PolyJet vs. Multijet: Differences and Comparisons
Learn about the differences between these two 3D printing technologies.
PolyJet printing and Multijet printing (MJP) are both forms of additive manufacturing (AM) that build parts through the deposition and curing of UV-reactive photopolymers. In both methods, one printing head deposits the support material, while one or more other print heads deposit photopolymer droplets to build the actual part. While these two processes are similar, there are three main differences between PolyJet vs. Multijet: the materials used for printing, the build process, and the post-processing methods. Polyjet's multiple print heads allow the use of multiple materials in a single job, while Multijet's two heads restrict it to one material per part.
Both technologies use photopolymers. But, aside from the rigid and rubber-like photopolymers, PolyJet also uses “digital materials,” which are materials composed of multiple PolyJet photopolymers. The support material must be removed after the print deposition step for both methods. In the Polyjet process, it is removed using a water jet and a chemical dip. In contrast, the support material is melted away from the final part in the Multijet process.
While both PolyJet and MJP systems can be expensive, they can both simplify rapid prototyping and handle small to medium production runs. In this article, we dive deeper into the comparisons between PolyJet and Multijet and the differences between them, to help you understand which system is best for your project.
PolyJet Introduction and Comparison to Multijet
PolyJet printing was developed in 2000 by Objet Geometries. The technology was acquired by Stratasys, which has since owned PolyJet’s trademark rights. Polyjet works based on the same general concept as an inkjet printer. It deposits tiny droplets of photopolymers in pre-programmed locations to form successive 2D layers of the planned part. A UV light then solidifies the droplets to set the shape of each layer. PolyJet can deposit layers as thin as 16 micrometers, depending on the model of printer, part geometry, and materials used.
No matter how accurately it is deposited, the photopolymer deposited to form the actual part is not dimensionally stable until it is cured. To enhance dimensional accuracy and provide a frame for the photopolymer to stick to until it is cured, support materials are laid down at the same time as the main polymer part. These materials are completely eliminated from the final part. Two types of support materials are used with the Polyjet process: matte and glossy. Matte-finish supports encapsulate the entire part and help ensure dimensional accuracy. Glossy supports are used where overhangs and other complex geometry are present. Completed parts are finished by washing them with a water jet and soaking them in a chemical bath to remove the support materials.
PolyJet can be considered a similar process to multijet. One difference is that PolyJet can print parts composed of several different materials in one job. The build process and post-processing methods also differ.
To learn more, see our article on What is Polyjet.
Pros and Cons of PolyJet Compared to Multijet
Listed below are the advantages of PolyJet vs. Multijet:
- Parts composed of several different materials can be printed in one job using PolyJet.
- PolyJet-printed parts can maintain their material properties after post-processing.
Listed below are the disadvantages of PolyJet with respect to Multijet:
- PolyJet has reduced surface quality in areas where support material is used.
- PolyJet-printed parts have inaccurate printing at sharp edges leading to these edges becoming rounded.
Multijet Introduction and Comparison to PolyJet
Multijet printing is a proprietary form of 3D printing created by the company 3D Systems. MJP works like an inkjet printer. The printing head creates successive layers of the part by dispensing droplets of either UV-curable photopolymers or casting waxes. Multijet can achieve resolutions and layer thicknesses similar to those of Polyjet printing - as small as 16 micrometers. Unlike the PolyJet process, however, the MJP technology cannot print multiple materials simultaneously.
Support structures for Multijet-printed parts are composed of paraffin wax. When parts are completed, they are placed in an oven to melt the wax away. This makes post-processing much easier compared to PolyJet.
To learn more, see our article on What is Multijet.
Pros and Cons of Multijet Compared to PolyJet
An advantage of Multijet over PolyJet is in its post-processing. Multijet effortlessly completes post-processing by placing completed parts in an oven for support material to melt away.
Listed below are the disadvantages of Multijet compared to PolyJet:
- Limitations in the aesthetics of parts exist in Multijet-printed parts due to single-color and single-material print jobs.
- Multijet-printed parts tend to have altered material properties as a result of post-processing.
| Attribute | PolyJet | Multijet |
|---|---|---|
Attribute Uses photopolymer | PolyJet Yes | Multijet Yes |
Attribute Prints composite material parts | PolyJet Yes | Multijet No |
Attribute Easy postprocessing | PolyJet No | Multijet Yes |
Attribute Used for functional prototypes | PolyJet Yes | Multijet Yes |
Attribute Used for small-to-medium production volumes | PolyJet No | Multijet Yes |
Attribute Need for support materials | PolyJet Yes | Multijet Yes |
Attribute Can form complex and detailed geometries | PolyJet Yes | Multijet Yes |
Attribute Costly | PolyJet Yes | Multijet Yes |
Table. PolyJet vs. Multijet Comparison
Comparisons of PolyJet and Multijet on Key Dimensions
Technology comparison: PolyJet and Multijet systems use similar technologies and processes. Both use UV-sensitive photopolymers and a UV curing system. While not significantly different, the two methods differ in the number of print heads present in the system. PolyJet can have two or more heads, while Multijet can have a maximum of two.
Material comparison: In PolyJet systems, multiple materials can be combined into a single raw material with characteristics from all its constituent materials. These composite materials are called “digital materials.” They enable the printing of a single part with different material properties in one build.
Materials used in Multijet systems are photopolymers. Multijet-printed parts are necessarily a single color and are composed of a single material. If composite materials are needed, whether for aesthetics or functional reasons, PolyJet may be the better option.
Product applications comparison: PolyJet and Multijet both produce exceptionally detailed and functional prototypes and parts. This level of detail makes PolyJet and Multijet ideal at every step of the design process. PolyJet and Multijet-printed parts are commonly found in the dental and medical industries where they are used to create dental molds for crowns and braces.
Print volume comparison: Print volumes of PolyJet vs. Multijet don’t differ much. Depending on the system used, PolyJet can have volumes up to 260 x 200 x 200 mm and Multijet systems can have volumes up to 294 x 211 x 144 mm. If larger parts are needed, parts can be printed in pieces and then assembled afterward.
Surface finish comparison: Surface finishes of PolyJet vs. Multijet-printed parts don’t significantly differ. Because of the precise resolutions and layer thicknesses of both PolyJet and Multijet, surfaces on completed parts are smooth. Occasionally, rough surfaces may be present in more complex geometric areas but can easily be smoothed out with an appropriate post-process.
Cost comparison: PolyJet and Multijet systems can be expensive compared to other forms of 3D printing. PolyJet printers start as low as $6,000 and go as high as $75,000 for more advanced systems. Multijet printers are similarly priced and average around $43,000. MFJ parts on the whole tend to be a bit cheaper if you purchase them from services like Xometry.
Alternatives to PolyJet and Multijet
An alternative to both PolyJet and Multijet is DLP. Digital light processing (DLP) also uses cured liquid photopolymers to build parts. Curing is completed by a projector in DLP. The primary difference between DLP and PolyJet / Multijet is that parts are printed upside down, and the liquid photopolymer is deposited from a tank underneath the build platform. Despite these differences, DLP rivals PolyJet and Multijet in terms of resolution, precision, and cost-effectiveness.
Some Similarities Between PolyJet and Multijet
Similarities between PolyJet and Multijet include:
- Both use liquid photopolymers cured by UV lamps to build parts.
- Both can be used for proof-of-concept and functional prototypes.
- Both can print complex geometries that otherwise would not be manufacturable using traditional methods.
Summary
This article summarized the differences between PolyJet and Multijet 3D printing technologies.
To learn more about PolyJet vs. Multijet and to help select the perfect technology for your products, contact a Xometry representative.
Xometry offers a full range of 3D printing services for your project needs. Visit our Instant Quote Engine to get a free, no-obligation quote in minutes.
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