December 2007 Summary

Dr. Mileta Tomovic (of Purdue University's Department of Mechanical Engineering Technology) and graduate students Tamara Novakov and Jui Shyang Liu introduced us to the fascinating technology of rapid prototyping, which creates a prototype model of an invention rapidly (2 – 7 hours) and inexpensively. They have generously made the slides of their presentation accessible.

Embodying your inventive idea in a physical model can help you:

  • visually communicate your invention to investors, colleagues, and customers
  • optimize your invention before manufacture
  • test market your invention on a small scale
  • establish an invention date for your patent application
  • reverse engineer someone else's invention.

One form of rapid prototyping (known as material addition, additive fabrication, three dimensional printing, solid free-form fabrication, layered manufacturing, or computer automated manufacturing) uses a machine, and a description of your invention as Computer-Aided Design (CAD) data, to build a physical model of your invention.

The basic rapid prototyping process has 5 steps:

  1. create a CAD model of your design
  2. convert it to STL format (a format, native to stereolithography CAD software, which represents a 3-D surface of your invention as an assembly of planar triangles)
  3. slice the STL file into thin cross-sectional layers (a pre-processing program adjusts the size, location and orientation of the CAD model to correspond to the physical model you want)
  4. build the physical prototype model in layers (a machine, using one of several techniques, builds your model one layer at a time from polymers, paper, or powdered metal)
  5. clean and finish the model (remove the prototype from the printer, detach any supports, cure photosensitive materials, and sand, seal, or paint the model to improve its appearance and durability).

You can build a physical model of your invention from one of several different kinds of layers (each with its own advantages and disadvantages):

  • Liquid
    • polymer, electroset fluid, or molten material
  • Particles
    • fused by laser, or joined with a binder
  • Sheets
    • bonded with adhesive, or with light
Particular techniques used to form those layers include:
  • solidification of a resin via electromagnetic radiation
  • stereolithography
  • fused deposit modeling
  • selective laser sintering
  • 3-D printing
  • laser engineered net shaping
  • laminated object manufacturing
  • polyjet modeling

If you would like to apply rapid prototyping to your invention, consider contacting Randy Hountz of Purdue University’s Technical Assistance Program (TAP). TAP and the Department of Mechanical Engineering Technology help individuals and small companies that can’t afford a technical staff. Your first 40 hours of assistance with rapid prototyping are free. Available equipment includes the Optomec LENS 750, Zcorp Spectrum Z510, Prometal Z1, and Objet –Eden 350V.

Want to learn more? Try MIT's free OpenCourseWare Engineering Design and Rapid Prototyping.

We are most grateful to Dr. Tomovic and his students for their very interesting presentation.