manufacturing metallic parts with designed mesostructure via three-dimensional printing of metal...

Manufacturing Metallic Parts with Designed Mesostructure

via

Three-Dimensional Printing of Metal Oxide Powder

August 08, 2007

Christopher B. Williams

David W. Rosen


David W. RosenWoodruff School of Mechanical Engineering

Georgia Institute of TechnologyAtlanta, Georgia

Systems Realization Laboratoryhttp://www.srl.gatech.edu

Rapid Prototyping and Manufacturing Institutehttp://www.rpmi.marc.gatech.edu

August 08, 2007

Manufacturing Metallic Parts with Designed Mesostructure

via

Three-Dimensional Printing of Metal Oxide Powder


David W. Rosen


David W. RosenWoodruff School of Mechanical Engineering

Georgia Institute of TechnologyAtlanta, Georgia

Systems Realization Laboratoryhttp://www.srl.gatech.edu

Rapid Prototyping and Manufacturing Institutehttp://www.rpmi.marc.gatech.edu

Parts of Designed Mesostructure:• What are they?• Why are they of interest?• How are they manufactured?• What are the limitations of current manufacturing processes?• What are potential areas for improvement?

Parts of Designed Mesostructure:• What are they?• Why are they of interest?• How are they manufactured?• What are the limitations of current manufacturing processes?• What are potential areas for improvement?

• What is our answer? – 3DP of metal-oxide ceramic green part followed by post-

processing in a reducing atmosphere

• Why 3DP of metal-oxide powders?• Preliminary results - characteristic cellular material geometry:

– Thin walls– Angled trusses– Small channels

• What is our answer? – 3DP of metal-oxide ceramic green part followed by post-

processing in a reducing atmosphere

• Why 3DP of metal-oxide powders?• Preliminary results - characteristic cellular material geometry:

– Thin walls– Angled trusses– Small channels

3

Georgia Institute of TechnologySystems Realization Laboratory

Low-Density Cellular Materials

Benefits:Benefits:

Metallic Foams Lattice Block Material Linear Cellular Alloys

• Strain isolation• Energy absorption• Excellent heat transfer

ability

• High strength• Low mass• High stiffness• Acoustic & vibration

dampening

© Christopher B. Williams

4


Cellular Material Applications: Designed Mesostructure

(V. Wang, 2004)

(C. Seepersad, 2005)

(V. Wang, 2006)

(H. Muchnick, 2007)

(Fleck & Deshpande, 2004)

Combustor Liner

Robot Arm

Acetabular Cup

Blast Resistant Panel

5


Cellular Material ManufacturingStochastic Cellular Material Manufacturing (Hydro / Alcan / Combal Process)

Ordered Cellular Material Manufacturing (Honeycomb via Crimping & Stamping)

Existing cellular material manufacturing techniques are severely limited:1. Part Macrostructure2. Materials

Existing cellular material manufacturing techniques are severely limited:1. Part Macrostructure2. Materials

3. Non-repeatable results4. Limited mesostructure topology

Williams, C. B., F. M. Mistree, D. W. Rosen, 2005, “Investigation of Additive Manufacturing Processes for the Manufacture of Parts with Designed Mesostructure,” ASME IDETC, DETC2005/DFMLC-84832

6


Direct Metal Additive Manufacturing

Laser Engineered Net Shaping

Electron Beam Melting

Williams, C. B., F. M. Mistree, D. W. Rosen, 2005, “Investigation of Additive Manufacturing Processes for the Manufacture of Parts with Designed Mesostructure,” ASME IDETC, DETC2005/DFMLC-84832

Resol

utio

nM

ater

ial

Surfa

ce

Suppo

rt

Prope

rtiesLimitations

(wrt cellular materials)

Pro

cess

es

Recoa

tPat

tern

SLS

DMLS

SLM

EBM

3DP

MJS

EDSSM

LENS

SDM

UOC

LOM

CAM-LEM

x x x x x xx x x x x

x x x xx x x x x

x x x xx x x x x x

x x x x x xxx xx

x xxx x x x

x x x x

x x x x x

x

7


Direct Metal Additive Manufacturing




Direct Metal Laser SinteringDirect Metal

Laser Sintering Selective Laser Melting

Selective Laser Melting

http://www.mcp-group.com/rpt/rpttslm_1.html

8


Spray-Drying

Finished Metal Part

OxidePowders

Compounding

Additives

Step OnePaste Preparation

H2

Direct Reduction

Step ThreeDirect Reduction

Drying

Honeycomb Extrusion

Finished Metal Part

OxidePowders

Spraying

Additives


H2

Direct Reduction


Drying

Finished Metal PartFinished Metal PartFinished Metal Part

OxidePowders Additives


OxidePowders Binder

Step OneSpray Drying

H2


H2


H2


Step TwoAdditive Manufacturing via 3DP

3DP of Metal Oxide Powder + Sintering in Reducing Atmosphere


9


Finished Metal Part

OxidePowders

H2O

Compounding

Additives


H2

Direct Reduction


Drying

Honeycomb Extrusion

Step TwoShape Fabrication

Flexible Die Design

Finished Metal Part

OxidePowders

H2O

Compounding

Additives


H2

Direct Reduction


Drying

Honeycomb Extrusion


Flexible Die Design


OxidePowders

H2O

Compounding

Additives


OxidePowders

H2OH2O

Compounding

Additives


H2

Direct Reduction


Drying

H2

Direct Reduction


H2

Direct Reduction


DryingDrying

Honeycomb Extrusion


Flexible Die Design

Honeycomb Extrusion


Honeycomb Extrusion


Flexible Die Design

Reduction & Sintering of Metal Oxides

J. Cochran, T. Sanders, D. McDowell - GT Lightweight Structures Group

3 4 2 2Fe O + 4H 3Fe + 4H O

3 4 2 2Co O + 4H 3Co + 4H O

2 2NiO + H Ni + H O

Maraging Steel: Fe 18.5Ni 8.5Co 5Mo


10



• Materials:– Fe, Cu, Co, Cr, Ni, Mo, W, etc.– Maraging / Stainless steel, Iconel, Super Invar– No Al or Ti

• Cost effective:– Metal oxides 10x cheaper than metal counterpart

• Safe:– Non-carcinogenic– Chemically stable

• Geometric considerations:– Need open access to interior– Minimize thickness variation– Large shrinkage upon processing

• Materials:– Fe, Cu, Co, Cr, Ni, Mo, W, etc.– Maraging / Stainless steel, Iconel, Super Invar– No Al or Ti

• Cost effective:– Metal oxides 10x cheaper than metal counterpart

• Safe:– Non-carcinogenic– Chemically stable

• Geometric considerations:– Need open access to interior– Minimize thickness variation– Large shrinkage upon processing


11


Finished Metal Part

OxidePowders

H2O

Compounding

Additives


H2

Direct Reduction


Drying

Honeycomb Extrusion


Flexible Die Design

Finished Metal Part

OxidePowders

H2O

Compounding

Additives


H2

Direct Reduction


Drying

Honeycomb Extrusion


Flexible Die Design


OxidePowders

H2O

Compounding

Additives


OxidePowders

H2OH2O

Compounding

Additives


H2

Direct Reduction


Drying

H2

Direct Reduction


H2

Direct Reduction


DryingDrying

Honeycomb Extrusion


Flexible Die Design

Honeycomb Extrusion


Honeycomb Extrusion


Flexible Die Design

Step TwoAdditive Manufacturing

Store material

Pattern

Provide energy

Provide new material

Provide support

Create Patterning

Control

Slice CAD file into layers

Post-Process Part

CAD file

data

materials

energy

signals

system boundary

Legend

materials

energy

signals

system boundary

Legend



?


12


Design of an Additive Manufacturing Process

Design Task: • To design an AM process for the realization of metal-oxide ceramic green

cellular parts suitable for post-processing in a reducing atmosphere• Specific requirements of cellular materials:

– Features 250 m – Multiple materials

Design Task: • To design an AM process for the realization of metal-oxide ceramic green

cellular parts suitable for post-processing in a reducing atmosphere• Specific requirements of cellular materials:

– Features 250 m – Multiple materials

– Cell sizes of 0.5 – 2 mm– Comparable speed and cost


13


Design and Development of an Additive Manufacturing ProcessClarification of Task

D / W Requirement Geometry D Able to process any macrostructure geometry D Able to process complex geometry (overhangs

and internal voids) D Able to process small cell sizes (0.5 – 2 mm) D Build small wall thickness (50 – 300 m) W Minimize amount of effort required to adapt to a

new material Material D Able to process multiple materials (steel, iron,

aluminum, copper, etc.) W Able to process standard working material Production W Maximize deposition rate (> 10 cm3/hr) D Build envelope is 305 x 305 x 305 mm or larger W Does not require additional post-processing Quality Control D Parts are > 98% dense D Material properties are comparable to standard D Minimize surface roughness before finishing (<

0.02 mm Ra) D Maximize accuracy (> +/- 0.05 mm) D Minimize z-resolution (< 0.1 mm) Operation W Does not require special operating environment W Minimize operator interaction Recycling D Minimize environmental impact by minimizing

wasted material W Reusable wasted material Costs D Minimize cost of technology D Minimize cost of maintenance W Minimize cost of material D Easily scaled for large applications

Requirements List

Conceptual Design

Both

(2D)

Energy

(2D)

Material

(2D)

Both

(1D)

Energy

(1D)

Material

(1D)Pattern

Solutions

Direct Material Addition

Recoat by Layer

Recoat by Dipping

Recoat by Spraying

Recoat by Spreading

Provide New

Material

No SupportOrganic Support Material

Dissolvable Support Material

Thin Trusses of Build Material

Breakable Support Material

Material Bed

5-axis Deposition

Support

Chem. Reaction

CutBindCladMeltSinterProvide Energy

Tape / SheetGasWire / RodPowder / Binder

Suspension

Powder Coated w/

Binder

Two Phase Powder

PowderStore

Material

Both

(2D)

Energy

(2D)

Material

(2D)

Both

(1D)

Energy

(1D)

Material

(1D)Pattern

Solutions

Direct Material Addition

Recoat by Layer

Recoat by Dipping

Recoat by Spraying

Recoat by Spreading

Provide New

Material

No SupportOrganic Support Material

Dissolvable Support Material

Thin Trusses of Build Material

Breakable Support Material

Material Bed

5-axis Deposition

Support

Chem. Reaction

CutBindCladMeltSinterProvide Energy

Tape / SheetGasWire / RodPowder / Binder

Suspension

Powder Coated w/

Binder

Two Phase Powder

PowderStore

Material

Sub

-Fun

ctio

ns

SLS SLA MJS EFF 3DP IJP-a IJP-w EP LOMECONOMICSTechnology Cost 0 0 1 1 1 1 1 1 1Score 0 0 1 1 1 1 1 1 1Normalized Score 0.00 0.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00TIMEDeposition rate 1 0 -1 -1 -1 -1 1 1 1Score 1 0 -1 -1 -1 -1 1 1 1Normalized Score 1.00 0.50 0.00 0.00 0.00 0.00 1.00 1.00 1.00PERFORMANCEmin. feature size -1 0 -1 -1 -1 -1 -1 -1 -1complex geometry 0 0 1 1 0 1 1 1 -1surface finish -1 0 -1 -1 -1 0 0 -1 -1Score -2 0 -1 -1 -2 0 0 -1 -3Normalized Score 0.33 1.00 0.67 0.67 0.33 1.00 1.00 0.67 0.00MATERIALSSolids Loading -1 0 0 0 1 1 -1 0 1Material properties -1 0 -1 -1 1 1 0 -1 -1Material selection 1 0 1 1 1 1 1 1 1Score -1 0 0 0 3 3 0 0 1Normalized Score 0.00 0.25 0.25 0.25 1.00 1.00 0.25 0.25 0.50

Morphological Matrix &

Preliminary Selection Decision Support Problem

Embodiment Design

Three Dimensional PrintingWilliams, C. B., F. M. Mistree, D. W. Rosen, 2005, “Towards the Design of a Layer-Based

Additive Manufacturing Process for the Realization of Metal Parts of Designed Mesostructure,” Solid Freeform Fabrication Symposium, pp. 217-230.

14


Three Dimensional Printing

• ~100 m feature size

• Two-dimensional deposition

• Cost effective, scalable technology

• 50% solids loading in green part

• ~100 m feature size

• Two-dimensional deposition

• Cost effective, scalable technology

• 50% solids loading in green part

• Unable to spread fine particle sizes

• Powder bed leads to trapped unbound powder


15


Spray Drying

Spray-dried powder

• Fine particles (1-5 m) in granule form (30-50 m)

• Spherical and flowable• Smaller primitives• Modular binder/powder

combo

Spray-dried powder

• Fine particles (1-5 m) in granule form (30-50 m)

• Spherical and flowable• Smaller primitives• Modular binder/powder

combo

Drying Air

Exhaust

Granules

Powder / Binder Suspension


16


Spray-Drying

Finished Metal Part

OxidePowders

Compounding

Additives


H2

Direct Reduction


Drying

Honeycomb Extrusion

Finished Metal Part

OxidePowders

Spraying

Additives


H2

Direct Reduction


Drying


OxidePowders Additives


OxidePowders Binder

Step OneSpray Drying

H2


H2


H2


Step TwoAdditive Manufacturing via 3DP

3DP of Metal Oxide Powder + Sintering in Reducing Atmosphere

Maraging Steel Oxide

Powder

PVA:2 wt%4 wt%

ZCorp Z402 printer

• ZB7 binder

• Layer thickness: 100 m

• Core saturation: 1.75

0

200

400

600

800

1000

1200

1400

0.00 3.54 4.04 6.26 14.26 16.76 19.76 24.01

Time (hr)

Te

mp

era

ture

(C

)

Sintering1350 C

Reduction850 C

Binder burnout450 C


17


General Results

• Fragile green parts• Linear shrinkage: 46%• Relative density: 65.3%• Internal open porosity: 29.8%

• Fragile green parts• Linear shrinkage: 46%• Relative density: 65.3%• Internal open porosity: 29.8%


18


Thin Wall Test

• 400 m thin wall (sintered)• Dependent on dpi of 3DP

machine

• 400 m thin wall (sintered)• Dependent on dpi of 3DP

machine


19


Channel Test

• 2 mm x 2 mm x 10 mm open channels• 500 m channels have been

successfully printed• Channel size limited by powder removal

• 2 mm x 2 mm x 10 mm open channels• 500 m channels have been

successfully printed• Channel size limited by powder removal


(C. Seepersad, 2005)

20


Angled Truss Test

L

x

y

LT

t

sin tan

t LTx

sin tan

t LTx

(V. Wang, 2004)


21


Angled Truss Test

• 2 mm diameter truss (1.08 mm sintered)• 45o angle• 0.328 mm layer overlap• 2 mm wall / truss gap (green)

• 2 mm diameter truss (1.08 mm sintered)• 45o angle• 0.328 mm layer overlap• 2 mm wall / truss gap (green)


22


Angled Truss Test


23


Angled Truss Test


24


Spray Dried Powder Results

Granule binder content

Deposited binder

Relative density

Open porosity

2 wt% ZB7 65.3% 29.8%

4 wt% ZB7 59.2% 36.4%

4 wt% Solvent 64.3% 33.4%


25


Summary: Critical Analysis

• Scalable technology (parallel deposition)• Cost-effective (technology and material)• Modular binder / material combination• Able to process several materials and alloys• Successfully fabricated 400 m walls, angled trusses,

small channels

• Scalable technology (parallel deposition)• Cost-effective (technology and material)• Modular binder / material combination• Able to process several materials and alloys• Successfully fabricated 400 m walls, angled trusses,

small channels

• Low sintered density• Poor surface finish• Fragile green part; difficult to de-powder• Cannot process Ti or Al• Cannot produce powder-filled cells

• Low sintered density• Poor surface finish• Fragile green part; difficult to de-powder• Cannot process Ti or Al• Cannot produce powder-filled cells


26


Next Steps…

• Materials Characterization– XRD phase analysis– Tensile and bending tests

• Primitive formulation modeling

• Alternatives for further densification of green part

• Materials Characterization– XRD phase analysis– Tensile and bending tests

• Primitive formulation modeling

• Alternatives for further densification of green part


27


Acknowledgements

• NSF DMI-0522382

• NSF IGERT - 0221600

• Mr. Joe Pechin, Aero-Instant Spray Drying Services

• Dr. Joe Cochran, Georgia Tech, Materials Science and Engineering Department

• Michael Middlemas & Tammy McCoy

• Dr. Scott Johnston & Ben Utela

• Dr. Carolyn Seepersad

• NSF DMI-0522382

• NSF IGERT - 0221600

• Mr. Joe Pechin, Aero-Instant Spray Drying Services

• Dr. Joe Cochran, Georgia Tech, Materials Science and Engineering Department

• Michael Middlemas & Tammy McCoy

• Dr. Scott Johnston & Ben Utela

• Dr. Carolyn Seepersad


Thank you.

NSF Grant DMI-0085136

NSF IGERT-0221600

NSF Grant DMI-0522382

29


Supplemental Slides

30


Classification of Cellular Materials

LOW-DENSITY CELLULAR MATERIALS

Parts of Designed Mesostructure

• a class of cellular structures wherein material is strategically placed by a designer in order to achieve certain design objectives (i.e., low mass, high strength, high stiffness, etc.)

• Pertains to a group of manufacturing processes that provide a designer the freedom to prescribe mesostructure topology for a design’s intent

Parts of Designed Mesostructure

• a class of cellular structures wherein material is strategically placed by a designer in order to achieve certain design objectives (i.e., low mass, high strength, high stiffness, etc.)

• Pertains to a group of manufacturing processes that provide a designer the freedom to prescribe mesostructure topology for a design’s intent

Stochastic

• (Solid) metal foams

• Metal sponges

• Porous metals

• Hollow sphere foams

OrderedDesigned Mesostructure

• Linear Cellular Alloys

• Truss Structures (via Additive Manufacturing)

Periodic

• Honeycomb (via crimping/stamping)

• Lattice Block Materials

(Mesostructure: 100m – 10mm)


31


Addressing the Gap: Manufacturing Parts of Designed Mesostructure

Primary Research Question:

How to manufacture three-dimensional, low-density, cellular metal structures while maintaining designer freedom in the selection of the material and the design of the part mesostructure and macrostructure?

Primary Research Question:

How to manufacture three-dimensional, low-density, cellular metal structures while maintaining designer freedom in the selection of the material and the design of the part mesostructure and macrostructure?It is proposed to design, embody, and analyze a

manufacturing process that is capable of producing metallic cellular materials and providing a designer the freedom to specify material type, material composition, void morphology, and mesostructure topology for any conceivable part geometry.

It is proposed to design, embody, and analyze a manufacturing process that is capable of producing metallic cellular materials and providing a designer the freedom to specify material type, material composition, void morphology, and mesostructure topology for any conceivable part geometry.

32


Finished Metal Part

OxidePowders

H2O

Compounding

Additives


H2

Direct Reduction


Drying

Honeycomb Extrusion


Flexible Die Design

Finished Metal Part

OxidePowders

H2O

Compounding

Additives


H2

Direct Reduction


Drying

Honeycomb Extrusion


Flexible Die Design


OxidePowders

H2O

Compounding

Additives


OxidePowders

H2OH2O

Compounding

Additives


H2

Direct Reduction


Drying

H2

Direct Reduction


H2

Direct Reduction


DryingDrying

Honeycomb Extrusion


Flexible Die Design

Honeycomb Extrusion


Honeycomb Extrusion


Flexible Die Design

Step TwoAdditive Manufacturing

Store material

Pattern

Provide energy

Provide new material

Provide support

Create Patterning

Control

Slice CAD file into layers

Post-Process Part

CAD file

data

materials

energy

signals

system boundary

Legend

materials

energy

signals

system boundary

Legend

Research Hypothesis


3 4 2 2Fe O + 4H 3Fe + 4H O

3 4 2 2Co O + 4H 3Co + 4H O

2 2NiO + H Ni + H O

Maraging Steel: Fe 18.5Ni 8.5Co 5Mo

?Primary Research Hypothesis: Three-dimensional, low-density cellular metal structures of

any macrostructure, mesostructure, or material can be manufactured via layer-based additive manufacturing of metal-oxide ceramics followed by post-processing in a reducing atmosphere.

Primary Research Hypothesis: Three-dimensional, low-density cellular metal structures of

any macrostructure, mesostructure, or material can be manufactured via layer-based additive manufacturing of metal-oxide ceramics followed by post-processing in a reducing atmosphere.

33


Linear Cellular Honeycombs(via extrusion & reduction)

• Metal-oxide paste is extruded through die and reduced to a metal part• Metal-oxide paste is extruded through die and reduced to a metal part

Finished Metal Part

OxidePowders

H2O

Compounding

Additives


H2

Direct Reduction


Drying

Honeycomb Extrusion


Flexible Die Design

Finished Metal Part

OxidePowders

H2O

Compounding

Additives


H2

Direct Reduction


Drying

Honeycomb Extrusion


Flexible Die Design


OxidePowders

H2O

Compounding

Additives


OxidePowders

H2OH2O

Compounding

Additives


H2

Direct Reduction


Drying

H2

Direct Reduction


H2

Direct Reduction


DryingDrying

Honeycomb Extrusion


Flexible Die Design

Honeycomb Extrusion


Honeycomb Extrusion


Flexible Die Design

• Can process many different materials• Parts have excellent material properties• Oxide powders are cheaper & safer• Predictable, repeatable results• Interchangeable dies can be designed for specific design intent• Cells across cross-section need not be periodic• Excellent for multi-functional design (structural heat-exchangers)• Limited to linear extrusions

Co

chra

n,

McD

ow

ell,

et

al.

34


Metal via Reduction of Metal Oxides

• Decouples cell geometry and material composition

• Processed Fe, Ni, Co, Cr, N Cu, Mo, W, Mn, and Nb

• Allows for complex cell shape, precise cell alignment, and thin wall thicknesses (> 50 m)

• Oxide particles are cheaper, safer, purer, and more stable than metal counterparts

• No other method can compare to its material selection or mechanical properties

• Decouples cell geometry and material composition

• Processed Fe, Ni, Co, Cr, N Cu, Mo, W, Mn, and Nb

• Allows for complex cell shape, precise cell alignment, and thin wall thicknesses (> 50 m)

• Oxide particles are cheaper, safer, purer, and more stable than metal counterparts

• No other method can compare to its material selection or mechanical properties

• Paste rheology can limit freedom

• Debinding can lead to cracking and laminations

• Shrinkage can cause warpage and dimensional instability

• Material must be reducible at T < Tmelt (Al and Ti are difficult to introduce)

• Structure must have high surface-to-volume ratio and open access to interior to survive reduction process; constant web-thickness is preferable

• Mechanical properties dependent on porosity

• Creates only linear structures

• Paste rheology can limit freedom

• Debinding can lead to cracking and laminations

• Shrinkage can cause warpage and dimensional instability

• Material must be reducible at T < Tmelt (Al and Ti are difficult to introduce)

• Structure must have high surface-to-volume ratio and open access to interior to survive reduction process; constant web-thickness is preferable

• Mechanical properties dependent on porosity

• Creates only linear structures

Finished Metal Part

OxidePowders

H2O

Compounding

Additives


H2

Direct Reduction


Drying

Honeycomb Extrusion


Flexible Die Design

Finished Metal Part

OxidePowders

H2O

Compounding

Additives


H2

Direct Reduction


Drying

Honeycomb Extrusion


Flexible Die Design


OxidePowders

H2O

Compounding

Additives


OxidePowders

H2OH2O

Compounding

Additives


H2

Direct Reduction


Drying

H2

Direct Reduction


H2

Direct Reduction


DryingDrying

Honeycomb Extrusion


Flexible Die Design

Honeycomb Extrusion


Honeycomb Extrusion


Flexible Die Design

35


Why Reduction of Metal Oxides?

• Metal Oxide Powders vs. Metal Powders• Cheaper

• Safer

• Purer

• Slurry• Heat Affected Zones

• Recoating

• Shrinkage

• Material properties

• Multiple materials

Note: process can only be used for geometry with constant cross-section

• Metal Oxide Powders vs. Metal Powders• Cheaper

• Safer

• Purer

• Slurry• Heat Affected Zones

• Recoating

• Shrinkage

• Material properties

• Multiple materials

Note: process can only be used for geometry with constant cross-section

36


Principal Solution Selection: Fused Deposition Modeling

AnalysisAugmentationConceptual Design Selection

Williams, C. B., F. M. Mistree, D. W. Rosen, 2005, “Towards the Design of a Layer-Based Additive Manufacturing Process for the Realization of Metal Parts of Designed Mesostructure,” Solid Freeform Fabrication Symposium, pp. 217-230.

Le

wis

et

al.,

20

03

4 Roads

Subperimeter Voids

Agarwala et al., 1996

37


Principal Solution Selection: Stereolithography


resin surface

Difference in index of refraction (n) dominates cure depth

Difference in index of refraction (n) dominates cure depth

nresin = 1.5 nalumina = 1.44nTiO2 = 2.5 nFe2O3 = 2.5Cd

UV light source

2

2

2ln

3o o

dc

n EdC

Q n E

Where:• d = particle size,• Q = scattering efficiency; • S = particle spacing, = wavelength• Eo = Exposure given• Ec = Critical exposure of resin

SQ

Griffin & Halloran, 1995

38


Principal Solution Selection: Direct Inkjet Printing

n

o

max

1

1Re

We1/ 2 10

Seerden, Reis, Evans, Grant, Halloran, Derby, 2001

0 vol% 2 vol% 5 vol% 10 vol%

Re D0V0

We D0V02


39


http://www.niroinc.com/images/chem/spray_dryer_typen.jpg

40


Closure


manufacturing metallic parts with designed mesostructure via three-dimensional printing of metal...

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