Micah Chaban is the founder and Vice President of Sales at RapidMade, a leader in additive manufacturing solutions. With years of experience in industrial 3D printing, Chaban has helped businesses integrate cutting-edge technology into their production processes, delivering high-precision parts across various industries. Under his leadership, RapidMade has become a go-to resource for companies looking to optimize design, manufacturing, and post-processing in HP Multi Jet Fusion 3D printing.
In this conversation, Chaban breaks down the key factors that influence accuracy and surface finish in HP Jet Fusion printing, shares expert design tips, and explains how manufacturers can achieve superior results without excessive post-processing.
What makes HP Jet Fusion stand out in terms of accuracy and precision?
HP Jet Fusion is one of the most precise and repeatable additive manufacturing processes available today. It consistently achieves tolerances of about ±0.2 mm per 100 mm, which is comparable to injection molding. What sets it apart is its ability to produce high-resolution parts with strong mechanical properties at industrial speeds. Unlike FDM or SLA, where layer adhesion can introduce weak points, MJF prints parts with near-isotropic strength, meaning they perform just as well in all directions.
What are the biggest factors that affect dimensional accuracy in MJF?
Dimensional accuracy comes down to three main factors: material properties, part orientation, and heat management. The nylon powders used in MJF expand and contract during the printing and cooling process, which can introduce minor shrinkage if not accounted for. That’s why part orientation is critical—certain features print more accurately in the XY plane than in the Z-axis due to how the powder fuses. Additionally, uniform wall thickness helps minimize warping. If a part has drastic variations in thickness, it can cool unevenly, leading to distortions.
How do you design parts to maximize precision and minimize dimensional inconsistencies?
A few design strategies make a big difference. First, keeping small features aligned in the same plane reduces Z-axis variability. Second, using smooth transitions rather than abrupt geometry changes helps maintain uniformity during fusing. Also, avoiding long, thin features with high aspect ratios—anything over 10:1—helps prevent warping. Finally, adjusting for shrinkage during the design phase ensures that final dimensions match the intended specifications. We often run test prints to fine-tune these variables before full-scale production.
What about fit and assembly? How should designers approach tolerances for interlocking parts?
For interlocking components, clearance and interference fits are key. MJF parts tend to expand slightly during cooling, so allowing proper spacing is crucial. We recommend at least 0.4 mm clearance for mating parts to ensure a proper fit. For moving parts, a 0.7 mm clearance is best to prevent unintended fusion during printing. If designing snap-fit features, material flexibility plays a role—some designs need a little more or less interference depending on how rigid the final part needs to be.
Surface finish is another major concern for manufacturers. What are the main challenges with MJF parts?
Like all layer-based 3D printing methods, MJF produces slight texture variations due to its powder fusion process. The primary challenge is reducing visible layer lines, especially on sloped or curved surfaces. The default 80-micron layer thickness is fine enough to minimize stepping, but part orientation plays a big role. Surfaces at angles below 20 degrees to the print bed tend to show more stair-stepping effects.
Another challenge is powder adhesion. The unsintered powder can leave a slightly rough texture on surfaces, particularly on upward-facing areas. That’s where post-processing comes into play—techniques like bead blasting, dyeing, and vapor smoothing can significantly enhance the final appearance.
What are the best design practices for achieving a smoother surface finish?
A few design tweaks can make a big difference in surface quality. First, keeping critical surfaces above a 20-degree incline reduces visible layer lines. Second, using fillets and chamfers instead of sharp edges helps blend layer transitions more smoothly. We also advise avoiding unnecessary ridges and thin ribs, as they tend to exaggerate layering artifacts.
If aesthetics are a top priority, post-processing is often necessary. Simple design adjustments can reduce the need for extensive finishing, but techniques like vapor smoothing give the best results for a truly polished look.
How do you choose the right post-processing method for MJF parts?
It depends on the application. If a part just needs a basic cleanup, bead blasting is usually enough to remove excess powder and slightly smooth out the surface. For customers who need a uniform color, dyeing is a great option—it integrates with the material and doesn’t affect surface texture like paint might.
For a high-end, polished finish, vapor smoothing is the best option. This chemical process slightly melts the surface, sealing the outer layers and significantly reducing roughness. It also improves water resistance, making it ideal for applications where sealing is important. However, vapor smoothing can slightly alter part dimensions, so we factor that into our design adjustments.
Can MJF parts achieve the same finish quality as injection-molded parts?
MJF parts can achieve a finish quality similar to injection molding, but with some limitations. While the raw print has a slightly rougher surface due to the powder-bed process, post-processing techniques like vapor smoothing and dyeing can significantly enhance the finish. Vapor smoothing, in particular, seals the surface and reduces roughness, creating a texture that is much closer to molded plastics.
However, the range of available finishes is more limited compared to injection molding. With molding, a variety of textures, gloss levels, and coatings can be applied directly during production. In MJF, achieving a highly polished or specialty surface requires additional hand-finishing techniques, such as sanding and painting, which add time and cost. For most applications, bead blasting, dyeing, and vapor smoothing provide an excellent balance of aesthetics and performance, but if a specific texture or gloss level is needed, additional manual processing may be required.
How does material selection impact accuracy and surface finish?
Different materials behave differently during printing. PA12 is the most commonly used because it offers the best balance of strength, accuracy, and surface quality. It has minimal shrinkage and good mechanical properties, making it the best choice for functional parts. PA11 is slightly more flexible and impact-resistant but requires more post-processing to achieve a smooth surface. TPU is great for rubber-like parts, but since it’s flexible, it can introduce different accuracy challenges.
For companies looking to transition to MJF, what’s the biggest piece of advice you’d give?
Understand that additive manufacturing requires a different design mindset. Traditional manufacturing limits design complexity, whereas MJF thrives on it. Taking advantage of lattice structures, complex geometries, and lightweighting strategies will make the most of what the technology offers. Also, prototyping is key. Running test prints before full production allows us to fine-tune accuracy and surface quality for the best possible results.
How can manufacturers get started with high-precision HP Jet Fusion printing?
The best way is to work with a team that understands both design and production. At RapidMade, we help customers optimize their designs for MJF, ensuring they get the best possible accuracy and surface finish. Whether it’s prototyping, small-batch production, or full-scale manufacturing, we guide clients through every step—from CAD optimization to post-processing.
For expert guidance and high-quality HP Jet Fusion printing, reach out to us at RapidMade.com or email us at [email protected]. We’re happy to help bring your designs to life with precision and efficiency.
