Binder Jetting: a liquid bonding agent is selectively deposited to join
powder materials
• It can be considered as hybrid between PBF and MJ
• It was originally known as three-dimensional printing (3DP)
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• Developed in 1989 at MIT by Emanuel Sachs with patent granted in
1993
• Binder Jetting was originally known as three-dimensional printing (3DP)
• After that, several companies licensed the technology from MIT,
including ExOne, Voxeljet, and Z Corp (purchased by 3D Systems in
2011)
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Steps involved in binder jetting:
1) Powder material is spread over the build platform using a roller.
2) The print head deposits the binder adhesive on top of the powder
where required.
3) The build platform is lowered by the model’s layer thickness.
4) Another layer of powder is spread over the previous layer. The object
is formed where the powder is bound to the liquid.
5) Unbound powder remains in position surrounding the object.
6) The process is repeated until the entire object has been made
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https://youtu.be/deA-7b3guT4?si=RGeYT5RKiBu77YJV&t=100
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• After printing, the part is sometimes left in the powder bed for the
binder to fully set
• Post-processing involves removing the part from the powder bed,
removing unbound powder via pressurized air
• In some cases, and infiltration step is included to make the part
stronger
• A desirable characteristic of powders is a high packing density so that
printed parts have a high-volume fraction of powder
• High packing densities can be achieved by tailoring powder particle
shape or by including a range of particle sizes so that small particles fill
in gaps between larger particles
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Comparison to PBF:
• Similarities:
• Can utilize a wide range of polymer, composite, metal, and ceramic
materials
• Uses similar powder handling and recoating systems (same counter-
rotating rolling mechanism)
• Like SLS, it does not require the use of support structures and parts
can be arrayed in one layer and stacked
• Differences:
• Bonding occurs at room temperature >> dimensional distortions
due to thermal effects are not a problem
• It involves additional post-processing to increase strength
• It can be used to print materials with high melting temperatures
like sand
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Comparison to material Jetting:
• Similarities:
• They both feature an array of parallel nozzles for rapid patterning
• Same mechanism for droplet formation and deposition
• high deposition speed at a relatively low cost (due to the lack of a
high-powered energy source)
• Differences:
• In binder jetting, only a small portion of the part material is
delivered through the print head.
• Most of the part material is comprised of powder in the powder
bed
• Binder jetting offers more material versatility
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Plaster:
• Plaster material (calcium sulfate hemihydrate) is used by 3D systems
(previously Z-corp) with water-based binder (colored or monochrome)
• Printed parts are considerably weak, so they are typically infiltrated with
another material.
• 3D Systems provides three infiltrants:
• ColorBond: acrylate-based infiltrant similar to superglue
• StrengthMax: two-part epoxy Infiltrant used on functional parts
where very high strength is desired
• Salt Water Cure: an eco-friendly and hazard-free infiltrant
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Plaster: Zprinter 450
https://youtu.be/VBK_4ruKC8s?si=pEKyUcjsz0lhPqxj 9
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PMMA:
• PMMA (poly-methyl methacrylate) is a thermoplastic powder used by
Voxeljet, it uses a liquid binder that reacts at room temperature
• Used to make investment casting patterns, where wax-based binder is
used with PMMA to create patterns with excellent pattern burnout.
• Parts can be infiltrated with epoxy resin to add strength for functional
parts
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Thermoplastics: investment casting with PMMA 3D printed pattern
https://youtu.be/UJvjIB0rAUs?si=cqB3o3hxAuW90ccg
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Metals:
• ExOne markets machines that use metal powders for functional parts
• They use stainless steel materials and several other metals (e.g. Inconels
and tool steels) with polymer binder to make the green part
• After fabrication, the green part is put in a furnace at low temperature
to burn off the polymer binder
• Next, the part is infiltrated by placing it in the furnace in contact with
bronze (or other lower melting temperature alloy)
• This results in parts with densities greater than 90%
• In some cases, the infiltration step is skipped, and the part is sintered to
near-full density
• However, this results in higher shrinkage which needs to be
compensated for during the design stage
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Metals: metal printing using ExOne machine with bronze infiltration
https://youtu.be/ZqI0B0V-ttw?si=i_ZJi8ebS7c-FW82 13
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Sand :
• Both ExOne and Voxeljet market machines that use sand for the
fabrication of molds and cores for sand casting
• ExOne offers a silica sand and two-part binders
• One part (binder catalyst) is coated on a layer and the second part is
printed onto the layer,
• Causing a polymerization reaction to occur and binding sand
particles together
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Sand :
https://youtu.be/LFGnjkoeDng?si=9LMLVtJfXIh_2dYl
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Wood:
• Forust was founded Digital Metal company in 2021 to 3D print parts
from wood powder and sap binder
• The powder raw material is gathered from lumber and paper
manufacturing waste byproducts
• Used to sustainably manufacture custom wood products, such as
furniture, household objects, and architectural pieces
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Wood:
https://youtu.be/hrtHt_n8hP8?si=4Lcy_gbL4WMRMzDu
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Z Corp (3D systems):
• Z Corp was purchased by 3D Systems in 2012
• Printers are now branded as the ProJet X60 line of printers
• With the smallest being the ProJet 160 and largest is the ProJet
860Pro
• Mostly used to fabricate Plaster-based material (calcium sulfate
hemihydrate)
ProJet X60 line 18
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ExOne:
• ExOne markets machines that build in metal powder for functional parts
as well as silica sand for sand casting applications
• Founded in 2005 as spin-off of Extrude Hone Corp
• Machines include S-Max which is used for sand powder and M-Flex is
for metal printing
S-Max M-flex 19
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ExOne: S-Max Flex Robotic Sand 3D Printer
https://youtu.be/x0QgarYot7M?si=cpqcp3r8XYAntb1b
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Voxeljet:
• Voxeljet is a German company that markets machines that use PMMA
and sand powders
• They are used for concept models, functional models, investment
casting patterns, and sand casting applications
• Machines include VX4000, the world's biggest industrial 3D printing
system for sand molds. It has a build space 4 x 2 x 1 m (LxWxH).
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Voxeljet:
https://youtu.be/2Kd7rmPrF_w?si=nXaGHPOy01xX16vL
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• Continuous printing of parts that are larger than the AM machine
• Two different approaches have been demonstrated for continuous
printing of parts
• Linear translation
• Spiral growth
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Continuous printing via linear transition:
• Voxeljet introduced continuous linear translation printer VXC800 in 2013
• The build surface of the powder bed is inclined at a 30° angle, less than the
powder’s critical angle of repose
• Powder recoating and binder jetting are performed on this inclined build
surface
• The powder bed translates on a conveyor belt from the front to the back of
the machine >> Parts printed can be much longer than the machine
VXC800 25
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Continuous printing via linear transition:
https://trends.directindustry.com/project-15743.html
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Advantages:
• No heat applied >> more material versatility than PBF (e.g. sand)
• Material can be recycled
• Doesn’t require support structure
• Large build size
Disadvantages:
• Reduced surface finish compared to MJ
• Intensive post-processing
• Poor mechanical properties and high porosity (for uninfiltrated &
unsintered parts)
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