Polyjet & Multijet Modeling (MJM)
Polyjet is an amazing rapid prototyping technology. Polyjet combines high accuracy (down to 16 µm layer height and tight tolerances) with the possibility to combine more than one material in the same print. Furthermore, it is possible to dynamically mix materials and create “digital materials” with new characteristics. For example, it is possible to print rubber like materials targeting a specific Shore A hardness.
Another key feature of Polyjet is the ability to print with transparent resin (called VeroClear). A popular use case is to print distinct white or black structures within a transparent shell – a useful way to visualize complex biologic structures or the inner workings of complex prototypes.
In Polyjet 3D printing a print head is suspended above a build platform. The print head contains several nozzles, as well as a UV lamp. During printing, the print head will sweep over the platform, ejecting tiny drops of a light-curing polymer on to the printing platform, then almost immediately curing it with UV light. The platform then lowers between 16-32 microns (depending on the machine and setting) and the next layer of polymer is applied to the already hardened previous layer. This process continues until the object is completely 3D-printed. Overhanging sections are stabilized during the print by waxy support material, which needs to be manually removed after the print is completed.
Illustration of the Multijet Modeling Process by 3D-Systems. Polyjet is a very similar technology. Reference: Youtube/3D-Systems
High-resolution, high-accuracy prototypes can be created with Polyjet or Multijet Modeling. The advantages are:
- High accuracy: most of the models can be built with < 0.1 mm of tolerance. The technology is less prone to shrinkage or warping than other additive technologies.
- High surface quality:
- The layer-height is very low (~16 – 32 µm), therefore in z-direction the surface is better than most other 3D printing technologies
- However, unlike other 3D printing technologies, layer lines can be also seen in X-Y-direction.
- Rigid materials can be sanded or bead blasted to create very smooth surfaces
- High resolution: the droplets are very fine and can create small features.
Prototypes for investment casting
For investment casting, Polyjet and stereolithography are the most commonly used additive technologies. Polyjet has advantages over Stereolithography for smaller parts with small details or parts with undercuts, since the support material can be easier removed.
Two materials can be printed in the same object. Typical combinations are
- Transparent (VeroClear) / Non-Transparent (e.g. VeroWhite or VeroBlack): Used to display interior structures of an object (e.g. channels or biological structures)
- Rigid (Vero) / Soft (Tango): Often used to create life hinges, over-molding simulations or include sealings in an object.
- Very high accuracy and resolution
- Very smooth surface; fine layer lines can be easily removed
- Can combine different materials
- Support material creates alterations in surface quality (no support: glossy, smooth; with support: dull, rougher)
- Relatively high cost compared to other 3D printing technologies
- In Polyjet, sharp edges are often slightly rounded
There are plenty of materials available for this technology. We offer 4 standard materials. Besides the ‘pure’ materials, it is possible to ‘blend’ materials during the print process. As an example, Tango with a shore hardness of around A25 can be mixed during the print process with traces of Vero, to create a digital material with a final shore hardness of A 50 or higher. Based on this method, soft materials can be created with a shore hardness range from ~A25 – 95.
This rigid material simulates the mechanical and thermal properties of ABS. Unlike FDM printed (extruded) ABS, significantly higher resolutions can be achieved.
This flexible material (Rigur) simulates the mechanical properties of Polypropylene. It can be used for snap fittings and other applications, where flexibility is required.
Rigid Polyjet materials can be well processed after printing. Unfortunately, soft materials can not be post-processed (except support removal). Our finishing options for rigid materials include:
- Removal of support structures (standard)
- Glas bead blasting (on request, free of charge)
- Spray painting (on request with additional fee)
- Coating (on request with additional fee)
The Polyjet (a.k.a. Multijet Modeling) technique was developed by the company Objet Geometries Ltd.. Objet was founded in 1998 by Rami Bonen, Gershon Miller and Hanan Gotaiit. After about ten years, the company presented the first multi-material 3D printer. In 2012, the first 3D printer with more than 100 combined materials was introduced by Objet Ltd. In the same year, Objet merged with the industry giant Stratasys.
Over the history of Objet Ltd. a total of 50 patents were registered. Among which included the first printer (their “Rapid Prototyping Apparatus”) as well as a method and an appliance for curing of waste-containing photopolymer components. Both patents were registered in 2009.
The patents and printer were taken over by Stratasys after the merger and further developed. Stratasys maintains the Objet brand in the market, using it for printers in the Design Series and Dental Series.
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