06-06-2009 01:02 PM
Materials for your Robot
Materials for Your Robot
There are a variety of easy to use, easy to procure materials out there for building the frame of your robot. This tutorial will explain some of the robot materials I like to use.
Flat sheet plastics can be used to create a variety of robot frames. Everything from a flat deck to a fully enclosed chassis can be created. The use of tabs and slots to create 3D assemblies can make very professional looking frames. Corner blocks, like http://www.lynxmotion.com/Product.as...1&CategoryID=6 and http://www.budgetrobotics.com/shop/?...74111&cat=110& can be used to assemble parts at right angles. Standoffs can be useful to separate decks made of plastic.
Metals are generally lighter and thinner than a similar strength plastic. However, metals typically require more tooling, and burn through blades faster. L-angle metals can easily be cut and drilled to make sensor brackets, but be sure to use sharp bits -- the only thing a dull bit cuts is you!
Quite a bit of robot frame can be built with very little in tooling. A hacksaw and hand drill can go a long way. More than anything, the blade or bit will make the difference. A more advanced robot builder may find a scroll saw or a band saw to be extremely useful.
Here are some samples of things that can easily be made without much tooling. This first picture shows how a 1-1/2" long piece of 1/2"x5/16" aluminum L-angle, with 4 holes, can be used to make an IR bracket. Also, the picture includes a shot of one of my bots using Expanded PVC decks and standoffs.
With a little more work, we can make more advanced robots. My robot XR-B3, shown below, is made almost entirely of Expanded PVC with some Lynxmotion aluminum square bars. The middle deck is tied to the sides using tab and slot constructions. I constructed the entire bot using just a cheap dremel scroll saw, a hand drill, and a pair of tin snips and pliers to make the IR mounts seen on the side. Laying out the parts in a CAD program and then printing out and attaching them to your work piece makes cutout and drilling a breeze.
(A) Expanded PVC, or EPVC, is one of my most favorite materials. It is lightweight, fairly rigid, and comes in many colors. EPVC is very easy to drill, cut, and shape. XR-B3, shown above, is built entirely of EPVC. Unfortunately, it is one of the harder plastics to find, you will likely have to mail order it.
(B) Acrylic can be found in sheets, tubes, and many other shapes, as well as a variety of colors, both translucent and opaque. A sharp tool is necessary so as not to crack Acrylic when drilling or cutting. Acrylic can be brittle and shatter. Available in most home stores in 1/8" or 1/4" thickness sheets, other shapes will likely be special order.
(C) Expanded Polyethylene can be found in many different shapes. Again, a special order item typically. Easy to drill, cut and shape, and low cost.
(D, F) Lexan is a bit tougher than EPVC. It is virtually unbreakable. Typically sold in sheets of 1/8" or 1/4" thickness, in either clear or opaque black. Available in most home stores. Specialty stores such as McMaster-Carr sell lexan in extruded forms like L-angle.
(E) Thin sheets of lexan (0.020"-0.040") can be used for forming body covers. This material is used for RC car bodies, and can be found at hobby stores in fairly large sheets of about 12"x16" for under $10. Because it is clear, you can paint the inside and the color shines through quite nicely. Be sure to get paint specifically formulated for lexan (available at your hobby store), and to do all the bending before painting.
ABS is another plastic with strength in between PVC and Lexan. Typically found in black or white sheets.
While there are a wide variety of metals available today, I will only discuss the easiest to find and machine. Aluminum Angle is available in various grades and alloys, but the stuff you find at a hardware store will do most people fine. Angle and flat stock can be used to create a variety of brackets and frames. Easily drilled, easily cut with a hacksaw.
Aluminum roofing flashing or thin aluminum sheeting can be found in home centers at fairly low cost. Flashing can be cut with tin snips, thin sheeting can be cut with a hacksaw, scroll saw or band saw.
Zip ties, double sided tape, and velcro can be used for attaching pretty much anything. Foamboard can be used for prototyping smaller robot chassis (which can later be cut from sheet goods, or even just use the foamboard parts if the robot is kept light enough). You can never have too much of these materials.