused together uniformly and this process of fusion is called Photopolymerization. Two different materials are used for this technique; model material and support material. Support material creates a platform structure for the model material and also acts as the reference photopolymer for printing. After the printing of all the layers is executed with the moving of the build platform as required, post-processing is done with water jets at the recycling station. In this stage, the surface of the object which is printed gets a detailed finish and the support material is also ejected from the main model structure. Hence, this technique can be used effectively to fabricate thin walls, complex geometry, smooth and aesthetically detailed designs with a dimensional tolerance of ±0.1%. 

A visual representation of typical Multijet and Poly jet 3D printers available commercially are illustrated below:

HP 3D Jetfusion 4200 (Multijet 3D printer)

Stratasys Objet printers