Design forDesign for EngineeringEngineering

Unit 6- Research and Development

Rapid Prototyping Systems

Rapid prototyping, is the automatic construction of physical objects using solid freeform fabrication. The first techniques for rapid prototyping became available in the 1980s and were used to produce models and prototype parts. Today, they are used for a much wider range of applications and are even used to manufacture production quality parts in relatively small numbers. Some sculptors use the technology to produce complex shapes for fine art exhibitions.In brief, rapid prototyping takes virtual designs (from computer aided design (CAD) or from animation modeling software), transforms them into cross sections, still virtual, and then create each cross section in physical space, one after the next until the model is finished. It is a WYSIWYG process where the virtual model and the physical model correspond almost identically.

Stereolithography exampleStereolithography exampleStereolithography is one "flavor" of a technology called Stereolithography is one "flavor" of a technology called Rapid Prototyping. This gives one the ability to "print" Rapid Prototyping. This gives one the ability to "print" out a CAD/CAM computer model in three dimensions. out a CAD/CAM computer model in three dimensions.

Just as you can currently print out a drawing in 2-D Just as you can currently print out a drawing in 2-D right now, rapid prototyping allows you to print an right now, rapid prototyping allows you to print an

OBJECT.OBJECT.It works by taking a computer model and "slicing" it into It works by taking a computer model and "slicing" it into thousands of very thin layers. Each of these layers can thousands of very thin layers. Each of these layers can be laid down, one at a time, by a device printing with be laid down, one at a time, by a device printing with

plastic (which is often called "Fused-Deposition plastic (which is often called "Fused-Deposition Modeling", or FDM), or with thin layers of paper, or Modeling", or FDM), or with thin layers of paper, or metal foil, or ceramic, or various other materials. metal foil, or ceramic, or various other materials. Stereolithography uses lasers to photochemically Stereolithography uses lasers to photochemically harden special liquid chemicals into a solid plastic harden special liquid chemicals into a solid plastic

form. Whichever method is used, over time, each layer form. Whichever method is used, over time, each layer builds up, until you have a completed modelbuilds up, until you have a completed model

               

This is a custom laser-cut pterosaur puzzle as an example of how you can use two-dimensional pieces to build a three-dimensional part                            

Laser cutting example

Fused Deposition ModelingFused Deposition Modeling

FDM is a rapid prototyping process used FDM is a rapid prototyping process used to produce functional ABS thermoplastic to produce functional ABS thermoplastic models directly from CAD data. The models directly from CAD data. The system utilizes a CNC controlled extruder-system utilizes a CNC controlled extruder-head which squeezes a fine filament of head which squeezes a fine filament of melted thermoplastic through a nozzle. melted thermoplastic through a nozzle. The nozzle deposits the heated plastic The nozzle deposits the heated plastic layer-by-layer to form the desired shape. layer-by-layer to form the desired shape. The liquid material hardens immediately The liquid material hardens immediately on contact in the cooler environment. on contact in the cooler environment.

Laminated Object ManufactureLaminated Object ManufactureIn this technique, developed by Helisys of Torrance, In this technique, developed by Helisys of Torrance, CA, layers of adhesive-coated sheet material are CA, layers of adhesive-coated sheet material are bonded together to form a prototype. The original bonded together to form a prototype. The original material consists of paper laminated with heat-material consists of paper laminated with heat-activated glue and rolled up on spools. As shown in activated glue and rolled up on spools. As shown in the figure below, a feeder/collector mechanism the figure below, a feeder/collector mechanism advances the sheet over the build platform, where a advances the sheet over the build platform, where a base has been constructed from paper and double-base has been constructed from paper and double-sided foam tape. Next, a heated roller applies sided foam tape. Next, a heated roller applies pressure to bond the paper to the base. A focused pressure to bond the paper to the base. A focused laser cuts the outline of the first layer into the paper laser cuts the outline of the first layer into the paper and then cross-hatches the excess area (the and then cross-hatches the excess area (the negative space in the prototype). Cross-hatching negative space in the prototype). Cross-hatching breaks up the extra material, making it easier to breaks up the extra material, making it easier to remove during post-processing. During the build, remove during post-processing. During the build, the excess material provides excellent support for the excess material provides excellent support for overhangs and thin-walled sections. After the first overhangs and thin-walled sections. After the first layer is cut, the platform lowers out of the way and layer is cut, the platform lowers out of the way and fresh material is advanced. The platform rises to fresh material is advanced. The platform rises to slightly below the previous height, the roller bonds slightly below the previous height, the roller bonds the second layer to the first, and the laser cuts the the second layer to the first, and the laser cuts the second layer. This process is repeated as needed second layer. This process is repeated as needed to build the part, which will have a wood-like texture. to build the part, which will have a wood-like texture. Because the models are made of paper, they must Because the models are made of paper, they must be sealed and finished with paint or varnish to be sealed and finished with paint or varnish to prevent moisture damage.prevent moisture damage.

Sources

http://en.wikipedia.org/wiki/Rapid_prototyping

http://www.pololu.com/lsrproj/lsrprj03/

http://www.sculptors.com/stereolithography.html

http://metals.about.com/library/weekly/aa-rp-fdm.htm

http://www.mne.psu.edu/lamancusa/rapidpro/primer/chapter2.htm#lom

Standards covered

Standard #2: Students will develop an understanding of the characteristics and scope of technology. BenchmarksAA. Requirements involve the identification of the criteria and constraints of a product or

system and the determination of how they affect the final design and development.BB. Optimization is an ongoing process or methodology of designing or making a product and is dependent on criteria and constraints.

Standard #10: Students will develop an understanding of the role of troubleshooting, research and development, invention and innovation, and experimentation in problem solving.Benchmarks I. Research and development is a specific problem-solving approach that is used

intensively in business and industry to prepare devices and systems for the marketplace.J. Technological problems must be researched before they can be solved.

Standard #13: Students will develop abilities to assess the impact of products and systems.BenchmarksJ. Collect information and evaluate its quality.K. Synthesize data, analyze trends, and draw conclusions regarding the effect of

technology on the individual, society, and the environment.