Page 177 - Robot Builder's Bonanza

146 RAPID PROTOTYPING METHODS

CONSTRUCTION FOAM
I’m using the term “construction foam” for the material used in buildings for subflooring,
insulation, and sound deadening. This material is commonly referred to as “blue foam,” and
represents a rather diverse family of molded and expanded polystyrene plastic.

G Though called “blue foam,” its color may be either blue or pink. The foam is available in
different densities, with many of the pink variety foams having the lowest density. You may find
the heavier blue foam easier to work with because it’s not as floppy.

Blue foam is from 1″ to 3″ thick, though specialty versions, such as floor sound- deadening
foam, are available in thinner sheets. This latter material can be found at flooring stores.
Rather than as a base all on its own, blue foam is most useful as a substrate or “rigidizer”
for your robot. It weighs very little for its size and bulk, yet offers remarkable rigidity. It’s best
used when physically cemented to another substrate, such as corrugated plastic or cardboard.
The two materials together provide a strong yet lightweight building platform for your robot.

PICTURE FRAME MAT BOARD
Pictures are often framed using a heavy paper mat. Mat board is available at any art supply
and picture frame store, and, depending on composition, is less than a dollar per square foot.
A common size is 16″ 20″, but it’s also available in larger sheets (not practical for mail
order), and precut into smaller pieces, such as 5″ 7″ or 8″ 10″. You can cut mat board
with a utility knife or with a specialty mat cutter. You can also get it custom cut for you at a
picture frame store; you can select squares, circles, and ovals.

Ask the sales assistants at the picture frame shop if they have any mat discards. When mat
G board is cut to make a picture frame, only the outside parts are used; the inner parts (the stuff of
most use to us robot builders) is thrown away. Ask nicely, and they may give you these pieces at
no cost.
While mat board may look like a piece of really thick paper, it’s actually composed of many
layers— plies— glued to one another. The typical quality 1/8″-thick mat has 8 to 12 plies.
While thicker mat board is available as a specialty item, it’s usually easier and cheaper to sim-
ply stack several 1/8″ boards together, cementing the stack using ordinary paper glue.

Cutting and Drilling Substrate Sheets

The idea with all of these materials is that they are easy to cut and drill. In most cases, ordinary
hand tools are all you need. Holes can be drilled with a hand drill, making these materials bet-
ter suited for robot projects involving young learners. (Give younger children pieces already
cut to size, to avoid having them handle a sharp knife.)
When cutting cardboard, foamboard, or corrugated plastic, bear in mind that small pieces
are inherently stiffer than larger ones. A 2- 4- foot sheet of corrugated plastic looks awfully

flimsy when you hold it, but cut down to the sizes you’ll most often use—4″ to 8″ round or
square— and suddenly the stuff is remarkably more rigid than you thought.
If, after cutting to size, you think the material is too thin to do its job, consider doubling up

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