Page 119 - Robot Builder's Bonanza

88 WORKING WITH PLASTIC

Figure 9-1 Plastic can be used for the entire robot
or just parts of it, like this all- plastic bracket for
mounting a radio control servo motor to a robot.

You can use plastic for the entire robot or just parts of it— mixing and matching materials
is not only allowed in robot construction, it’s encouraged. For example, the inexpensive motor
mount in Figure 9-1 is made of a lightweight plastic; you can combine the mount with robots
made of wood, any kind of plastic, metal, cardboard, or any other material.
Here’s a short rundown of the plastics that I find most useful in robotics:

ABS is short for “acrylonitrile butadiene styrene,” should you care about this sort of thing.
ABS is most often used in sewer and wastewater plumbing systems; it’s the large black
pipes and fittings you see in the home improvement store. But it can be any color, and
it can come in any shape; LEGO building blocks are made of ABS plastic. You can get
ABS plastic in sheets.
Acetal resin is called an “engineering plastic,” because it is designed to be used for various
engineering applications, such as making prototypes. It’s often referred to by one of its
brand names, Delrin. Acetal resin comes in sheet and block form.
Acrylic is the mainstay of the decorative plastics industry. It can be easily scratched, but if
the scratches aren’t too deep they can be rubbed out. Acrylic is somewhat tough to cut
because it tends to crack, and it must be drilled carefully. In the United States, acrylic is
often referred to by its most popular trade names, Plexiglas and Lucite. In the United
Kingdom, it’s Perspex.
Nylon is tough, slippery, self- lubricating stuff that is more commonly used in robotics for
lightweight screws and nuts. Many plastics distributors also supply nylon in rods and
sheets. It’s very difficult to glue anything to nylon.
Polycarbonate plastic is a cousin of acrylic but more durable and resistant to breakage. It
comes in rods, sheets, and tubes. Often sold as a replacement for glass windows, poly-
carbonate is fairly hard to cut and drill. Common brand names include Lexan, Hyzod,
and Tuffak.
Polyethylene (“polythene” in the United Kingdom and elsewhere) is lightweight and trans-
lucent and is often used to make flexible tubing. A variation of this plastic, called high-
density polyethylene, or HDPE, is used to make very durable kitchen cutting boards. I
like this stuff, but it’s very difficult (darn near impossible) to glue anything to it.
Polystyrene is a mainstay of the toy industry. Although often labeled “high- impact” plas-
tic, polystyrene is brittle and can be damaged by low heat and sunlight. It’s only mod-
estly useful in robotics and is mentioned here only because hobby model stores carry the
stuff in sheet form.

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