© Bradley Jared, 2023
Principles of Additive Manufacturing
ME 469/569, Fall
Dr. Bradley Jared
Binder Jetting
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© Bradley Jared, 2023
Project #3: Crush It
• Design (due 11/7)
— Solid Works 2023 design template 20mm
• 10x15x20mm shell w/ 0.5mm wall thickness
— design desired internal structure
• fill to 50% (1500mm3)
• must be printable & able to remove powder
• NetFabb export? 15mm
— pay for as-printed part? 10mm
— submission
• upload native CAD design
• Solid Works or Fusion 360
• clearly identify print direction in text or some part feature (sketch?)
• Build on Farsoon FS271M in 316L SS
• Predict
— yield point using SW Simulation
— specify & justify selection for material yield strength
• Test
— determine yield point
• Report
— predictions & outcomes
© Bradley Jared, 2023
Logistics
• MDF tour update
• Questions?
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© Bradley Jared, 2023
Additive Manufacturing
• Metal powder bed fusion & directed energy deposition
— How to improve?
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© Bradley Jared, 2023
Binder Jetting
• ISO/ASTM 52900:2021
— binder jetting, n: AM process in which a liquid bonding agent is selectively
deposited to join powder materials
• Also includes
— sintering
— infiltration
Fig. 8.1 Schematic of
binder jetting process
Cordero, Add Mfg, 2017
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© Bradley Jared, 2023
Motivations
Fig. 8.8 casting
• Scalable mold block
— increase bed size & add printheads
— inkjet technology is robust,
inexpensive & available
• High deposition rate
— unaffected by part size, geometry or
number
— production machines ~ 12,000cm3hr
• Low cost
— no high power energy source
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© Bradley Jared, 2023
Motivations
• Complexity
— dimensional
— “multi-material” / color
• “Decent” properties
— powder + binder + infiltrant yield unique
combinations
— porosity & infiltrants weaken
— no residual stress
full color sandstone print
courtesy: Hubs
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© Bradley Jared, 2023
Applications
• Visual representations, figurines
Fig. 8.8 automobile part
& models
— prototypes Fig. 8.8 filter
• Tooling & molds
courtesy:
Zcorp
— internal cooling channels
• Investment / sand casting molds
& cores
— automotive, heavy equipment, oil &
gas
Fig. 8.6 Injection mold with
conformal cooling channels
courtesy: ExOne Company
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Fig. 8.5 Voxeljet VXC800 © Bradley Jared, 2023
History
• early 1990s: MIT development & patent
— licensed based on material & application
— Z-Corp
• starch & plaster / low-viscosity glue, concept models
• 2012: 3D Systems purchases, now ProJet
— Ex-One Zcorp Z402 HP Metal Jet
courtesy: 3DSourced
• metal, sand / polymer for sand casting
— Therics Cima, SFF, 1995
• tissue scaffolding, biomedical
• 2005: Voxeljet, German
— 2013: continuous process w/unlimited length
— sand / polymer, for models & castings
• Recent entries
— Desktop Metal (2015), HP (2016), GE (2021)
Desktop Metal alumina engine chamber, green
9 production system body (left), fully dense (right)
© Bradley Jared, 2023
Printing
• No special environment required
• Powder layers
— metal, polymer, plaster: spread dry
— ceramics: inkjet slurry Mostafaei, Prog in Mat Sci,2021
— ~10-500µm layer thickness
• Print binder courtesy:
— ~80µm dia. droplets @ kHz ExOne
• droplet formation requires <20-40cP viscosity
• Newtonian fluids
• surface tension limits droplet size & stability
• OEM proprietary formulations
— geometry controlled by droplet placement
— “green” part
• low mechanical strength & density
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courtesy: © Bradley Jared, 2023
Elnik
Systems
De-binding & Sintering
• Dwell for some binders courtesy:
3DPrintingToday
— require set to gain part strength
• Part & powder removal
• Metal / ceramic
— furnace cycles de-bind then sinter
— de-binding green vs. sintered 316L
part, courtesy: GKN
• diffusion & burn-out Hoeganaes, Zwiren
— 40-60% shrinkage
• challenges w/deformation & cracking
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© Bradley Jared, 2023
Infiltration
• Unique to binder jetting
• Porosity can exceed 60%
— infiltrant improves mechanical properties
— polymer, plaster: dip Cui, Wear,2021
• Metals & ceramics
— lower melting temperature alloy / material
— contacts parts
— infuses by capillary action when heated
— final parts >90% dense
• Then, finishing & metrology
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© Bradley Jared, 2023
Feedstock
• Powder / binder / infiltrant combinations
— polymer (ex. PMMA) / liquid / wax
• composite
— metal, ceramic / polymer / bronze, monolithic
metal
— plaster / water based / acrylate, strengthener courtesy:
ExOne
• color
— sand, silica / two-part binder, inorganic binder
• casting cores & molds
• Powder
— fully re-useable
— desire high packing density
• includes range of large & small powder
— Desktop Metal
• metal injection molding powder
courtesy:
• larger, cheaper, safer, irregular ExOne
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© Bradley Jared, 2023
Equipment
• Ambient, room temperature
environment
• Powder delivery
— hopper & spreader
• often counter-rotating roller similar to
PBF
• constant translation motion
• build plate stepdown establishes layer
thickness
— powder handling scales with
volume
• hand carry to rail cars
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© Bradley Jared, 2023
Equipment courtesy: Xaar
• Binder jetting
— slurry inkjet printheads
— commonly exceed 1000 nozzles /
head
• dedicated color, material & binder nozzles Xaar 1003 AMx printhead,
• ~100µm resolution common for AM system
— simple translation
• no start-stops or contours
• droplet timing & control
• Debinding / sintering furnace
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316L SS © Bradley Jared, 2023
microstructure
courtesy: Desktop Metal
Printed Material
courtesy: 3D
Systems
• Plaster / infiltrants
— stiffer, but weaker than thermoplastics
• Homogenous metal
— 316L, 17-4PH, 304L
— properties comparable w/metal injection molding courtesy:
Johnson Matthey
• Bronze infiltrated metal
— 316 SS, 420 SS, W
— many metals in development
• Ceramics courtesy: ExOne
— silicon carbide, boron carbide, alumina, zirconia,
silica, titanium dioxide
• Sand
— binder improves mechanical properties after
curing courtesy:
ExOne
Cui,
16 Wear,2021
© Bradley Jared, 2023
Design Constraints Fig. 8.7 ExOne S-Max
system
• Size
— 1” to many yards
• Resolution
— powder & inkjet droplet
— green state feature strength
• Finish
— similar to PBF ~ powder diameter
courtesy: Hubs
SS oil & gas stator infiltrated w/bronze
courtesy: ExOne
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© Bradley Jared, 2023
Design Constraints
• Accuracy
— ExOne metal: ±0.125mm
— ~40-60% shrinkage & distortion for courtesy: Additive
metal & ceramics Manufacturing Media
— developing simulation capabilities to
predict & compensate
• No support structures
— parts stacked in build volume
— metal: supports can reduce
distortions
• Reduced properties
— residual porosity
— infiltrant materials
courtesy: Hubs
SS oil & gas stator infiltrated w/bronze
courtesy: ExOne
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© Bradley Jared, 2023
Homework: Read AMT Ch. 8, Project #3
Questions?
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