Page 298 - Anatomy of a Robot

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MECHANICS 283
Metals
It’s easy to find a metal-forming shop in most cities. Further, metals are not difficult to
work with at home; just make sure all safety precautions are observed. Very hard met-
als can be difficult to use because they require (expensive) tools that are even harder.
Diamond studded (and other) tools are available for such work.

Plastics

Plastics can be molded, melted, and altered by machine to change their shape. Molds
are expensive, in general, to build. Vacuum forming is a reasonable alternative for mak-
ing thin sheets of plastic into the required shapes. Plastics can undergo machine work,
even at home, but the material tends to foul the tools.

Composites

Composites can be used much like fiberglass. They can be difficult to control but offer
very good strength for their weight. Metal, wood, and plastics are relatively well known
materials. Composites, on the other hand, are newer and are just finding their way into
consumer products like bicycles. These materials are built very much like fiberglass.
Fibers, in the form of woven mats, are impregnated with a filling material that reinforces
the fibers. The strength is largely in the direction of the fibers, not across the fibers.
Some care must thus be taken in the design and layout of the fibers within the robot
chassis. Common fibers used include glass, carbon fibers, and plastic fibers. Many dif-
ferent resin materials exist, such as epoxy and polyurethane. Filler materials, like short
glass fibers, are available to make the resin stronger as well. The Market Development
Alliance web site contains some good definitions of other materials’ mechanical prop-
erties at www.mdacomposites.org.
The previously mentioned Market Development Alliance web site and the Com-
posites Fabricators Association (www.cfa-hq.org/) are great sources of information
about composites.

Wood
Wood is easy to work, but not very strong. Watch out for termites!