Stereolithography vs. PolyJet:
Photopolymer 3D Printing
Materials and Applications
What is the difference between these two popular 3D printing technologies?
Stereolithography and PolyJet are often grouped together beneath the photopolymer branch of additive
manufacturing. While it is true both 3D
print technologies share a similar printing
foundation -- they both use UV energy
to cure liquid photopolymer -- PolyJet
and Stereolithography involve dissimilar
print methods to achieve a fully cured end
product. These build style variances mean
PolyJet and Stereolithography are not always
suited for the same types of applications.
Understanding their differences will guide
you toward using each process for the right
application rather than force fitting one
photopolymer process to meet every project.
The main differences between PolyJet
and Stereolithography are part resolution,
manufacturing speed, part size, materials
Process Overview: How it Works
Also known as vat photopolymerization,
Stereolithography 3D prints designs within
a bed of liquid plastic. A thin layer of resin
is evenly spread across the build platform.
UV energy, directed via dynamic mirrors,
cures a cross-section of the design including
supports to anchor the design to the build
platform and protect delicate features. Once
a layer is cured, the build surface shifts
downward and a thin layer of resin is applied
to the last layer. This process continues, layer
Stereolithography prints in a resolution, or
layer thickness, around 0.002” at its smallest
and 0.005” for designs that don’t require
specific resolutions. Stereolithography parts
are built in a “green state,” meaning they are
not fully cured during printing; rather, parts
complete curing in a UV oven after excess
resin has been removed.
PolyJet does not 3D print parts in a vat of
resin. Instead, it prints parts similar to a 2D
printer. Fine print nozzles deposit droplets
of plastic photopolymer material coupled
with water-soluble support material onto a
clean build platform. The plastic is deposited
and cured simultaneously by UV energy,
which concentrates around the nozzle head.
Once a layer is complete, the build platform
descends and the next layer is deposited
and cured on top of the first. This process
repeats, layer by layer, until the final product
is achieved. PolyJet prints in the finest layer
Figure 1: Dynamic mirrors direct UV energy in precise designs.
Figure 2: UV lasers move quickly across the design, curing each layer. This design prominently
showcases supports to anchor the part to the build platform and ensure an accurate build.