Manufacturing Processes Introduction to Rapid Prototyping

Background When developing a new product, there is always a need to see a single example or prototype. Idea is to catch any flaws or problems before a large investment is made in tooling and equipment. Can also reduce development time:analyze and debug design early. Need to be extremely competitive to beat competition to market.

History of Prototyping Began with Artists/Craftspeople creating hand-made models. Next was the evolution of CAD software. This lead to CAD databases being used to generate CNC programs (subtractive processes). Following subtractive processes was the development of additive processes ... generally called “Rapid Prototyping”.

Goals of Rapid Prototyping Allows for the creation of models at greater speeds and with more precision. Design process is improved as designers can experiment with variations of a product until the best results are obtained.

Goals of Rapid Prototyping Rapid prototyping can: 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).

Advantages Can produce physical model from CAD model in a matter of hours. Great tool for visualization and concept verification. Can use prototype in other manufacturing operations, such as casting and molding.

Basics A geometric model is required which must include surface information. Model is usually created in a solid modeling system such as Pro/Engineer, CATIA, I-DEAS etc. 3D geometric models are mathematically sectioned into parallel cross-sections. Each cross-section creates a 2D binding or curing tool path for model construction. Models are constructed one layer at a time until complete. Supports may also be required.

Stages There are two stages to rapid prototyping: (1) Data preparation. (2) Model production.

Stages 1. Data preparation. CAD data must be converted to .STL format. It is characterized by triangular facets that are used to describe the shape of a closed 3D model. Faceted surfaces must be completely bound. Curved surfaces are approximated.

Stages The .STL Format was developed by Albert Consulting Group. Consists of x, y & z coordinates of triangles. All adjacent triangles must share two vertices. Translation software is either included in the CAD packages or via third party. Resolution can be increased (# of triangles) Trade-off: accuracy vs file size and processing time.

Stages 2. Model production: There are major differences in materials used and build techniques within these technologies. Here is a list of various RP technologies: Stereolithography - 3D Systems Selective Laser Sintering - DTM Corp Laminated Object Manufacturing-Helisys Three Dimensional Printing - Developed by MIT Fused Deposition Modeling - Stratasys

Stereolithography - 3D Systems RP Technologies Stereolithography - 3D Systems

RP Technologies Stereolithography Apparatus (SLA) - 3D Systems Laser generated ultraviolet beam traces out cross-sections and solidifies the liquid polymer. Component is built in vat of liquid resin. Vat size limits prototype SLA-250 (10 x 10 x 10”) US$210,000 There are multiple materials currently available for the SLA. All are acrylates or epoxies (non-reusable thermosets).

RP Technologies Stereolithography Apparatus (SLA) - 3D Systems Accuracy - ranges from 0.1% to 0.5% of overall dimension from small to large parts. Currently the most accurate RP technology. Curing stability and support structures remain challenges.

RP Technologies Stereolithography Stages: CAD Design CAD Translator STL Verification Orient Support Prepare Build Post Process

Selective Layer Sintering (DTM Corp.) RP Technologies Selective Layer Sintering (DTM Corp.)

RP Technologies 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.

RP Technologies Selective Laser Sintering - DTM Corp Sinterstation 2000 (12” dia. x 15” dp) US$425,000. Builds .4 - 2” per hour. 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.

SLS CO2 Laser Laser Optics / Scanning Mirror Leveling Roller Powder Bed Build Chamber Powder Cartridge

SLS Process 1. Start with an STL file of your 3-D CAD data. 2. Enter the data into the Sinterstation system. 3. Spread a layer of powdered material. As the process begins, a precision roller mechanism automatically spreads a thin layer of powdered SLS material across the build platform.

SLS Process 4. Sinter a cross-section of the CAD file. Using data from the STL file, a CO2 laser selectively draws a cross section of the object on the layer of powder. As the laser draws the cross section, it selectively "sinters" (heats and fuses) the powder creating a solid mass that represents one cross section of the part.

SLS Process 5. Repeat. The system spreads and sinters layer after layer until the object is complete. 6. Remove the part. Once the part is complete, remove it from the part build chamber and blow away any loose powder. 7. Finish as desired. Use the part as is—or sand, anneal, coat, or paint it before using it for its intended application.

Laminated Object Manufacturing - Helisys RP Technologies Laminated Object Manufacturing - Helisys

RP Technologies 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 Sheets of .002 - .02” thick. Accuracy of +/- 0.005” achievable. Support provided by remainder of sheet.

RP Technologies Laminated Object Manufacturing Manufacturing prototypes less fragile than polymers. No internal stresses or curing shrinkage. Paper waste is non-hazardous. Need ventilation for smoke generated by paper burns. Cannot build hollow cavities as single part.

3 Dimensional Printing - Z Corp. RP Technologies 3 Dimensional Printing - Z Corp.

RP Technologies Three Dimensional Printing - Z Corp. -Utilizes powdered material (starch/cellulose), spread out one layer at a time. - Adhesive is applied in droplets through a device similar to an inkjet printer head. - 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.

RP Technologies Build Process - 3DP 1. The machine spreads a layer of powder from the feed box to cover the surface of the build piston. 2. System then prints binder solution onto the loose powder, forming the first cross-section. Where the binder is printed, the powder is glued together. The remaining powder remains loose and supports the layers that will be printed above.

RP Technologies Build Process - 3DP 3. When the cross-section is complete, the build piston is lowered slightly, a new layer of powder is spread over its surface, and the process is repeated. 4. The part grows layer by layer in the build piston until the part is complete, completely surrounded and covered by loose powder. 5. Finally the build piston is raised and the loose powder is vacuumed away, revealing the complete part.

Fused Deposition Modeling - Stratasys RP Technologies Fused Deposition Modeling - Stratasys

RP Technologies Fused Deposition Modeling Stratasys uses .050” dia. thermoplastic filament Gantry type robot moves extruder head in two principal directions over a platform. Thermoplastic is extruded through a small orifice in extruder head at 270 degrees F. As head moves, material is deposited over foam foundation. Supports are made of a different type of plastic. Can be easily removed by hand. Low cost, easy to operate system.

RP Technologies Fused Deposition Modeling (FDM) Stages CAD Design CAD Translator STL Verification Orient Slice Model Create Supports Create Roads Build Model Post Process

Areas of R&D dealing with Part Accuracy Improvement Mathematical area: potential use of CSG and ray tracing vs .STL improving facet approximations Process related area: increasing z step resolution developing layer registration Material related area: material selection/development considerations of stress relief, alternate build techniques to reduce deformation

Examples of RP in Research Molecular Modeling Protein Kinase Earth Science Fault modeling Terrain surfaces Mechanical Specific component models Clearance, fit, function verification Design process development Medical Creation of mold blanks Customized devices for specific patients Mathematical Surface Visualization