MJF 3D printing (HP Multi Jet Fusion) is our go-to process for strong, functional nylon and TPU parts. It builds dense, isotropic parts with fine detail at a low cost per part, which makes it equally useful for functional prototypes and for production runs from a single part to thousands, with no tooling. Our shop is in Coopersville, Michigan, just west of Grand Rapids, and we ship parts nationwide.
How MJF 3D Printing Works
HP introduced Multi Jet Fusion in 2016, building on its decades of inkjet printing experience. MJF is a powder bed process, but unlike SLS it does not use a laser.
- A thin layer of nylon or TPU powder is spread across a heated build bed.
- An inkjet print head with 30,000 nozzles jets a fusing agent wherever the part needs to be solid, and a detailing agent around the edges to keep contours sharp.
- High-power lamps pass over the bed. The areas with fusing agent absorb the heat and melt, forming one layer of the part.
- The process repeats layer by layer until the build is complete.
- The build unit cools in a separate station for several hours, then each part is removed, cleaned of loose powder, and bead blasted.
For a full walkthrough with video of each step, see How It Works: HP Multi Jet Fusion 3D Printing.
When to Choose MJF 3D Printing
- Speed: MJF fuses an entire layer in one pass instead of tracing each part, so build time barely changes as more parts are added. That makes it several times faster than SLS or SLA for full builds.
- Strength in every direction: parts have consistent mechanical properties in X, Y, and Z, so orientation matters far less than with FDM or SLA.
- Finer detail than SLS: smaller features and sharper edges.
- No tooling: production can start as soon as your file is approved, and design changes only need a new CAD file.
- Air and fluid tight: Nylon 12 parts hold pressure right off the machine, with no sealing.
MJF vs. Injection Molding and Urethane Casting
For low volumes, tooling cost and lead time often decide whether a part gets made at all. With injection molding, every complex feature, insert change, or engineering change adds cost to the mold, and customizing parts usually means a secondary operation.
With MJF, part complexity has almost no effect on price. Cost is driven by part volume, quantity, and machine time. MJF is most cost-competitive for nylon parts around 6″ × 3″ × 6″ or smaller, though larger parts can still make sense. Bigger parts can also be printed in sections and bonded.
With MJF you can:
- Skip draft angles
- Print internal channels for air, fluid, or wiring
- Use features that cannot be molded or machined
- Serialize or customize every part with text, logos, or geometry changes
- Change the design between runs with no tooling cost
For more, see 3D Printing for Low Volume Production.
MJF 3D Printing Capabilities
| Build volume | 14.75″ × 11″ × 15″ (larger parts can be printed in sections and bonded) |
| Layer thickness | 0.003″ (0.08 mm) |
| Minimum feature size | 0.020″ (0.5 mm) |
| Accuracy | ±0.010″ for the first inch, ±0.005″ per inch thereafter (see our part accuracy page) |
| Print resolution (X, Y) | 1200 dpi |
| Standard finish | Bead blasted and dyed black, at no extra charge |
| Quantities | One-off prototypes through production runs |
| Build preparation | Materialise Magics with Build Processor for MJF |
Accuracy depends on part size and geometry. Send us your CAD file and we will give you a realistic estimate for your part.
MJF 3D Printing Materials
Each material has its own page with full mechanical properties, certifications, data sheets, and part photos.
| Material | Best for | Key properties |
|---|---|---|
| Nylon 12 (PA-12) | Functional prototypes, production parts, housings, fixtures, air- and fluid-tight parts | Tensile strength 6,960 psi (48 MPa), 20% elongation, HDT 347°F (175°C) at 66 psi, biocompatible |
| PA-12 Glass Beads (PA-12 GB) | Stiff housings and enclosures, higher-temperature parts, and prototypes of glass-filled molded parts | Tensile modulus up to 392 ksi (2,700 MPa), HDT 347°F (175°C) at 66 psi, 40% glass bead filled |
| TPU M95A | Gaskets, seals, grips, vacuum cups, bumpers, lattice cushioning | 90 Shore A, high elongation, good tear and abrasion resistance |
Not sure which to use? Our team can recommend a material based on how the part will be used. Also see our chemical compatibility data and strength and wear testing.
Finishing Options for MJF Parts
MJF parts come off the machine light gray. Our standard finish is bead blasted and dyed black at no extra charge. Other options include:
- Raw gray (bead blasted only)
- Vapor smoothing
- Semi-gloss polished finish
- Cerakote
- Sanding and painting
- Heat-set inserts, tapping, and other secondary operations
See all finishing and post-processing options.
Designing Parts for MJF: Our Design Guide and Test Data
Forerunner 3D Printing is an engineering-led additive manufacturer. Our sister company, DeWys Engineering, has a team of mechanical engineers designing parts for MJF every day, for our customers and for our own products. Over the years they have printed, broken, and measured a lot of parts, and every lesson learned went into one internal reference.
That reference is our HP Multi Jet Fusion Part Design Guide. It is the same guide our own engineers use, and we publish it so anyone designing for MJF can benefit from it. Most MJF design advice online is generic. This is real data from real parts, so your prototypes start closer to a production-ready design.
What the design guide covers
- Saving out high-quality part files
- Minimum feature sizes
- Designing text and logos that print cleanly
- Dimensional accuracy and how to design for it
- Part structure options
- De-powdering holes and internal passageways
- Assembly features: snap fits, dowels, glue joints, and tape
- Printed threads, tapped threads, and threaded inserts
Test data from our own MJF parts
These pages document tests we ran in our shop, with real numbers you can design to:
| Resource | What you get |
|---|---|
| Threads in 3D printed parts | How to model NPT and NPS threads in CAD so they print and seal |
| Dowel hole design guide | Five rules for designing dowel holes and slots |
| Heat-set inserts | How to size holes for and install heat-set inserts in MJF parts |
| E-Z Lok inserts in TPU | Pull-out strength testing in flexible MJF parts |
| Glue strength guide | Bond strength of adhesives on PA-12, TPU, and other materials |
| Double-sided tape testing | Holding strength of tapes on printed surfaces |
| Pressure vessel testing | Burst testing of sealed MJF parts, up to 600 psi |
| Wear and strength examples | Real-world strength and wear results on MJF parts |
| Chemical compatibility of PA-12 and PA-12 GB | How Nylon 12 holds up to common shop chemicals |
| Part accuracy | Tolerances to expect for MJF and other processes |
Have a design question the guide does not answer, or a part that isn’t ready to print yet? Our design for additive manufacturing services can help, from design review to full CAD design. You can also send us your CAD file, and our sales engineers will review it for printability before we quote it.
MJF Part Examples
Production and end-use parts
See how MJF is used for low volume production.
Manufacturing aids and end-of-arm tooling
See how MJF parts are used in end-of-arm tooling.
Prototypes and one-off parts
More examples: black dyed MJF parts and raw gray MJF parts.
MJF 3D Printing FAQ
How strong are MJF parts?
MJF parts are strong enough for functional and production use. Nylon 12 has a tensile strength of about 6,960 psi (48 MPa) with 20% elongation, and MJF parts have consistent properties in X, Y, and Z, so orientation matters far less than with FDM or SLA. For extra stiffness, PA-12 Glass Beads has a tensile modulus of 406 ksi (2,800 MPa). See our strength and wear examples for real-world results.
How big can MJF parts be?
Up to 14.75″ × 11″ × 15″ in one piece. Larger parts can be printed in sections and bonded. MJF is most cost-competitive for parts around 6″ × 3″ × 6″ or smaller.
How accurate are MJF parts?
Plan on ±0.010″ for the first inch and ±0.005″ per inch thereafter. Accuracy depends on part size and geometry; see our part accuracy page for details by process.
Are MJF parts watertight?
Yes. Nylon 12 MJF parts hold air and fluid pressure right off the machine, with no sealing. See our pressure vessel testing for burst test results up to 600 psi.
What color are MJF parts?
MJF parts come off the machine light gray. Our standard finish is bead blasted and dyed black at no extra charge. We can also leave parts raw gray, or vapor smooth, polish, Cerakote, or paint them.
Is MJF or SLS better for my part?
Both make strong nylon parts without supports. MJF is usually faster and more economical for small to medium parts, with finer detail. SLS is the better choice for larger parts, white parts, and glass-filled nylon. Send us your file and we will recommend the best fit.
Is MJF cost-effective compared to injection molding?
For low to medium volumes, often yes. MJF needs no tooling, part complexity has almost no effect on price, and design changes only need a new CAD file. See 3D Printing for Low Volume Production for more.
ISO 9001:2015 Certified Quality
MJF is often used for functional prototypes, bridge manufacturing, and low-volume production, where consistency between parts matters as much as the parts themselves. Our quality management system is certified to ISO 9001:2015 and covers engineering, additive manufacturing, post-processing, and inspection, so customer requirements and documentation are handled consistently from quote to delivery.