Selecting the Right
Material for Industrial
3D Printing
Explore the material properties available with direct metal
laser sintering, elective laser sintering , and stereolithography
2 | Selecting the Right Material for Industrial 3D Printing
testing, shop floor use, and production.
And while the output of 3D printing
is different from that of other
manufacturing processes, it can offer
a suitable alternative when seeking a
direct replacement. Yet, its advantages
increase when users experiment with
the possibilities that it offers.
However, experimentation is a bit
challenging because of 3D printing’s
differences that extend beyond, but
are related to, material properties.
For example, additive materials lack
the rich set of performance data that
characterize a material over a range of
conditions. Instead, 3D printing users
are presented with a single data sheet
that contains a limited set of values.
Those values are also likely to present a
best case scenario based on testing of
virgin material (unrecycled powders), for
example.
Another complication is that 3D printing
produces anisotropic properties where
the values differ for the X, Y and Z axes.
The degree of anisotropism varies with
each additive technology—direct metal
laser sintering is the closest to isotropic,
for example—but it should always be a
consideration.
Materials must be suited to the application in order to have successful results.
The properties of any material become increasingly important as a product
progresses from concept and functional prototyping to production.
However, material properties can only be evaluated when the manufacturing
process is considered. It is the combination of the material and the process that
dictates the characteristics. For example, an alloy processed by die casting has
different properties when it is metal injection molded. Likewise, a thermoplas-
tic will have different properties if it is injection molded or CNC machined.
Additive manufacturing (AM), or 3D printing, is unique. It is different from all
other manufacturing processes, so the material properties and characteristics
of parts that it produces are different, even when using a nearly identical alloy
or thermoplastic.
Material
Advancements
In terms of material properties, it is not
a matter of being better or worse; it is
simply important to recognize that the
results will be different.
Recognizing that there is a difference,
the following information will aid in
the characterization, and ultimately the
selection, of materials from three widely
used industrial 3D printing processes:
direct metal laser sintering (DMLS),
selective laser sintering (SLS), and
stereolithography (SL).
The materials used in 3D printing have
been improving, as would be expected.
These advancements have allowed the
technology to move beyond models
and prototypes to functional parts for
3 | Selecting the Right Material for Industrial 3D Printing
However, the material suppliers rarely
publish material specifications that
document the change in properties
from one axis to another, as the data
behind these specifications can vary
greatly by material, process, and even
type of machine.
By designing for the 3D printing process
and adjusting the build orientation,
anisotropism or inadequate material
properties can be overcome. To do this,
leverage the experiences from past
projects or that of a qualified service
organization to fill in the data gaps that
exist because of the limited material
properties data. When performance is
critical, also consider independent lab
testing of additive materials.
While success is dependent on material
properties, they are not the only
considerations. Each additive material
and build process will also dictate
characteristics such as maximum part
size, dimensional accuracy, feature
resolution, surface finish, production
time, and part cost. So it is advised
to select a suitable material and then
evaluate its ability to meet expectations
and requirements related to time, cost,
and quality.
Generally, one or two material
properties distinguish an additive
material from all others. For example, if
seeking the average tensile strength of
polyamide (PA) 11, a stereolithography
photopolymer may be a better option
than a selective laser sintering PA.
Conversely, if the heat deflection
temperature (HDT) of an ABS is needed,
the best option would be a sintered
nylon.
Recognizing that a few properties
will separate one material from the
others, the recommended approach
for selecting a material for 3D printing
is to first define what mechanical or
thermal properties are critical. Then
review the material options to find a fit.
With the options narrowed, review other
remaining properties to determine if
the material will be acceptable for the
project.
Material
Selection
4 | Selecting the Right Material for Industrial 3D Printing
DMLS uses pure metal powders to
produce parts with properties that
are generally accepted to be equal
or better than those of wrought
materials. Because there is rapid
melting and solidification in a small,
constantly moving spot, DMLS may
yield differences in grain size and grain
boundaries that impact mechanical
performance. Research is ongoing to
characterize the grain structures, which
can change with the laser parameters,
post-build heat treatment, and hot
isostatic pressing. However, the results
are not widely available. Ultimately, this
difference will become an advantage
when grain structure can be
manipulated to offer varying
mechanical properties in a part.
Of the three additive manufacturing
processes discussed here, DMLS
produces parts with material properties
that approach an isotropic state.
However, there will be some property
variance when measured along
different axes.
Stainless steel is a commonly used
DMLS material, and it is available in two
grades at Protolabs: 17-4 PH and 316L.
Select 17-4 for its significantly higher
tensile strength (190 ksi vs. 70 ksi), yield
strength, and hardness (47 HRC vs. 26
HRC), but recognize that it has far less
elongation at break (EB) than 316L (8%
vs. 30%), which means that it will be
less malleable. Both 17-4 and 316L offer
corrosion resistance, but 316L is better
at resisting acids. 316L is also more
temperature resistant than 17-4. Note
that 17-4 may be heat treated to modify
mechanical properties, while 316L is
only offered in the stress-relieved state.
DMLS aluminum (Al) is comparable
to a 3000 series alloy that is used in
casting and die casting processes. Its
composition is AlSi10Mg. Al has an
excellent strength-toweight ratio, good
temperature and corrosion resistance,
and good fatigue, creep and rupture
strength.
Direct Metal
Laser Sintering
Since 3D printing is unique, a goal
of finding a perfect match to a cast,
molded or machined material is
ill-advised. Instead, investigate the
material options to find the material
that satisfies the most critical
requirements.
5 | Selecting the Right Material for Industrial 3D Printing
processing outside of Protolabs—
making it ideal for medical applications
such as dental implants.
Inconel 718 (IN718) is a nickel chromium
superalloy used in high service
temperature applications, such as
aircraft engine components. DMLS IN718
parts have an impressive operating
temperature range of -423°F to 1,300°F
coupled with excellent corrosion
resistance, and good fatigue, creep and
rupture strength.
DMLS IN718 has higher tensile
strength (180 ksi vs. 160 ksi) and
comparable yield strength (133 ksi vs.
160 ksi) than conventionally processed
IN718. However, its EB is half that of
conventionally processed IN718 (12% vs.
25%).
Compared to die-cast 3000 series
aluminum, the Al properties for tensile
strength (36 ksi to 43 ksi) and yield
strength (30 ksi to 32 ksi) far exceed the
average values. However, elongation
at break is significantly lower (1% vs.
11%) when compared to the average for
3000 series aluminums.
DMLS titanium (Ti-64 ELI) is most
commonly used for aerospace and
defense applications due to its
strength-to-weight ratio, temperature
resistance, and acid/corrosion
resistance. It is also used in medical
applications. Versus Ti grade 23
annealed, the mechanical properties
are nearly identical with a tensile
strength of 130 ksi, elongation at break
of 10% and hardness of 36 HRC.
Cobalt chrome (CoCr) is one of two
DMLS superalloys that tend to be
used for specialty applications in
aerospace and medical. CoCr has an
exceptional EB (20%), and it is creep
and corrosion resistant. Versus ASTM
F-75 CoCr (dependent on heat treating),
DMLS CoCr offers moderate material
properties (DMLS vs. F-75): tensile
strength of 130 ksi vs. 95-140 ksi, EB of
20% vs. 8-20%, yield strength of 75 ksi
vs. 65-81 ksi, and hardness of 25 HRC
vs. 25-35 HRC. Of all DMLS metals, CoCr
has the best biocompatibility—which
requires additional biocompatibility
Selective
Laser Sintering
SLS uses thermoplastic powders,
predominantly polyamide (PA), to
make functional parts that have greater
toughness and higher impact strength
than parts produced through SL, as well as
high HDTs (351°F to 370°F).
6 | Selecting the Right Material for Industrial 3D Printing
The tradeoffs are that SLS lacks the
surface finish and fine feature details
available with SL.
Generally, SLS PAs, when compared to
the average values of their injection-
molded counterparts, have similar
HDT values but lower values for the
mechanical properties. The exception
is the fiber-filled DuraForm HST
composite, which exceeds a mineral-
filled PA 12 in all areas except tensile
strength. In a few instances, SLS PAs
report properties that document the
degree of anisotropism.
DuraForm HST Composite is a fiber-
filled PA that is similar to a 25% mineral-
filled PA 12. The fiber content in HST
significantly increases strength, stiffness
and HDT. Compared to other SLS and
SL options (excluding ceramic-filled
materials), HST has the highest tensile
strength, flexural modulus and impact
strength, and it maintains an elevated
HDT. This makes HST a great choice
for functional applications where
temperatures exceeding 300°F may
be present. The material is somewhat
brittle, however, with an EB of 4.5%.
Also consider that like injection-
molded fiber-filled materials, there is a
significant delta in the Z-axis values.
PA 850 Black delivers ductility and
flexibility with a tensile modulus of
214 kpsi and EB of 51%, all without
sacrificing tensile strength (6.9 ksi) and
temperature resistance (HDT of 370°F).
These characteristics make PA 850 a
popular general-purpose material and
the best solution for making living
hinges for limited trials.
When compared to the averages for
injection-molded PA 11, PA 850 has
a higher HDT (370°F vs. 284°F) with
similar tensile strength and stiffness.
However, its EB, while the highest of all
AM plastics, is 60% less than that for a
molded PA 11.
Another factor that distinguishes PA 850
is its uniform, deep-black color. Black
has high contrast, which makes features
pop, and it hides dirt, grease, and
grime. Black is also desirable for optical
applications due to low reflectivity.
ALM PA 650 is a balanced, economical,
go-to material for general-purpose
7 | Selecting the Right Material for Industrial 3D Printing
The range of materials also offers
options for color and opacity. Combined
with good surface finish and high
feature resolution, SL can produce parts
that mimic injection molding in terms of
performance and appearance.
The photopolymers are hygroscopic
and UV sensitive, which may alter the
dimensions and performance of the part
over time. Exposure to moisture and UV
light will alter the appearance, size, and
mechanical properties.
Accura Xtreme White 200 is a widely
used SL material. In terms of flexibility
and strength, it falls between
polypropylene and ABS, which makes
it a good choice for snap fits, master
patterns, and demanding applications.
Xtreme is a durable SL material; it has a
very high impact strength (1.2 ft.-lb./in.)
and a high EB (20%) while mid-range in
strength and stiffness. However, its HDT
(117°F) is the lowest of the SL materials.
Compared to the average value for
injection-molded ABS, Xtreme can have
a slightly higher tensile strength (7.2 ksi
vs. 6.0 ksi) but slightly lower EB (20% vs.
30%). Under a flexing load, Xtreme is
26% less rigid, and its impact strength is
70% lower.
Somos WaterShed XC 11122 offers a
unique combination of low moisture
absorption (0.35%) and near-colorless
transparency. Secondary operations
will be required to get the material
completely clear, and it will also retain a
very light blue hue afterward.
PA 650 is stiffer than PA 850 (tensile
modulus of 247 ksi vs. 214 ksi) and has
a similar tensile strength (7.0 ksi vs. 6.9
ksi). While its EB is half that of PA 850, at
24% it’s still one of the top performers
in terms of ductility. PA 650 is loosely
comparable to the average properties
for an injectionmolded PA 12. It has
similar stiffness but roughly half the
tensile strength and EB. However, its
HDT is significantly higher: 351°F vs.
280°F.
PA 615-GS is a polyamide powder
loaded with glass spheres that make it
stiff and dimensionally stable. However,
the glass filler makes PA 615-GS brittle,
significantly decreasing impact and
tensile strengths. The glass spheres also
make PA 615-GS parts much heavier
than those made with any other AM
material.
PA 615-GS mimics the average value
of glass-filled injection molded nylons.
When compared to 33% glass-filled
nylon, the HDT is lower at 350°F vs.
490°F with a much lower tensile
strength (80%) and EB (50%).
Sterelithograpghy
SL uses photopolymers, thermoset resins
cured with ultraviolet (UV) light. It offers
the broadest material selection with a
large range of tensile strengths, tensile
and flexural moduli, and EBs. Note that the
impact strengths and HDTs are generally
much lower than those of common
injection-molded plastics.
8 | Selecting the Right Material for Industrial 3D Printing
While good for general-purpose
applications and pattern-making,
WaterShed is the best choice for flow-
visualization models, light pipes, and
lenses.
Watershed’s tensile strength and EB
are among the highest of 3D-printed,
thermoplastic-like materials, which
makes it tough and durable. Compared
to average injection-molded ABS
values, Watershed offers a slightly
higher tensile strength (7.8 ksi vs. 6.0
ksi), but falls short in EB (20% vs. 30%)
and HDT at 130°F vs. 215°F.
RenShape 7820 is another alternative
when prototyping injection-molded
ABS parts. It not only mimics ABS’s
mechanical properties, its deep black
color and glossy up-facing surfaces in
a top profile offer the appearance of
a molded part, while layer lines may
be visible in a side profile. RenShape
7820 also has low moisture absorption
so that parts are more dimensionally
stable.
Compared to other SL materials, it has
midrange values for all mechanical
properties. Compared to average ABS
values (injection molded), it has a
slightly higher tensile strength (7.4 ksi
vs. 6.0 ksi), but a lower EB (18% vs. 30%)
and HDT at 124°F vs. 215°F. The most
significant departure from ABS is a low
impact strength of 0.91 ft.-lb./in.
Accura 60 is an alternative to both
RenShape SL 7820 and WaterShed
XC 11122 when stiffness is desired.
Like RenShape SL 7820, this material
produces sharp, crisp details; like
WaterShed, the material offers
translucency. However, this material
sacrifices ductility with 29% to 36%
lower EB and 10% to 44% lower impact
strength. Additionally, Accura 60 has a
high rate of moisture absorption, which
can affect dimensional stability.
Accura 60 has a high tensile strength of
9.9 ksi and high tensile modulus of 450
ksi. Comparted to the average values
for an injection-molded, 10% glass-
filled polycarbonate, it has equivalent
tensile strength and flexural modulus,
25% higher EB but 80% lower impact
strength.
Somos 9120 is the best choice of the
SL resins when polypropylene-like
parts are needed. This material is the
most flexible SL option, with a flexural
modulus of 210 ksi, and the most
ductile, with an EB of 25%. It also has
the second highest impact strength (1.0
ft.-lb./in.) of the SL materials. In direct
comparison to the average values of
an injection-molded polypropylene,
9120 has similar tensile strength (4.7
ksi), tensile modulus (212 ksi), flexural
modulus (210 ksi), and impact strength
(1.0 ft.-lb./in.). The only departure from
molded PP is a 75% lower EB.
Accura SL 5530 provides a strong, stiff
part with high temperature resistance.
Furthermore, a thermal post-cure
option can increase HDT from 131°F to
482°F. 5530 has the highest tensile
9 | Selecting the Right Material for Industrial 3D Printing
to 29 ksi, depending on the percentage
of metal volume. HDT is drastically
increased over NanoTool with a range of
122°F up to 516°F, and when compared
to die-cast aluminum, the HDT is greater
than 500°F with a tensile strength of 43.5
ksi.
and flexural moduli (545 ksi and 527
ksi, respectively) of all the unfilled
SL materials and the second highest
tensile strength (8.9 ksi). However, the
postcure does make 5530 less durable,
resulting in an impact strength of only
0.4 ft.-lb./in. and an EB of 2.9%. Without
the thermal post-cure, 5530 retains its
tensile strength and becomes more
flexible. Also, EB increases by 50%.
When compared to injection-molded
thermoplastics, a 10% glass-filled
polycarbonate is the closest match.
With the thermal post-cure, 5530 has
similar tensile strength and flexural
modulus (compared to the average
values) with 66% higher HDT. However,
impact strength and EB are much
lower for 5530 (81% and 72% lower,
respectively).
MicroFine Green is custom formulated
at Protolabs to deliver the highest
level of detail—0.002 in. features
are possible—and tightest tolerance
available from any SL material. The
material is used to make small parts,
generally less than 1 in. by 1 in. by 1 in.
In terms of mechanical properties,
MicroFine Green falls in the mid-range
of SL materials for tensile strength
and modulus (6.5 ksi and 305 ksi,
respectively) and on the low end for
impact strength and EB (0.46 ft.-lb./in.
and 6% respectively).
MicroFine Green has a stiffness (329 ksi
vs. 333 ksi) and tensile strengths (6.5 ksi
vs. 6.0 ksi) similar to injection-molded
ABS, however, MicroFine does have a
lower HDT than ABS of 138°F vs. 215°F.
Protolabs offers another proprietary
material, SLArmor, combining nickel
plating with Somos NanoTool parts
to offer an alternative to die-cast
aluminum. The plating increases
NanoTool’s tensile strength to 14.5 ksi
Conclusion
Spanning metals, thermoplastics, and
thermosets, 3D printing provides many
different materials that can simulate, if not
replace, those that are processed through
conventional means. While an exact match
is not possible, since the fundamental
processes are different, the material
breadth means that there is a strong
likelihood that the important material
characteristics are satisfied.
The key to success is being open to, and
cognizant of, the differences. With the
support of an informed, qualified 3D
printing resource that can fill in the data
gaps, this mindset opens the door to
leveraging the unique advantages that 3D
printing technology can offer.
10 | Selecting the Right Material for Industrial 3D Printing
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