8. Building a Robot Body Out of ABS Plastic

Sometimes I'll create a robot extemporaneously. Sometimes I'll plan a robot precisely and completely in advance. However, most of the time I'll plan a little, build a little, and so on.

Mini-sumo robot plans, templates, and blueprints developed in Microsoft Visio.

For No.2, the project started with the drivetrain and wheels, the pencil holder, and the circuit boards. From there I needed to create a central frame to attach those pieces together.
I design my robot pieces in Microsoft Visio for three reasons:

• A drawing/drafting program (not a painting program) stores all of the information as exact shapes. They can be resized or altered at any time.
• The values of the dimensions can be entered exactly into Visio. For example, I can type 3/8-inch or 3 mm or even 3/8-3/32.
• If a 1:1 scale is selected, the plans can be printed out and they'll match the exact dimensions. That's useful for using them as paper templates during machining.

Looking at the blueprints for the No.2 robot, you may be able to see that I drafted items from different sides, depending on what needed to be machined or lined up to another part. For the most part, the center body created itself by simply putting the pieces together on the computer.

Machining a robot body out of solid ABS plastic on a mini milling machine.
The center body is made from a single solid piece of ABS plastic. ABS is fairly inexpensive, lightweight, tough, and yet much easier to machine than metal. ABS is available in black, which means it won't require any painting to absorb infrared.
I purchased a 12-inch x 12-inch x 1.5-inch thick plate of ABS from McMaster-Carr. Thicker pieces are available. You can sometimes find ABS plastic on an eBay auction, but not usually in this size. Chunks are cut out with a hack saw and then machined smoothly to size on a mini milling machine.
Before the grand finale, let's look above and below the robot...