Rapid Prototyping (RP), Additive Fabrication, Direct Digital Manufacturing, 3D Printing are just four of the many different ways to describe the twenty-two -year old industry based on technologies that build parts up, layer by layer.  For the designers new to the technology, the promise is the same: 

Everything drawn 3D CAD can be sent to a 3D Printer.

If only product design was that easy.   When your design process involves rapid prototyping, knowing about the materials and process can improve the outcome of your prototype.

There are two equally false thoughts about prototyping materials:

      • RP parts are super fragile and super expensive – DON’T DROP THE PROTOTYPE!

      • RP materials come from “unobtainium” and are a perfect match for all designs and assemblies

Although the first notion was probably true ten years ago, things have improved dramatically.  Materials are stronger and better mimic the engineering polymers intended for production parts.  Also, lower cost processes have reduced the overhead of many suppliers.  For many processes, ordering a second piece only adds a fraction of the cost of the first.  Since your marketing manager is going to keep the first model, might as well order two so you have one to use to communicate with engineering and manufacturing. 

Of course, the thought that RP machines can make everything is equally false.  If your design includes sheet metal, expect to make some thickness changes before sending the STL file to the model shop.  Many assemblies incorporate multiple materials to optimize the design for strength or weight.  Do not expect one RP material to cover that very wide range of material properties. 

So, what is a designer to do?  First, think about your design and product development goals.  Then pick a prototyping strategy that best meets those goals. 

General design considerations:

  • When Outsourcing

     - Match your design with the right process

          • Small medical device?  SLA

          • Color concept model?  Z Corp

          • Over molded plastic/rubber?  Objet

     - Be realistic about lead times

        • Start to finish with shipping time, outsourcing takes a week

        • Give your supplier a heads up when projects are on the way

      - Understand cost and time drivers        • Material Volume

        • Build Envelope

        • Post Processing

  • In House 3D Printing

     - Know the strengths and limits of your process
       • Modify the design to make post processing easier

       • Know when to use assemblies, and when to manually assemble components

       • Use hollow or sparse builds to minimize costs

   - Understand support materials and post processing

   - Determine how to make the build more efficient.  What drives time? 

Just like most other manufacturing processes, RP appreciates good design.  Simple rules like constant or similar wall thicknesses help make growing and processing the parts much more efficient.  Cantilevered beams often need support, and sheet metal features need to be thickened.  Most importantly, using good design sense and understanding how your parts are made will helpyou make better designs in less time with less money.

Bill Watson, IDSA is the managing partner of Anvil Prototype & Design (www.AnvilPrototype.com), a Z Corporation partner and RP service bureau based in Charlotte, NC.