Page 176 - Robot Builder's Bonanza

SELECTING LIGHTWEIGHT ROBOT MATERIALS 145

Core layer contributes to adding strength to
Foam, plastic, Thin overlay
paper the substrate. An example is shown in
material
Plastic, paper, Figure 14-1. The “sandwich” construction
metal, etc.
places a top and bottom layer (say, of thin
Figure 14-1 Substrates are constructed of sandwiching paper or plastic) with a very lightweight
layers of materials together, each layer reinforcing the other. core, such as Styrofoam. Individually each
For very lightweight substrates, a foam core is layered top and layer is quite flimsy, but when combined
bottom with a thick paper or plastic sheet.
the material is surprisingly strong and
sturdy.

CARDBOARD— HEAVY- DUTY, THAT IS
Cardboard is the most basic of all rapid prototyping substrates. While you could build a robot
base out of the cardboard of an ordinary shipping box, it’s a little too thin for the job (though
in a pinch you could always layer the cardboard to make it double- thickness).
Heavy- duty cardboard is available in thicknesses from 1/8″ to over 1/2″. You can find it in
larger sheets or simply cut up a used heavy- duty shipping box. Laminate several pieces of
cardboard to make it thicker and stiffer. “Criss- cross” the corrugation of the inner layers of the
cardboard for greater strength. Use a good paper glue or contact cement for a solid bond. Cut
with a sharp knife (be careful of your fingers!) or with any small fine- toothed saw.
An even heavier- duty cardboard uses a stiff honeycomb- like inner layer. It’s much more
expensive than ordinary cardboard, but when used properly it can hold over 50 pounds. You
can often find this type in packing materials for shipping very heavy objects, such as automo-
bile engines. For this, you want a hand or power saw; it’s too thick to be safely cut with a knife.

CORRUGATED PLASTIC

Corrugated plastic is a common staple in the sign- making biz. It’s used for temporary outdoor
signage, restaurant menu boards, that sort of thing. The plastic is composed of several layers,
all bonded together during manufacture. To give the material its strength, the inner core is
corrugated, like cardboard. Corrugated plastic comes in a variety of thicknesses, with 1/4″
being common. You can cut it with a knife or even a heavy- duty scissors. A quick mock- up or
prototype can be roughed out in minutes, and with simple tools.
Corrugated plastic gets its rigidity from its “fanfold” design. It’s meant to be used as a back-
ing for temporary outdoor signs, so it’s not particularly hardy. If you need a stiffer substrate,
you can use several layers of the plastic, sandwiching the layers at 90°. This orientation
increases the rigidity of the material.

FOAMBOARD

Foamboard (aka Foam Core, a brand name) is likewise a good candidate for quick prototypes.
This material is available at most craft and art supply stores and is constructed out of a foam
laminated on both sides with stiff paper. Most foamboard sheets are about 1/4″ thick, but
other thicknesses are available, too, from 2mm to half an inch. You can find foamboard in
colors at any art or craft supply store. Colored boards are more expensive, but you really only
need white.
Cut with a knife or small hobby saw. Make holes with a hand drill. Because the board is
laminated with paper, you can use any of a number of paper glues to try out different designs.

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