Design Tips for 3D Printing Functional
Parts with the Multi Jet Fusion Process
An early adopter shares some practical advice on how this new manufacturing
technology can be used to create durable prototype and end-use production parts
If you’re familiar with selective laser sintering (SLS) design
principles, you’re already close to being an MJF master. Both
are powder-bed 3D printing technologies, using a heated
chamber, the entirety of which can be used for making
parts—there’s no need for supports as there is with other 3D
printing processes. While SLS uses a laser to fuse individual
powder layers, MJF (Figure 1) uses an infrared heating
element together with proprietary fusing and detailing agents.
Regardless of the actual manufacturing process, MJF
produces fine features and more consistent isotropic material
properties, and is suitable for complex, low-volume quantities
of parts like brackets and clips, mechanical assemblies,
component housings, and durable but accurate jigs and
How MJF is Different
• Resolution: MJF prints in layers 0.003 in. (80 microns)
thick, and boasts a minimum feature size of 0.020 in.
(0.5mm). This is finer than the 0.030 in. (0.75 mm)
produced with SLS, but MJF-produced part details are a bit
more variable at this size range, with expected tolerances
of +/-0.004 (0.10 mm) over the first inch vs. +/-0.001
(0.025 mm) for SLS. Be aware that these tolerances will
vary depending on part size and geometry, so pay particular
attention on designs that require tight clearance such as
housings or multiple mating parts in an assembly.
• Part Size: At 11.1 in. by 14. 9 in. by 14. 9 in. (284 mm by
380 mm by 380 mm), MJF’s maximum build envelope is a bit
smaller than the 19 in. by 19 in. by 17 in. size available with
many SLS machines. This means the maximum dimensions
of any individual MJF-generated part cannot exceed 13. 5 in.
by 10. 4 in. by 13. 7 in. (343 mm by 264 mm by 348 mm),
although this is plenty big for many 3D-printed parts.
• Materials: Because MJF currently prints only unfilled
Nylon 12 (PA12), SLS has a slight edge in terms of
available materials and colors (for now). However, Nylon
12 provides a breadth of mechanical or thermal properties
that are often required of functional parts and in end-use
applications. If cosmetics are important, we suggest dying
the natural salt-and-pepper gray of MJF parts black (which
Protolabs does in-house), and also recommend a light
bead blast for parts made with either MJF or SLS.
Stronger Parts, Faster Process
It’s also important to consider areas in which MJF excels.
For starters, MJF builds strong parts, with tensile strength
at the upper end (maximum load: XY and Z 48 MPa/6,960
psi with ASTM D638 method) of what’s possible with SLS.
More important, MJF produces more consistent mechanical
properties in each direction of the part geometry—far
more so than other powder-based printers—a factor that’s
especially desirable with multi-faceted, complex designs
where strength and reliability is required everywhere
Technology giant HP has developed and launched Multi Jet Fusion (MJF), an industrial-grade 3D
printing technology that quickly and accurately
produces functional prototypes and end-use parts
for a variety of applications. Protolabs served as one
of several test sites for this additive manufacturing
process because of its experience in industrial 3D
printing, and recently added HP Jet Fusion 3D 4200
printers to its suite of manufacturing tools. Here
are several considerations to keep in mind when
designing for MJF.
Case in Point
Figure 1. Multi Jet Fusion selectively applies
fusing and detailing agents across a bed of
nylon powder, which are fused in thousands
of layers by heating elements into solid