Layered Solidification Processes

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Layered Solidification Processes

• Liquid-Based Approaches
• Stereolithography
• Powder-Bed Based Approaches
• 3D Printing (Z-Corporation)
• Selective Laser Sintering

2
Stereolithography (SLA)

• First commercial layered manufacturing technology
  (1988)
• Photo-curable liquid resin
• www.3dsystems.com

3
SFF Stereolithography (SLA)

• UV laser beam solidifies the top layerof a
  photosensitive liquid.

UV Laser Beam
Photopolymer
Build Stage
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Stereolithography Principle
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Stereolithography

• Pre-process
• Orient part.
• Choose slice thickness.
• Slice parts and plan supports.

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Stereolithography

• Process
• Position build platform (stage)just below liquid
  resin surface.
• Smooth surface with re-coater blade.
• Scan the outline of the current slice, loosely
  hatch part interior with laser.
• Lower the build platform for next layer.

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Stereolithography

• Post-process
• Raise part and drain out liquid.
• (except liquid trapped by loose hatch)
• Break off supports.
• Rinse in isopropanol and water.
• Dry with air hose.
• Post-cure (strengthen) in UV oven.

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Stereolithography

• Characteristics
• Slow process
• Supports must be removed by hand
• Lab environment necessary (gasses!)
• Needs trained operator
• Laser lasts 2000hrs, costs 20000!
• Little material choice, (700 per gallon)
• Parts can be brittle, fragile

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Stereolithography

• Characteristics (cont.)
• High accuracy
• Layer thickness 0.001 - 0.006
• Minimum feature size 0.003 - 0.012
• Large build volume
• Up to 20 x 20 x 23

10
Powder-based Approaches

• Key Properties
• Needs no supports that must be removed!
• Uniform bed of powder acts as support.
• This powder gets selectively (locally) glued (or
  fused) together to create the solid portions of
  the desired part.

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SFF 3D Printing -- Principle

• Selectively deposit binder droplets onto a bed
  of powder to form locally solid parts.

Head
Powder Spreading
Printing
Powder
Feeder
Build
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3D Printing Some Key Players

• Z Corporation http//www.zcorp.com/Plaster and
  starch powders for visualization models.
• Soligen http//www.zcorp.com/Metal and ceramic
  powdersfor operational prototypes.
• Therics Inc. http//www.therics.com/Biopharmaceu
  tical products,tissue engineering.

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3D Printing Z Corporation

• The Z402 3D Printer
• Speed 1-2 vertical inches per hour
• Build Volume 8" x 10" x 8"
• Thickness 3 to 10 mils, selectable

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3D Printing Z Corporation
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3D Printing Z Corporation

• Digging out

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Optional Curing 30 min. _at_ 200ºF

• Keep some powder in place

• lt-- Tray for transport

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3D Printing Z Corporation

• Cleaning up in the de-powdering station

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3D Printing Z Corporation

• The finished part

• Zcorp,
• 6" diam.,
• 6 hrs.

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120 Cell -- Close-up
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Parallel Projection of the 4D 120-Cell

• Zcorp,
• 6" diam.,
• 6 hrs.

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Morin Surface
3D-Print6" diam. 5 hrs.

• This is the half-way point of a sphere eversion
  (without causing creases or tears).

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3D Color Printing Z Corporation

• The Z402C 3D Color Printer
• Differences compared to mono-color printer
• Color print head with Cyan, Yellow, Magenta,
  Black, and Neutral.
• Smaller build area.
• Specs
• Speed 0.33 - 0.66 vertical inches per hour
• Build Volume 6" x 6" x 6"
• Layer Thickness 3 to 10 mils, selectable
• Color depth 80 mils below surface

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3D Color Printing Z Corporation
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3D Color Printing Z Corporation

• Use compressed air to blow out central hollow
  space.

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3D Color Printing Z Corporation

• Infiltrate Alkyl Cyanoacrylane Ester
  super-glue to harden parts and to intensify
  colors.

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3D Color Printing Z Corporation

• Lizard-Frame Final Infiltrated Part

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Hypercube, Perspective Projections
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Two Ways to Make a Hypercube

• 3D Color Print

Assembly of flat FDM parts gt
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What Can Go Wrong ? -- Parts may brake before
infiltration
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What Else Can Go Wrong ?

• Blocked glue lines
• Crumbling parts

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Post-Processing for 3D-Printing

• Surface is porous, dusty.? seal and strengthen
  the part
• Dip in wax
• Nice smooth finish
• Needs separate waxing station
• Infiltrate with superglue
• Tedious, dirty manual labor
• Spray-paint with a sealant
• Polyurethane (yellowish, smelly)
• Krylon (invisible)

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Post-Processing for 3D-Printing

• Spray-paint surface with Krylon

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3D Printing Z Corporation

• An Informal Evaluation
• Fast !
• Running expenses moderate,(but overpriced
  powder)
• Color print head and tubes need some care in
  maintenance.
• Somewhat messy cleanup !
• Lots of dust everywhere ...

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Selective Laser Sintering (SLS)

• Key Points
• Powder gets solidified with a laser.
• Powder is kept just below melting point, heat
  from laser will fuse powder grains.
• Un-fused powder acts as support,can easily be
  removed later.
• Many different materials can be used when mixed
  with a suitable bindernylon, metal, ceramics

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SLS Conceptual View
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SLS Players

• 3D SYSTEMS
• Representing the fourth generation of SLS
  (selective laser sintering) technology,
  Vanguard and Vanguard HS (High Speed), are
  the first SLS systems developed specifically
  for advanced manufacturing applications.
• With the Vanguard system you can move directly
  from a CAD file to a durable, functional plastic
  or metal part or tool in a fraction of the
  time required for traditional machining and
  tooling.
• http//www.3dsystems.com/products/sls/vanguard/ind
  ex.asp

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SLS from 3D SYSTEMS

• Use Vanguard or Vanguard HS system for 
  Plastic or metal parts, patterns prototypes 
  Complex metal tooling inserts  Highly Durable
  Parts  Parts with small features  Short runs
  of plastic metal parts
• Benefits  High part accuracy   Fast build
  speed  Unattended operation  Uses plastic or
  metal materials  Respond to customer demands 
  Worldwide service and support

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SLS Laserform Parts
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The Most Challenging SFF Part

• 3rd-order 3D Hilbert Curve
• much weight
• much length
• no supports
• only two tube-connectionsbetween the two
  halves.

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Fabricated by ProMetal
41
ProMetal Process

• A green part is first formed, composed of
  stainless steel powder and a selectively applied
  binder.
• This part is built bottom-up, layer-by-layer
  under direct computer control.
• This green part is then sintered, the binder is
  drained out and replaced by liquid bronze.
• ProMetal is a division of The Ex One Company,
  Irwin, PA.

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Which Process Should You Pick?

• Do you need a prototype (not just a model)?
• ? SLS, FDM (for robustness, strength).
• Do you need a mold for a small batch?
• ? SLA (for smooth, hard surface).
• Does part need multiple colors?
• ? 3D Color-Printing.
• Does part have convoluted internal spaces?
• ? 3D-Print, SLS, SLA (easy support removal).

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Informal Process Ratings Matrix