rapid prototyping & manufacturing (rpm)

ENGI 7962 Computer-Aided Engineering

Rapid Prototyping & Manufacturing (RPM)


Outline• Why RP&M Technology?• Basic Principles• Currently Available/Developing Systems• Directions for RP&M Research


R&D Directions in Manufacturing

• Intelligent Manufacturing Control• Equipment Reliability & Maintenance• Advanced Materials• Product Realization• Education & Training


Product Realization• Multidisciplinary• Concurrent, life cycle design teams• Intelligent product models• Common databases across all functions

(eg. engineering, planning, marketing, ...)• Management of PRP• Time to market is critical and prototypes

used to aid communication


History of Prototyping• Artist/Craftsperson created model• Development of CAD• CAD databases used to generate CNC

programs. Subtractive processes.• Development of additive processes ...

generally called “Rapid Prototyping”.


Definition

• A process by which a solid physical model of a part is made directly from a 3-D CAD drawing without unique tooling or fixtures.

• Referred to as– Desktop Manufacturing– Automated Fabrication– Tool-less Manufacturing– Free-form Fabrication


Goals of Rapid Prototyping• Substantially reduce product development

time, through rapid creation of 3D models.• Improve communication (visualization)

within multidisciplinary design teams.• Address issues of increased flexibility &

small batch sizes, while remaining competitive (rapid manufacture).


Basics• Require a geometric model.• Must include surface information.• Usually solid modeling system:

• CATIA, I-DEAS, Pro/Engineer, SolidWorks, etc

• Surface models require completely bound volume and internal detail.


Basics (continued)• 3D geometric model is mathematically

sectioned into parallel cross-sections.• Each cross-section creates a 2D binding

or curing path for model construction.• Models are constructed one layer at a time

until complete. Supports may be required.• Two stages: Data preparation and model

production.


Data Preparation• CAD data converted to .STL format.• .STL designed for 3D Systems Inc.

Stereolithography Apparatus (SLA).• Triangular facets are used to describe the

shape of a closed 3D model.• Faceted surface must be completely

bound.• Curved surfaces are approximated.


.STL Format• Developed by Albert Consulting Group• Consists of x, y & z coordinates of triangles• Example:

solid...

facet normal 0.00 0.00 1.00outer loop

vertex 2.00 2.00 0.00vertex -1.00 1.00 0.00vertex 0.00 -1.00 0.00

endloopendfacet

...endsolid


.STL Format (continued)• All adjacent triangles must share two

vertices.• Translation software is either included in

CAD package or third party.• Translator should provide ability to adjust

chordal deviation (ie. trade-off accuracy vsfile size and processing time).


VRML vs .STL• Virtual Reality Modeling Language• Developed through Silicon Graphics using their

Open Inventor (.iv) standard.• Lead to “Tele-Manufacturing” as proposed by

Michael Bailey, U. of C., San Diego• Take advantage of greater development effort

and utilize other features (e.g.. colour, colourgradient, texture).

• STL still the dominant RP format


RP Production Technologies• Stereolithography Apparatus presented at

Autofact show in November, 1987. • Currently upwards of twenty different

technologies being developed/marketed.• Major differences in materials used and

build techniques.• Various RP technologies outlined in

following slides.


Stereolithography Apparatus (SLA) - 3D Systems

• Laser generated ultraviolet beam traces out cross-section & solidifies liquid polymer.

• Component is built in vat of liquid resin.• Vat size limits prototype

• SLA-190 (7.9 x 7.9 x 9.8”) US$105,000• SLA-250 (10 x 10 x 10”) US$210,000• SLA-250 (20 x 20 x 24”) US$420,000


Stereolithography Apparatus


Stereolithography (cont.)• Materials - five currently available. All are

acrylates (non-reusable thermosets).• Accuracy - ranges from 0.1% to 0.5% of

overall dimension from small to large parts. A very accurate RP technology.

• Curing stability and support structures remain challenges.


Solid Ground Curing / Photo-masking - Cubital Ltd.

• Uses photo-masking to solidify whole layers of photopolymer at one time.

• Solider 5600 (20 x 14 x 20”) US$550,000 with machine dimensions 13.5’ x 5.5’ x 5’

• Layer thicknesses of .004-.006” and dimensional accuracy of 0.02”, building up to 100 layers/hour.


Solid Ground Curing (cont.)


Solid Ground Curing (cont.)• Full cure as built minimizes shrinkage and

eliminates post-curing.• Wax eliminates need for supports.• Fly cutter provides for “undo” operation.• System produces a lot of waste. Can’t

reuse material picked up during milling, and uncured resin is a hazardous material.


Selective Laser Sintering -DTM Corp

• Developed at U. of Texas at Austin• Utilizes powder, rather that liquid polymer.• Potential exists for different materials

including polycarbonate, PVC, ABS, nylon, polyester, polyurethane and casting wax.

• Sinterstation 2000 (12” dia. x 15” dp) US$425,000. Builds .4 - 2” per hour.


Selective Laser Sintering (cont.)


Selective Laser Sintering (cont.)• Layers from .003 - .02” thick. Accuracy

from .005 to .015” depending on size.• Components can be recycled by crushing

and converting back to powder.• Research is going into materials such as

powdered metals, ceramics and composites.


Laminated Object Manufacturing

• Process uses bonded sheet material. Normally paper, but metals, plastics and composites are possible.

• LOM-1015 (14 x 15 x 10”) US$95,000 LOM-2030 (30 x 20 x 20”) US$180,000

• Sheets of .002 - .02” thick.• Accuracy of +/- 0.005” achievable.


Laminated Object Manuf. (cont.)


Laminated Object Manuf. (cont.)• Support provided by remainder of sheet.• Prototypes less fragile than polymers.• No internal stresses or curing shrinkage.• Paper waste is non-hazardous.• Machine can be operated in an office

environment.• Cannot build hollow cavities as single part.


Three Dimensional Printing -MIT

• Utilizes powdered material, spread out one layer at a time.

• Adhesive is applied in droplets through a device similar to an inkjet printer head.

• Limited quantitative data available on accuracy.

• 3DP licensed to Soligen Inc. for Direct Shell Production Casting process.


Three Dimensional Printing (cont)


Three Dimensional Printing (cont.)

• Internal supports not required.• May require post processing, depending

on material and binder.• Work continues on limiting impact of

binder drops, reducing jagged “print”edges and flow control for the binder.

• Consortium includes Boeing, Hasbro, Johnson & Johnson, 3M & United Tech.


Other RP Systems• Fused Deposition Modeling - Stratasys

• uses .050” dia. thermoplastic filament

• Ballistic Particle Manufacturing - BPM • uses three axis robotic system controlling an ink jet like deposition

head. Low cost, easy to operate system.

• Electrosetting - U.S. Navy• 2D profiles are used to “plot” electrode shapes which are attached

to foil. Multi-layer foil sandwich is immersed in liquid and energized. Material inside electrode solidifies. Separately controllable voltage and current provides for programmable density, hardness, etc.


Other RP Systems (cont.)• Masking & Depositing - Carnegie Mellon

• robotic control of metal spraying through a disposable, laser cut, mask. A complementary mask is used to spray low melting point support alloy.

• Shape Melting - Babcock & Wilcox• controlled placement of gas metal arc welding wire weld deposit.

Very closely controlled and monitored thermal conditions with localized cooling allow for control over material properties.

• Innumerable Variations


R & D in Rapid Prototyping• Part Accuracy Improvement

• mathematical– use of CSG and ray tracing vs .STL– improved facet approximations

• process related– z step resolution– layer registration

• material related– material selection/development– stress relief, alternate build techniques to reduce deformation– additional processing (eg. shot peening)


R & D in Rapid Prototyping (cont.)

• Materials• improvements to current materials

– current materials weak and fragile– development of low-shrink, less brittle plastics– introduction of glass, carbon or graphite fibre– mixtures including ceramics are being tested

• focus on end-use material requirement– develop techniques to build with metal– low melting point, binary metal powders– deposition of droplets of molten metal from a moving nozzle– breakthrough RP design based on materials knowledge


R & D in Rapid Prototyping (cont.)

• Systems• improvements to current technologies

– incremental improvements to specific RP technologies– generic improvements, applicable to several RP types

• development of new RP technology• development of implementation knowledge

– desktop manufacturing, automated fabrication, tool-less manufacturing, free form fabrication

– workplace implications– application identification and development

• virtual manufacturing, communications• the personal factory


Examples of RP in Research• Molecular Modeling

• Protein Kinase• Molecular Docking Sites

• Earth Science• Bathymetry• Fault modeling• Terrain surfaces• Hurricane / meteorological modeling• Ozone Hole over Antarctica


Examples of RP in Research• Mechanical

• Specific component models• Clearance, fit, function verification• Design process development

• Medical• Creation of mold blanks• Customized devices for specific patients

• Mathematical Surface Visualization


Introduction to Rapid Tooling

• Defn: A process by which RP technology is used to allow manufacturers to speed up the prototype tooling process without committing to costly and time consuming hard tooling.


Rapid Tooling

• Evolved dramatically in 1996• RT allows user to build a tool that can

produce 100s, 1000s, or even 1000000s of parts quickly and at a lower cost.


The Evolution of RT

Rapid Soft Tooling (RST)

Rapid Bridge Tooling (RBT)

Rapid Hard Tooling (RHT)


The Evolution of RT


Rapid Soft Tooling (RST)

• Tools are made using RP• Parts are molded using

– Room Temperature Vulcanization (RTV)– Vacuum Casting– NOT Injection Molded

• NOT fabricated from end use material• Typically less than 30 parts per mold


Rapid Bridge Tooling (RBT)

• Utilizes advanced RP techniques• Accurate Clear Epoxy Resins (ACES)• Injection molded parts• Use of ACES allows entire project from

CAD design to 100 molded prototypes in 5 days.


Rapid Hard Tooling (RHT)

• Fabricate the RP part• Cover part with flexible silicon rubber• Break apart and send to local foundry• Ceramic part replica of RP part• Aluminum tooling cast from ceramic part• Parts can be “shot” in real production

material

rapid prototyping & manufacturing (rpm)

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