Rapid Prototyping by Layered Manufacturing

Product Realization Cycle Mock-Up’s, Engg prototypes

Why speed up prototyping?

Quick product entry into market captive market.

Lower operating costs of development group

Longer PRP time higher reluctance of managers to change existing technologies causes stagnation of products

Rapid Prototyping

Rapid prototyping =quick fabrication of geometric shapepossibly use different materials than designed materialspossibly use different process than production process

Uses of prototype models:

1. Aesthetic Visualization

2. Form-fit-and-function testing

3. Casting models

Layered Manufacturing Processes

Stereolithography

Selective Laser Sintering

Fused Deposition Modeling

Laminated Object Manufacturing (LOM)

Three Dimensional Printing (MIT ZCorp)

Laser Engineered Net Shaping

Stereolithography (SLA)

1. Raw material: viscous resin2. Part constructed in layers of thickness t3. Supporting platform in container at depth t3. UV laser solidifies part cross-section4. Platform lowered by t5. Part cross-section computed at current height + t6. Repeat Steps 4, 57. Removed completed part,8. Break off supporting structures9. Cure the part in oven. He-Cd Laser

UV beam

Rotating mirrorHigh-speedstepper motors

Focusing system

Liquid resin

Part

Platform

Elevation control

Support structures

He-

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Las

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Sen

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SLA: companies and applications

Companies that develop and sell SLA machines:1. 3D Systems™ Inc. (www.3Dsystems.com)2. Aaroflex Inc (www.aaroflex.com)

Shower head

Automobile Manifold(Rover)

Selective Laser Sintering (SLS)

1. Deposit layer of powder on platform.2. The CO2 laser solidifies part cross-section3. Lower platform by t4. Deposit new layer of powder above previous layer5. Repeat steps 2-4 to complete part5. Shake away surrounding powder (re-used)6. Bake model in oven to sinter (melting point – )*7. Diffuse lower MP metal to fill pores**

SLS: companies and applications

First commercialized by Prof Carl Deckard (UT Austin)Marketed by DTM Corp.DTM acquired by 3Dsystems Inc.

1. 3D Systems™ Inc. (www.3Dsystems.com)

2. EOS GmbH, Munich, Germany.

[both examples, source: DTM inc.]

Plastic parts using SLS Metal mold using SLS, injection molded parts

Fused Deposition Modeling (FDM)

Z-motion

Melting head withXY-motion

Build materialwire spools:(a) Part (b) Support

Extrusion nozzles

Part

SupportFoam base

Part constructed by deposition of melted plastic 1. A 0.05” wire of plastic pulled from a spool into head2. Plastic is melted (1ºF over MP)3. Molten plastic extruded through the pen nozzle to build layer

Materials:ABS, Polycarbonate (PC),Polyphenylsulfonen (PPSF)

FDM: companies and applications

FDM™ is a patented technology of Stratasys™ Inc.

Monkey Cinquefoil Designed by Prof Carlo Sequin, UC Berkeley5 monkey-saddles closed into a single edged toroidal ring

Gear assembly Toy design using FDM models of different colors

Laminated Object Modeling (LOM)

1. Paper is pulled across the table2. Laser beam cuts the outline of the part, plus removal grids3. A large, fixed size rectangle surrounding the part is also cut.4. The table is lowered by t (= paper thickness)5. Fresh paper rolled on top of the previous layer6. Laser cuts new layer 7. A heated roller activates glue to stick the fresh layer8. Repeat steps 4-7 to complete part9. Break away removal blocks to get final part

LOM: companies, applications

Original technology developed by Helisys Inc.;Helisys acquired by Corum.

1. Cubic Technologies Inc [www.cubictechnologies.com]2. KIRA Corp, Japan [www.kiracorp.co.jp]

[source: Corum Inc] [source: KIRA corporation]

3D printing

Technology invented at MIT, Part constructed with starch powder

1. Layer of powder spread on platform2. Ink-jet printer head deposits drops of water/glue* on part cross-section3. Table lowered by layer thickness4. New layer of powder deposited above previous layer5. Repeat steps 2-4 till part is built6. Shake powder to get part

*Materials used: starch, plaster-ceramic powder* Multi-colored water can be used to make arbitrary colored parts (same as ink-jet printing)

3D Printing: companies, applications

1. Z-corporation [www.zcorp.com]2. Soligen [www.soligen.com]

Engine manifold for GM racing carCast after Direct Shell Production Casting[source: www.soligen.com]

Laser Engineered Net Shaping (LENS)

Technology invented at Sandia Labs, USA, Part constructed with metal powder

1. High power laser melts site of deposition1. Powder deposited by nozzle into hot-spot2. Laser builds cross-section in raster-scan fashion3. Table lowered by layer thickness4. New layer constructed on top of previous layer5. Repeat process till build is complete

LENS: companies, applications

1. Optomec Inc, USA [www.optomec.com]

[source: www.optomec.com]

Rapid Prototyping: Model and Software

Repeated cross-section operations 3D CAD model is required

Cross-section of complex surfaces computationally slow+Typical LM process surface accuracy is low (10-50)

Approximation model is used: STL models

STL models: Triangulated, surface models

STL format

All commercial CAD systems can convert 3D models STL

User specifies accuracy:Higher accuracy many, small triangles large files

STL Rules:1. Surface of arbitrary (finite) genus object can have holes2. Multiple shells are allowed (assemblies)3. Surface must be closed4. Vertex-to-vertex rule

WRONGCORRECT

Rapid Prototyping by Layered Manufacturing

a

c

b

valid:a b cb c a, etc.

invalid:b a c, etc.

outwardnormal

a

c

b

valid:a b cb c a, etc.

invalid:b a c, etc.a

c

b

valid:a b cb c a, etc.

invalid:b a c, etc.

outwardnormal

The ASCII STL File FormatSolid [name][facet normal [nx] [ny] [nz] outer loop vertex [v1x] [v1y] [v1z] vertex [v2x] [v2y] [v2z] vertex [v3x] [v3y] [v3z] endloopendfacet]+endsolid [name]

Remarks

About STL:

STL is de facto standard for all RP technologies

ASCII STL files are LARGE, Binary format is more compact

About LM:

Expensive, but gaining popularity

First popular technique: SLACurrently (2006) most popular: FDM