What Next? 269Experiment 32: A Little Robot Cartplywood to complete the two little robotics projects here (ideally, the kind of
thin, high-quality plywood sold by hobby stores) but I recommend something
that looks better and is easier to work with: ABS plastic. Before you start on the
robotic cart, you may want to check the section “Fundamentals: All about ABS.”
FundAmentAls
All about ABS
Unless you think the steampunk movement isn’t going back far enough, you
probably don’t want your autonomous robot cart to resemble a relic from
before the 1800s. Therefore, wood may not be the best construction material.
Metal can look nice, but is not easy to work with. For quick results that have a
twentieth-century look (maybe even a 21st-century look), plastic is the obvious
choice, and I feel that ABS is the best type of plastic to use, because it provides
such quick, easy results. ABS stands for “acrylonitrile butadiene styrene.” Lego®
blocks are made of ABS. Car-stereo installers and model-railroad buffs use it.
You can use it, too. You can saw it, drill it, sand it, whittle it, and drive screws into
it, and it won’t warp, split, or splinter. It’s washable, doesn’t need to be painted,
and will last almost forever.
Delrin is another type of plastic, but tends to cost more and is a little tougher
to drill and cut. It’s a matter of personal preference. ABS machines fairly well,
but when you drill it, for example, it can “catch” on the bit and the piece will
spin with the bit due to the way that plastic chips off with the bit. Delrin is self-
lubricating and has better melting properties under the heat of machining, so it
drills and cuts much more cleanly and easily than ABS.Where to find ABS
Pieces of ABS a couple of feet square are available from online sources such as
http://hobbylinc.com or estreetplastics (an eBay store), but you’ll save money if
you can truck on down to your nearest plastic supply house and buy it like ply-
wood, in sheets measuring 4 by 8 feet. To discover whether you have a nearby
plastic supply house, search for “plastic supply” in your yellow pages or Google
Local.
Piedmont Regal Plastics has many supply centers around the nation, but you’ll
have to collect it yourself, and they may not be willing to cut small pieces. You
can check online at http://www.piedmontplastics.com for their locations.
Stock colors of ABS include black, white, and “natural,” which is beige. Sheets
usually are textured on one side, which is the side that should face outward, as
it is more scratch-resistant than the smooth side.
Because you won’t be adding paint or other finishes, you’ll have to be careful
not to scuff the plastic or scratch it while working. Clean your bench thoroughly
before you begin, taking special care to remove any metal particles, which tend
to become embedded in the plastic. Use wooden shims in the jaws of your vise,
and avoid resting the plastic accidentally on any sharp tools or screws. Working
with ABS requires a clean environment and a very gentle touch.