Page 189 - Robot Builder's Bonanza

158 DRAFTING BOTS WITH COMPUTER- AIDED DESIGN

is used to denote the origin (the start point in virtual space) of the drawing. With most CAD
programs the origin is the lower- left corner of the drawing and is denoted as 0,0. The first
digit is the X axis; the second digit is the Y axis.

File Formats for Vector Graphics

You’re probably familiar with GIF, JPG, and PNG graphics files. These are all bitmap file
formats and typical of images you see on Web sites. Each is a different data format and, by
convention, the specific format is used as the filename extension— a file named myrobot.jpg
is a JPG bitmap of someone’s robot.
Likewise, vector graphics have their own file formats. As many were created for a special
purpose or graphics program, they tend to be unique to themselves and often are not compat-
ible with one another (you can sometimes use a converter program to exchange one format
for another, but the results can leave much to be desired).
Of the varied vector graphics formats, these that follow are the most common, and the
ones you’ll likely work with and share with others.

• SVG— Scalable Vector Graphics, now the uber- standard for vector- based images, and sup-
ported by Wikipedia. This is Inkscape’s default file format.
• EPS— Encapsulated PostScript is an interchange format promoted by Adobe. It contains
definitions of the graphic elements as PostScript command codes, plus (usually) a
medium- resolution bitmap for use by those programs that can only import a bitmap. Pro-
grams have varying support for EPS, and some— like Inkscape— need additional plugins to
understand the format.
• AI— The native file format for Adobe Illustrator, AI is one of the premier commercial vector
graphics applications. Saving and sharing this format is acceptable as long as everyone has
Illustrator and, better yet, similar versions. Otherwise, use SVG.
• DXF— The Drawing Exchange Format is most commonly found on CAD programs and
was originally developed by AutoDesk to allow AutoCad to share its 2D files with other
applications. It’s now become a de facto standard for all CAD apps.
• DWG— Like DXG, the Drawing format is used for interchange with CAD programs and is
primarily intended for 3D graphics. It’s not as widely supported as DXF.

File formats common in some 3D CAD programs include SAT, STEP, IGES, and INV. Not
all CAD programs can open them. If you share your designs with others, be sure everyone has
the same CAD program or can open the files without significant loss of information.

Using Laser- Cutting Services

See that cutting and drilling template in Figure 15-4? Because it’s made to exact scale, you
could use the drawing to have your robot base professionally produced with a laser cutter.
Laser cutters use a high- intensity pencil- thin light beam to make precision holes and cuts in
wood, plastics, and even some metals.
Cost varies depending on the amount being cut and the type and thickness of the material,
but it’s less expensive than most people think. It’s a good alternative if you have a complex
design and need the precision that hand- cut parts can’t provide.

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