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Advantages |
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CARP |
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RP Processes |
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Available Casting Methods |
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RP Decision Process |
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Tech Data Required |
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Cost Justification |
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RP Industry Resources |
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Case Studies |
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The future for RP |
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Provides a method for fast delivery on low
volume quantities |
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Reduces Product Lead Time for first run approval |
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Rapid turnaround for emergency buys to maintain
Mission Readiness |
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Eliminates costly hard tooling amortization |
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Provides accurate prototypes for redesigns |
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Allows tooling to be easily recreated upon
requirement - no need to buy or store hard tool |
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PLT reduced |
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Fast tooling for short runs |
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Competitive dimensional quality |
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Relatively low cost |
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Most foundries can cast using RP tools |
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Relatively short production life |
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Tool material selected may impact manufacturing
life |
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Surface finish not perfect |
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Build envelope for RP processes |
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Post-processing needed for most RP methods |
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Weaker tooling mechanical properties |
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Mass conservation (Continuity equation) |
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Newton¡¯s second law of motion (Momentum equation) |
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First law of thermo-dyamics (Energy equation) |
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Calculation of a shrinkage for each element from
the actual temperature field and density curve; |
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Calculation of feeding regions (which will be
supplied from one of the feeders); |
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Calculation of the total shrinkage from all the
feeding regions; |
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Calculation of the convection heat transport
through feeder necks. |
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Processes |
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SLA: a light and heat sensitive polymer based RP
process |
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ThermJet |
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KelTool |
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Advantages |
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High resolution, good surface, wide application,
larger build envelope |
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Disadvantages |
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Support structure required, post-curing, liquid
materials |
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Common applications |
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How the process works |
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Paper sheet based laser profile cutting |
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Advantages |
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Wood like, hard |
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No support required |
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Disadvantages |
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Delamination is possible |
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Not good for small and thin wall features
(<.2¡± in size or < 0.1¡± in thickness) |
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Common applications |
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How the process works |
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A sand based laser sintering process |
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Advantages |
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No support and post-processing needed |
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Multiple material options |
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Disadvantages |
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Surface finish is typically rougher |
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Common applications |
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How the process works |
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A extrusion process of fused plastic materials |
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Advantages |
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Desktop size, very good for small size features |
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Disadvantages |
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Weaker tool strength |
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Common applications |
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How the process works |
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A polymer based with laser mask usage |
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Advantages |
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High resolution and dimensional accuracy |
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Disadvantages |
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Expensive and long building time |
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Common applications |
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How the process works |
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A powder based bond material deposited process |
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Advantages |
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No support needed |
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Disadvantages |
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Post-cure needed |
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Common applications |
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How the process works |
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Wax injection process |
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Advantages |
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High resolution, suitable for office |
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Disadvantages |
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Part size is small |
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Common applications |
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3D Systems: SLA (Stereolithography Apparatus) |
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Helysis: LOM (Laminated Object Manufacturing) |
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DTM: SLS (Selective Laser Sintering) |
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Stratasys: FDM (Fused Deposit Modeling) |
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Z Corp: 3DP (3 Dimensional Printing) |
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Cubital: SGC (Solid Ground Curing) |
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Sanders: Sanders Printing |
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Investment Casting |
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Sand Casting |
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Plaster Casting |
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Die Casting |
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1988 -- 3D Systems, Inc. ships first
Stereolithography (SL) machines (SLA-1) |
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1988 -- First investment castings from SL
patterns -- Pratt & Whitney and Precision Castparts Corp. |
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1988 -- Desoto Inc. develops first SL resin for
investment casting patterns |
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1989 -- Some foundries resurrect the ¡°flask¡± or
¡°solid¡± mold method for use with SL Patterns |
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1990 -- Allied Signal starts government funded
study to establish the capability to produce investment castings from SL
patterns |
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1991 -- Stratasys, Inc. produces investment
casting wax patterns with Fused Deposition Modeling (FDM) process. |
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1991 -- MIT develops 3D printing process for
ceramic cores and shells using inkjet technology. |
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1991 -- DTM Corporation produces investment
casting wax patterns with Selective Laser Sintering (SLS) process. |
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1992 -- Soligen, Inc. licenses MIT process and
develops machine and Direct Shell Production Casting (DSPC) process. |
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1993 -- 3D Systems introduces ¡°Quick Cast¡± and
epoxy resin designed for investment casting |
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1993 -- DTM offers polycarbonate material as
improvement for investment casting patterns |
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1994 -- 3D Systems offers Ciba-Giegy epoxy resin
for SLA-500 -- larger casting patterns |
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1995 -- Sanders machine produces investment
casting patterns for small, intricate parts |
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1996 -- DTM announces ¡°Trueform¡± as improved
investment casting pattern material |
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Independent Factors: Factors that are determined
independently of tool path selection |
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Dependent Factors: Outcomes that result based on
the tool path selected |
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Data Status |
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Production Volume |
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Prototype or Production |
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Who Will Use the Tooling |
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Part Geometry |
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Cores |
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Parting Line Complexity |
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Draft |
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What Geometrical Features are Important |
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Pattern Shop Capability |
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Tool Cost |
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When more than one tool decision is feasible,
cost can be a major deciding factor |
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Lead-Time |
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Determined by the tool decision selection |
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If critical, rapid tooling must be used |
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Required Accuracy |
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If low priority, manual, CNC, and FFFF may be
equally viable |
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If high priority, CNC may be the only choice |
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Tool Durability |
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Depends on tool material |
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Material affects fabrication method &
resultant cost & time |
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Existing Physical Part |
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2D Drawing or 2D CAD File |
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Intermediate Representation |
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Special purpose file created by CAD System |
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e.g., STL, IGES, STEP, etc. |
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3D CAD Solid Model |
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Exactly defines part geometry |
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Ideal for rapid tooling |
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What decision combinations are feasible? |
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What is the ¡°best¡± choice? |
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Each cell represents a different combination of
tool path decision variables |
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45 possible tool decisions given the choices
shown |
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Many more choices are possible |
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Over-riding consideration |
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Tool approach must produce desired geometry |
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The ¡°best¡± tool path depends on particular
features |
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Wall thickness |
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Aspect ratio |
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Undercuts and coring complexity |
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Cross-section geometry |
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Surface complexity |
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Decision is very dependent on the decision
maker¡¯s experience and judgement |
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Process is highly iterative and non-linear |
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May involve several conversations with the
customer |
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May involve design change |
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Final tool path decision evolves as the customer
and tool builder work together |
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Verifies theoretical understanding |
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Dimensional accuracy of tool |
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Lead-time for tool |
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Life of tool |
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Examples |
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Time, cost and accuracy is a tradeoff. You may
decrease expectation of one aspect if you increase the requirements of
another. |
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Studies shows that it is estimated 10% to 50% of
costs may be reduced by using RP-based tooling depending on the part
geometry, complexity and size comparable to traditional manual making or
CNC machining. |
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Part |
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Motor Housing |
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Casting process |
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Investment Casting |
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Source |
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Rapid News |
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Vol. 2 No. 4 |
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4 measurements were taken in each region and
averaged to determine the actual part dimensions. |
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Dimensional accuracy is calculated by the difference
between the electronic part file dimensions and the actual RP part model. |
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3D CAD solid files |
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STL files |
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Accuracy requirements - dimensional tolerances |
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Material |
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Product volume |
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Lead time |
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Critical features |
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AFS Search Engine |
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Service bureaus |
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Clinkenbeard Associates, Inc |
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Solidiform Inc. |
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K+P Agile Inc. |
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Web Sites |
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NWU FFFF Project Homepage |
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Time-Compression Locator |
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Clemson Univ. RP Resource Page |
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2D Drawing |
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3D CAD model (add draft and shrinkage) |
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Tool design (core box and pattern design) |
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Tessellation (.stl format) |
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LOM preparation and parameter setting |
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LOM production |
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Post-processing |
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Foundry processes |
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Envelop Dimensions: 7.7 x 6.4 x 2.3 inches |
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Materials: Steel |
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Suggested Tooling Process |
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Tool Fabrication Method: LOM |
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Pattern Material: LOM Paper Model |
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Tooling Approach: Cope & Drag |
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Note: Time maybe same for CNC and LOM, but cost
of LOM tooling is a little bit cheaper. |
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For large production volume, Cope & Drag is
recommended. |
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Envelop Dimensions: 11 x 11 x 2.5 inches |
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Materials: Cast Iron |
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Tool Fabrication Method: LOM |
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Pattern Material: LOM Paper Model |
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Tooling Approach: Loose Pattern |
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Note: Cost and time are same for CNC and LOM. |
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LOM choice based on further consideration of
geometry, volume, and equipment availability |
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Envelop Dimensions: 25 x 6 x 4.5 inches |
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Materials: Cast Iron |
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3 Pieces: Loose LOM pattern with 2 cores |
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30 pieces: Mounted CNC wood pattern with gating |
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300 pieces: CNC wood cope and drag |
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Note: although LOM or CNC is recommended, manual
may be preferred if lead-time is critical |
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Manual is faster because of part geometry |
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Higher dimensional accuracy |
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Better mechanical properties |
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Faster building speed |
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Less post processing |
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No or less support generation |
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Automatic RP process selection |
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Automatic foundry tooling selection |
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CARP system |
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Virtual Prototyping |
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RP vendors/systems |
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RP process/tooling selection |
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RP use in industry |
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RP applications (case studies) |
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Notes