Page 63 - Making things move_ DIY mechanisms for inventors, hobbyists, and artists

44 Making Things Move

The type of plastic you’re looking for, and how much you need, will help determine
where you can find it. As always, starting at the McMaster site is convenient.
However, plastics are so popular that you can likely find what you need at a local
arts-and-crafts store like Pearl (www.pearlpaint.com) if you’re looking for common
shapes and sizes like sheets or rods.
Foams, rubbers, and plastics for molds and casted parts fall in this section as well.
Insulation foam (the harder, pink and blue kind) and RenShape foam are popular for
prototyping. Smooth-On (www.smooth-on.com) makes dozens of materials for
prototyping, sculpting, and model making. The Compleat Sculptor (www.sculpt.com),
based in New York City, is one of Smooth-On’s distributors, and a one-stop shop for
everything you could ever need for molding and casting. We’ll talk more about this
process in Chapter 9.

For more do-it-yourself (DIY) versions of shaping your own plastic parts, check out
ShapeLock Design Plastic and Sugru. Both of these products are plastics that you can
mold and shape by hand, and then let harden at room temperature. Depending on
your application, don’t overlook Tupperware or toy sets like LEGO and K’NEX for
structural parts and housings.

Composites
Composites are similar to alloys in that two or more materials are mixed together to
combine the favorable characteristics of each. However, metal alloys mix only types of
metal, while composites can mix materials across different material groups, such as
fiberglass and carbon fiber. For example, composites are being used increasingly in the
newest airplanes, including the Airbus A380 and Boeing 787. Composites are lighter
weight but still strong, so the plane uses less fuel to cover the same distance. Rapid
prototyping companies like Solid Concepts (www.solidconcepts.com), which we’ll talk
about more in Chapter 9, can use composites of aluminum, nylon, and glass to create
small functional parts for prototype designs.

Wood
Wood is actually a natural composite, made of strong cellulose fibers (think of them as
straws) held together by a stiff material called lignin (think of this as the glue around
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the straws). It’s relatively easy to work with and generally low cost.