throughout the part. So even though MJF is slightly less accurate than SLS on small
part features, those features will be more robust.
MJF is also much faster than competing processes. Rather than tracing each
individual detail in a build layer, MJF scans the entire surface on each pass at a
consistent rate, regardless of how many parts are in that layer (similar to how a laser
printer prints each page in a document). Depending on what’s being 3D printed, this
provides build speeds several times that of competing technologies, even with larger
quantities. To understand what impact this might have on your project, simply upload
the CAD file and compare the quoted lead time and price to Protolabs’ other 3D
printing or machining services.
Design Elements to Consider
Many of the design principles applied to SLS and even injection-molded parts are just
as relevant to MJF:
• Thin-walled or large, flat surfaces should be reinforced with ribs or gussets, and holes
surrounded with raised bosses wherever possible.
• Raised text and cosmetic part features smaller than 0.020 in. (0.5 mm) might not
survive secondary post-processing. Check the design for manufacturability analysis
that accompanies your part quote for details.
• Wall thicknesses from 0.1 to 0.5 in. ( 2. 5 to 12. 7 mm) are ideal. Get much above or
below this and part tolerances may be affected.
• MJF does a great job with assemblies, living hinges, snap fits, and pin hinges.
• As with any 3D printing process, MJF produces some stair-stepping on oblique
angles. Cosmetic surfaces should be clearly identified on the part drawing or digitally
in the product manufacturing information (PMI), so the manufacturer can attempt to
orient the parts in the build chamber accordingly.
• Protolabs (or any well-equipped manufacturing operation) can install heat-stake
threaded inserts and metal bushings in MJF parts. And in addition to dying parts
black, application of primer paint is also offered.
Sound familiar? As mentioned at the start of this design tip, MJF is similar in many
ways to other additive manufacturing technologies, offering predictable part quality and
possessing design rules that are well understood. What’s different is its unique ability
to make accurate parts with isotropic mechanical properties, and in many cases do
so more quickly than other 3D printing methods. Together, these attributes have the
potential to make MJF an additive game-changer.
And although MJF is limited
to PA12 nylon (Figure 2) at
this time, Protolabs and HP are
regularly investigating additional
materials, including flame-retardant and glass-filled nylon,
elastomers, and multiple colors
in a single build. This may be a
good time to consider what role
MJF can play in your current
and future part development
At a glance: MJF vs. SLS
Figure 2. Multi Jet Fusion parts are 3D printed in a natural gray
Nylon 12 material, however, parts can be easily dyed jet black
(as pictured) for improved cosmetic appearance.