Two Ways for Fabrication:Subtractive manufacturing Additive Manufacturing

Rapid Prototyping • Some other names:

– Additive manufacturing– Computer controlled moldless additive manufacturing

• Part is produced by producing multiple “slices” i.e. cross sections

• From 3D model [STL file (see next slide)] to physical object, with a “click”

– Layered manufacturing– Rapid prototyping:

• Variety of methods: more and more functional products rather than just prototypes

STL File*• The STL (stereo lithography) file format is supported by many

other software packages; it is widely used for rapid prototyping and computer-aided manufacturing (CAM). STL files describe only the surface geometry of a three dimensional object without any representation of color, texture or other common CAD model attributes.

*An STL file describes a raw unstructured triangulated surface by the unit normal and vertices (ordered by the right-hand rule) of the triangles using a three-dimensional Cartesian coordinate system.

Basic Principles of Rapid PrototypingRapid Prototyping

• 3d model generated• Sliced • Each slice manufactured and layers are fused together• A voxel (volumetric pixel or, more correctly, Volumetric Picture

Element) is a volume element, representing a value on a regular grid in three dimensional space. This is analogous to a pixel, which represents 2D image data in a bitmap (which is sometimes referred to as a pixmap).

Materials For Rapid Prototyping

• Materials covered:– Thermoplastics (FDM, SLS)– Thermosets (SLA)– Powder based composites (3D

printing)– Metals (EBM, SLS) – Sealant tapes (LOM)Stereolitography (SLA)

Selective Laser Sintering (SLS)Fused Deposition Modeling (FDM)Laminated Object Modeling (LOM) 3D Printing Electron Beam Melting (EBM)

Examples of Rapid Prototyping

Applications: • Prototyping (90 %)– Concept models– Architectural models– Disney characters– Movies—or is that

real and thus manufactured?

– Etc

• Manufacturing (10%)– Implants and custom

medical devices– Aerospace parts– Pilot scale

production of lab equipment

– Molds .. A Stradivarius ?

Rapid Prototyping by Industry Sectors:

Methods for RP• Stereolitography (SLA) • Selective Laser Sintering (SLS)• Fused Deposition Modeling (FDM)• Laminated Object Modeling (LOM) • 3D Printing • Electron Beam Melting (EBM)

Selection of Optimal Process

• Functional parts:– FDM (ABS and nylon)– SLS (thermoplastics, metals)– EBM (high strength alloys, Ti, stainless steel,

CoCr)• Non functional parts:

– SLA: smoothest surface, good for casting– LOM, 3D Printing, marketing and concept

protos.

Rapid Prototyping Techniques:Machine Cost Response Time

Material Application

Fused Deposition Modeler 1600 (FDM)

$10/hr 2 weeks ABS or Casting Wax

Strong Parts Casting Patterns

Laminated Object Manufacturing (LOM)

$18/hr 1 week Paper (wood-like)

Larger Parts Concept Models

Sanders Model Maker 2 (Jet)

$3.30/hr 5 weeks Wax Casting Pattern

Selective Laser Sintering 2000 (SLS)

$44/hr 1 week Polycarbonate TrueForm SandForm

light: 100%; margin: 0">Casting Patterns Concept Models

Stereolithography 250 (SLA)

$33/hr 2 weeks Epoxy Resin (Translucent)

Thin walls Durable Models

Z402 3-D Modeller (Jet)

$27.50/hr 1 week Starch/Wax Concept Models

Process:Laminated Object Modeling

(LOM) • Object made by deposition

and cutting of layers of tapes

• Introduced in 1991 by Helisys Inc of Torrance.

• Cubic and Helisys offer this technology

• Slow, sharp edges• Research on composites

prepregnated moldless manufacturing

• Inexpensive depending on accuracy, large scale models possible

• Slow and inaccurate (knives vs lasers)

LOM Objects

Fused Deposition Modeling (FDM)

• Extruder on a cartesian robot

• Extrudes thermoplast polymers “spaghetti”

• Moderately fast and inexpensive

• Stratasys is the market leader

• Functional parts, ABS and nylon

• Best choice for mechanical engineers and product developers !

• Can be used for direct digital manufacturing

• Systems starting from $14,000

FDMAbbreviation: FDMMaterial type: Solid (Filaments)

Materials: Thermoplastics such as ABS, Polycarbonate, and Polyphenylsulfone; Elastomers

Max part size (LxWxH):

36.00 x 24.00 x 36.00 in.

Min feature size:

0.005 in.

Min layer thickness:

0.0050 in.

Accuracy: 0.0050 in.Surface finish: RoughBuild speed: Slow

Most common FDM Systems

• High Res: – Dimension ELITE

• Large FootPrint (12x12)– Dimension SST1200

• Low cost – uPrint ($14,900)

• Do it Yourself:– FAB@Home– RepRap

Stereolitography (SLA)

• Patented in 1986• 3D System is the

market leader• Highest resolution and

smoothness• UV Laser beam cure

cross-sections of parts in a liquid batch of photoreactive resin

• Subvariants: DLP entire layer projection

Stereolitography (SLA)

Selective Laser Sintering (SLS)

• Can be used for both thermoplastics and metal

• Powder is fed into a continuous layer

• Laser is used to fuse/sinter powder particles layer-by-layer

• Produces functional parts

• Layer thickness 0.004” or less

SLS samples

3D Printing• Layer of powder is first

spread across build area• Inkjet-like printing of

binder over the part cross-section

• Repetition of the process with the next layer

• Can produce multi-colored parts

• Useful only for presentation media

• Lowest resolution of all techniques

• Market Leader: Z-Corp

3D Printing

Electron Beam Melting (EBM)

• Dispensed metal powder in layers

• Cross-section molten in a high vacuum with a focused electron beam

• Process repeated until part is completed

• Stainless steel, Titanium, Tungsten parts

• Ideal for medical implants and injection molds

• Still very expensive process

Examples of EBM

Do it Yourself FDM rapid prototyping(cost under $5K) • FAB@Home • RepRap

The Future ? Self-replication !

RepRap achieved self-replication at 14:00 hours UTC on 29 May 2008 at Bath University in the UK. The machine that did it - RepRap Version 1.0 “Darwin” - can be built now - see the Make RepRap Darwin link there or on the left, and for ways to get the bits and pieces you need, see the Obtaining Parts link.

Questions and Answers ?

Rapid Prototyping Process Flow

• Solid Modelling• Tesselation/Generation of STL file• Support Generation• “Slicing” of the Model • Model Physical Buildup• Cleanup and Post Curing• Surface Finishing