PolyJet vs. MultiJet: What’s the Difference?
Comparing these two 3D printing technologies
Both PolyJet and MultiJet (MJP) 3D printing are additive manufacturing methods that build parts by depositing and curing photopolymers that react to ultraviolet (UV) light. They can both be used for proof of concept and functional prototypes and can make complex parts, some of which are often found in the dental and medical sectors, specifically for things like molds for crowns and braces. Despite these commonalities, these two processes have some key differences that make one able to print with composite materials and the other better for small-to-medium production. Read on to find out which.
What is PolyJet Printing?
First developed in 2000 by Objet Geometries and acquired by Stratasys, who now owns its trademark rights, PolyJet printing works similarly to an inkjet printer. “PolyJet is a process by which material is jetted onto a print plate layer by layer,” says Christian Tsu-Raun, the Team Lead at Xometry’s Manual Quoting. “It’s relatively slow but very accurate, and good for small, nonfunctional prototypes.” In the process, tiny drops of photopolymers are released in areas that have been programmed beforehand to create 2D layers on top of each other. It then uses a UV light to harden those drops and set each layer’s shape.
Depending on things like the model, how complex the part is, and which materials are used, PolyJet can create layers as thin as 16 micrometers.
The photopolymer will only become dimensionally stable when it’s cured. That’s why support materials are usually laid down at the same time as the main polymer part, which enhances its dimensional accuracy and provides a sort of frame for the photopolymer to stick to until it’s cured. These support materials—which will be removed later—are either matte or glossy. Matte supports are good for dimensional accuracy, and glossy ones are used when you have overhangs or other complex parts. When the part is finished, it’s washed with a water jet and soaked in a chemical solution to remove the supports. The following is an image of a Xometry rainbow logo made with PolyJet printing:
PolyJet is a method that allows you to print using various materials in one job, and parts will usually maintain their material properties after being post-processed. The downsides to using this technique, though, are that the areas that are attached to support materials will be of inferior surface quality, and it’s not the best method for making sharp corners—they tend to get a little rounded off. We’ve written all about PolyJet 3D printing which you might find helpful if you want to learn more on the process.
What is MultiJet 3D Printing?
MultiJet’s creation is attributed to the company 3D Systems, and it’s another type of 3D printing that works kind of like an inkjet printer. Like the first method we discussed, MJP uses a printing head that creates parts layer by layer using either UV-curable photopolymer or casting wax droplets. It can also create layer thicknesses of as small as 16 micrometers, but unlike PolyJet, it can’t print multiple materials at once. Support structures for this technique are made from paraffin wax, so when a part is finished, it’s put in an oven to melt the wax away. This post-processing is much easier than PolyJet printing. We have a whole article on MJP which you can read to learn more about the topic.
The potential downsides of using an MJP machine include the fact that parts could look slightly inferior to something made using a PolyJet printer because you can only use one color and one material per job. Also, MJP parts could have their material properties changed during post-processing. The below image shows a benchy that’s been made using MJP printing:
| Attribute | PolyJet | MultiJet |
|---|---|---|
Attribute Prints composite material parts | PolyJet Yes | MultiJet No |
Attribute Used for small-to-medium production volumes | PolyJet No | MultiJet Yes |
Attribute Number of print heads | PolyJet Two or more | MultiJet Maximum of two |
Attribute Materials | PolyJet It can use several materials and blend them into a single one, called a “digital material,” which has characteristics from all of them | MultiJet Photopolymers of a single material and single color per print |
Attribute Print volume | PolyJet Usually up to 260 x 200 x 200 mm | MultiJet Can be up to 294 x 211 x 144 mm |
Attribute Surface finish | PolyJet Generally smooth | MultiJet Usually smooth |
PolyJet vs. Multijet
Frequently Asked Questions on PolyJet vs. MultiJet
How much do these machines cost?
They’re not cheap. PolyJet printers are usually between $6,000 and $75,000, and MJP machines are quite similar, averaging out at around $43,000. MJF parts tend to work out a little cheaper if you buy them from services like Xometry.
Are there any alternatives to PolyJet and MJP?
DLP (digital light processing) is a comparable 3D printing method that also makes high-resolution and precise parts cost-effectively. Like PolyJet and MJP, DLP uses liquid photopolymers that are cured layer by layer to build new parts, but it does so with a projector instead of a printhead. In addition, DLP typically prints parts upside down, and the liquid photopolymer comes from a tank underneath the build platform.
What’s the difference between PolyJet and SLA?
SLA (stereolithography) 3D printing uses a laser to cure liquid resin into solid parts. It’s good for making functional prototypes and parts, and, depending on the specific machine and setup, it could have even better resolution than PolyJet. SLS prints are high-quality and often made into molds and tooling and used for making patterns and textures on surfaces.
What’s the difference between MJP and MJF?
Both methods seem similar even by the name, with MJF being an abbreviation for multi-jet fusion. “MJF is a process by which a fusing agent is applied to successive layers of powdered material,” Tsu-Raun tells us. “It is relatively fast and produces parts in production thermoplastics, but is less accurate than PolyJet." The method is also really good at making complex shapes with awesome surface finishes. One of the main differences is that MJF uses a polymer powder and a fusing system (ink agents and infrared frequencies) to cure parts.
How Xometry Can Help
Taking advantage of our 3D printing services—of which there are many—can not only give you one less thing to worry about, but also save you some money. Contact one of our representatives to learn how (or if you have any questions), or go ahead and upload your designs to the Xometry Instant Quoting page for a quick and free, no-obligation quote.
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