HP’s Multi Jet Fusion 3D printing technology has revolutionized additive manufacturing with its ability to produce strong, high-resolution parts at unprecedented speeds. Unlike other powder-based methods like selective laser sintering (SLS), MJF doesn’t rely on a laser to fuse material. Instead, it selectively deposits fusing and detailing agents, then applies infrared heat to solidify each layer. This process allows for faster production cycles, smoother surface finishes, and near-isotropic mechanical properties, making it ideal for functional end-use parts.
However, just because MJF offers greater design freedom than traditional manufacturing methods doesn’t mean every design will yield optimal results. Engineers must follow best practices in material selection, part geometry, and post-processing to ensure high part quality and consistency.
“MJF offers more design freedom than injection molding or even other types of 3D printing, but it’s not rule-free,” says Micah Chaban, founder and vice president of sales at RapidMade, a company specializing in industrial additive manufacturing. “To get the best part quality and consistency, you need to understand how the material behaves during printing and how factors like wall thickness, orientation, and post-processing affect the final product. When designers work with the technology instead of against it, that’s when we see the best results.”
Choosing the Right Material for the Job
HP Jet Fusion primarily supports engineering-grade thermoplastics, each with unique mechanical properties suited for different applications.
Nylon PA12 is the most commonly used material, offering high strength, rigidity, and chemical resistance, making it ideal for mechanical components and load-bearing applications. Nylon PA11 provides greater flexibility and impact resistance, making it a better choice for snap-fit assemblies and parts subject to repeated stress. TPU (thermoplastic polyurethane) is a rubber-like material well suited for seals, gaskets, and protective enclosures.
“Material selection is one of the first things we discuss with clients,” Chaban says. “Choosing the strongest material isn’t always the right move—flexibility, heat resistance, and post-processing requirements all factor into the decision.”
Engineering for Strength and Stability
MJF’s high-speed printing process allows for rapid production, but the quick cooling cycle can introduce stress into the part. Engineers must account for this when designing wall thicknesses, cantilevered structures, and thin sections to prevent warping and ensure durability.
A minimum wall thickness of 0.3 millimeters is recommended for small features, while vertical walls should be at least 0.5 millimeters thick. Hollow parts should maintain a minimum thickness of 2 millimeters to ensure structural integrity.
Long, unsupported features such as cantilevers require additional consideration. For small cantilevers, the aspect ratio should remain below 1:1 (length to width), and longer overhangs should incorporate reinforcing ribs or fillets to prevent sagging.
“When people design for injection molding, they assume thin walls are fine because the material flows into every corner of the mold,” Chaban explains. “With MJF, you’re fusing powder together, and if the walls are too thin, they won’t fuse properly or will warp. You have to balance material efficiency with printability.”
Tolerances and Moving Assemblies
One of the biggest challenges in designing for MJF is ensuring precise fitment in assemblies. Because MJF parts can exhibit slight variations due to thermal effects and powder expansion, engineers must allow for proper clearances in mating components.
Mating parts should have a minimum clearance of 0.4 millimeters, while snap-fit features should include a slight interference fit to maintain a secure connection. Moving parts require at least 0.7 millimeters of clearance to prevent fusing during the printing process.
“You can’t assume machining tolerances will work for 3D printing,” Chaban says. “If you don’t account for how the material behaves, your parts won’t assemble correctly. Testing and iteration are key.”
Lightweighting Without Compromising Strength
One of MJF’s biggest advantages is its ability to produce lightweight yet strong components through techniques such as hollowing, lattice structures, and topology optimization.
Hollowing reduces material usage and print time, but proper design is essential to maintain mechanical integrity. A hollow part should have walls at least 2 millimeters thick, with drain holes (minimum 5 millimeters in diameter) to allow unfused powder to escape.
Lattice structures provide an effective way to reduce weight while maintaining load-bearing capacity. These structures must be designed with adequate spacing—typically 5 millimeters or more—to ensure proper powder removal.
“We’ve seen companies cut weight by as much as 50 percent without sacrificing performance,” Chaban says. “But if you don’t strategically reinforce key stress areas, you risk reducing durability instead of just mass.”
Achieving High Accuracy and Superior Surface Finish
MJF can achieve tolerances comparable to injection molding, but certain design decisions affect dimensional accuracy. Placing critical features in the same plane reduces warping, while embossed or engraved details should be at least 1 millimeter deep for clear definition.
HP Jet Fusion naturally produces a smoother finish than SLS, but some layer lines remain visible. Engineers can minimize stepping effects by avoiding shallow angles below 20 degrees, which tend to exaggerate the appearance of layers.
For applications requiring even better surface quality, post-processing techniques like bead blasting, dyeing, and vapor smoothing improve both aesthetics and performance.
Designing for Manufacturing Success
HP Jet Fusion offers a compelling alternative to traditional manufacturing, but designing for success requires a shift in mindset.
“MJF isn’t just a replacement for machining or molding—it’s its own thing,” Chaban says. “The companies that embrace its capabilities and design accordingly get the best results. Those that try to apply old manufacturing constraints to 3D printing tend to struggle.”
By following best practices in material selection, wall thickness, assembly tolerances, and surface finishing, engineers can take full advantage of MJF’s speed, precision, and cost-effectiveness.
For manufacturers looking to optimize their MJF designs, working with an experienced additive manufacturing partner can make all the difference theprimenames.com.
RapidMade specializes in HP Jet Fusion 3D printing, offering design consultation, prototyping, and production services. Visit RapidMade.com to learn more or request a quote.