Multi Jet Fusion, or MJF, is a professional-grade 3D printing technology that uses powder to create objects. HP developed and introduced this technology. Its main goal is to quickly make strong, working nylon parts that work well for both testing new designs and making final products. Unlike many other 3D printing methods, MJF was built from the start to be fast, make high-quality parts, and work efficiently for production. As we look at manufacturing in 2025, MJF has become a top choice for creating complex, long-lasting plastic parts in large quantities. This guide gives you a complete overview of the technology, how it works, what materials it uses, and how businesses use it.
The MJF Printing Process
To really understand what is MJF 3D printing, we need to first explain how it turns computer files into real objects. The technology uses heat to melt polymer powder layer by layer, but its special way of applying energy and binding liquids is what makes it different. The main idea is to put special liquids selectively onto a bed of powder and then melt an entire layer all at once. This is different from laser systems that work point by point. This whole-area melting approach is why MJF is so fast and why its parts have consistent strength.
The Printing Cycle
Making a part follows a precise, repeating cycle. Each layer, usually only 80 microns thick, is formed through four main steps.
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Material Coating: A spreading arm moves across the build area, putting down a thin, even layer of polymer powder, such as PA 12, onto the build platform.
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Agent Jetting: A printhead, similar to those in regular paper printers but much more complex, passes over the powder bed. It carefully sprays thousands of tiny droplets of two different liquids:
- Fusing Agent: This is a dark-colored liquid that conducts heat well. It is precisely placed onto the areas of powder that will become the solid part. Its job is to absorb heat energy.
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Detailing Agent: This liquid is sprayed around the edges of the part. It has properties that stop melting, acting as a coolant and making sure edges are sharp and fine details are clear.
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Energy Application & Fusing: A high-power heat source passes over the entire build area. The powder coated with the fusing agent absorbs this heat energy, quickly melting and joining into a solid layer. The surrounding powder, along with areas treated with the detailing agent, stays unmelted.
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Layer Completion: The build platform lowers, and the process starts again with a new layer of powder. The part is built layer by layer, completely surrounded and supported by the loose, unmelted powder in the build chamber.
The Post-Processing Workflow
Once the printing is complete, the entire build unit, containing the block of melted parts and unmelted powder, is moved to a separate processing station. The work is not finished. First, the unit must cool down for a controlled period. This gradual cooling is important for getting the best strength properties and preventing part warping. After cooling, the parts are dug out from the loose powder. This unmelted powder is then collected, filtered, and mixed with fresh material for future builds. The parts themselves go to a bead blasting or sandblasting station, where high-pressure media removes any remaining powder, showing a matte grey, slightly rough surface finish. From here, parts can be used as-is or go through additional processes like dyeing for color or vapor smoothing for a sealed, injection-mold-like finish.
MJF Materials and Components
How well an MJF part performs is directly connected to the materials used. While there are fewer material choices than other technologies, the available options are designed for strong, real-world uses. As of 2025, the system is dominated by high-performance polyamides and flexible elastomers.
Primary Thermoplastic Powders
- PA 12 (Polyamide 12): This is the main material for MJF. It is known for making strong, stiff parts with excellent resistance to chemicals like oils, greases, and hydrocarbons. Its ability to keep its shape and reproduce fine details makes it an ideal choice for a wide range of working components, from cases and brackets to complex assemblies. PA 12 offers a tensile strength typically in the range of 48-50 MPa, making it suitable for mechanically demanding roles.
- PA 11 (Polyamide 11): A more flexible and impact-resistant alternative to PA 12. PA 11 is made from a renewable resource (castor oil), giving it a more sustainable profile. It is the preferred material for applications requiring high toughness and resistance to cracking under stress or impact, such as living hinges, snap-fit components, and athletic equipment.
- TPU (Thermoplastic Polyurethane): This is a flexible, rubber-like material that enables the production of stretchy parts. With its high tear strength and excellent bounce-back, TPU is used to create parts like seals, gaskets, protective lattices, flexible hoses, and shock absorbers. It opens up applications that require both durability and flexibility.
The Role of Agents
The fusing and detailing agents are the special liquids that control the melting process. They are the "secret ingredient" of what is MJF 3D printing. In simple terms, the fusing agent acts as a heat-absorbing ink, defining the shape of the part. The detailing agent works as a boundary-defining coolant, preventing heat from spreading into surrounding powder and ensuring that edges are crisp and separate features do not melt together. This two-agent system gives the process its precision and control over the final part properties.
Key Advantages and Disadvantages
Like any manufacturing technology, MJF has a clear set of strengths and weaknesses. A balanced understanding is important for determining if it is the right solution for a given project. We find its value is clearest when speed, cost-per-part in a batch, and mechanical performance are the main drivers.
Advantages
- Excellent Mechanical Properties: Parts are nearly isotropic, meaning they show consistent strength in the X, Y, and Z directions. This is a significant advantage over layered technologies like FDM.
- High Production Speed: The ability to melt an entire layer at once makes MJF one of the fastest 3D printing technologies for producing batches of parts.
- Complex Design Freedom: Because parts are supported by the surrounding powder, there is no need for dedicated support structures. This allows for the creation of complex internal channels, complex shapes, and consolidated assemblies.
- High Detail and Accuracy: The combination of fine powder and precise agent spraying allows for high-resolution features and reliable dimensional accuracy.
- Cost-Effective Batches: A high powder refresh rate (typically around 80% reusable powder to 20% virgin powder) minimizes waste and drives down the cost-per-part, especially for nested, medium-volume production runs.
Disadvantages
- Limited Material Selection: As of 2025, the material portfolio is still primarily focused on nylons and TPU, which is narrower than technologies like FDM or SLS.
- Initial Surface Finish: Parts come out of the printer with a standard matte grey color and a slightly rough texture. Post-processing is required to achieve a smooth surface or a specific color like black.
- High Initial Equipment Cost: The machinery is industrial-grade and represents a significant money investment, making it more suited for service companies and large businesses than small businesses or individuals.
- Mandatory Cooling Time: The build unit requires a cooling period that is often longer than the print time itself. This extends the total lead time from file to part-in-hand.
MJF vs. Other Technologies
To fully appreciate MJF, it is helpful to position it relative to other leading 3D printing technologies. Each process has a distinct sweet spot, and understanding these differences is key to making the right manufacturing choice.
Comparison Table
| Feature | Multi Jet Fusion (MJF) | Selective Laser Sintering (SLS) | Fused Deposition Modeling (FDM) | Stereolithography (SLA) |
|---|---|---|---|---|
| Process | Agent jetting & thermal fusion | Laser sintering of powder | Extrusion of thermoplastic filament | UV curing of liquid resin |
| Primary Materials | Nylons (PA11, PA12), TPU | Wide range of nylons, PEEK | PLA, ABS, PETG, many more | Photopolymer resins |
| Best For | Functional prototypes, end-use parts | Functional prototypes, complex parts | Low-cost prototypes, large parts | High-detail cosmetic prototypes |
| Key Strength | Speed, isotropic properties | Material variety, no supports | Low cost, large material choice | Superior surface finish |
| Key Weakness | Limited material choice, grey finish | Slower than MJF, porous surface | Anisotropic parts (weak layers) | Brittle parts, requires post-curing |
The Critical MJF vs. SLS Difference
The most frequent comparison is between Multi Jet Fusion and Selective Laser Sintering (SLS), as both are powder bed fusion technologies. The basic difference lies in the energy source and application method. SLS uses a high-powered laser to trace the cross-section of a part, melting the powder point by point. MJF, in contrast, puts a fusing agent across the entire cross-section and uses a flat infrared lamp to melt the whole layer in a single pass. This area-wide process is what gives MJF its speed advantage, particularly when printing a large number of small parts nested in the build volume. This method also tends to distribute heat more evenly, contributing to the consistent, isotropic properties of the final parts.
Beyond Prototypes in 2025
By 2025, the conversation around what is MJF 3D printing has clearly shifted from a prototyping tool to a workable production solution. Its ability to deliver durable parts quickly and cost-effectively has unlocked new manufacturing strategies.
Case Study: Bridge Manufacturing
- The Challenge: An automotive supplier needs 500 custom air ducts for a pre-production vehicle line. The lead time for injection molding tools is 12 weeks, threatening project delays.
- The MJF Solution: Using MJF, we can produce all 500 functional, durable PA 12 ducts in under a week. This "bridges the gap" between the final prototype and full-scale production. The resulting air ducts are not only dimensionally accurate but also show a uniform, slightly textured finish that is professional and durable enough to withstand under-hood temperatures. Unlike layered FDM parts, there is no risk of separation under pressure or vibration.
Case Study: JIT Medical Housings
- The Challenge: A medical device company offers customized housings for a handheld diagnostic tool. Holding physical inventory for dozens of potential variations is financially prohibitive.
- The MJF Solution: The company adopts a just-in-time (JIT) manufacturing model, using MJF to print housings on-demand as orders are placed. This eliminates warehousing costs and enables mass customization. The consistency of the MJF process ensures that a part printed today is identical to one printed six months from now, which is critical for regulated medical products. The PA 12 material is easily sterilized and robust enough for a clinical environment.
A Guide to Choosing MJF
Deciding to use MJF is a strategic choice based on volume, complexity, and performance requirements. It is not always the best tool for the job, but in its sweet spot, it is often unbeatable. We use this checklist to guide engineering and business decisions.
When to Choose MJF
- You need part quantities from 10 to 10,000 units. This is the ideal range where MJF is faster and more economical than CNC machining or early-stage injection molding.
- Your parts have complex internal channels, organic shapes, or lattice structures. The support-free nature of the process makes these shapes possible without added cost or post-processing hassle.
- Consistent mechanical strength in all directions (isotropy) is a non-negotiable requirement for your application.
- Speed for an entire batch of parts is more critical than the surface finish of a single part out of the printer.
- You are creating custom jigs, fixtures, end-of-arm tooling, or other factory automation components. The durability and speed of MJF make it a dominant technology for this industrial application in 2025.
In conclusion, what is MJF 3D printing is a question with a clear answer: it is a production-oriented additive manufacturing technology. Defined by its speed, the strength of its nylon parts, and its unique support-free process, MJF has earned its place as a pillar of modern manufacturing. It excels at bridging the gap between prototyping and mass production and has enabled new business models through on-demand manufacturing and mass customization. As the technology continues to evolve, its role in creating the functional parts that power our world is only set to expand.