Class11_1

Today: • Technical drawing using CAD

DP…questions?

Reminders: DatesDesign demonstration is 3.5 weeks from today.

It goes fast! Remember advice of previous classes: “Leave lots of time for testing.”

Questions?

CAD

• CAD is a tool to help you make technical drawings; you must make the drawings

• Using CAD is not the same as doing design

CAD

• Can be highly accurate• Allows easy repetition and revision• Provides input to other analyses and

manufacturing programs

CAD

• Drawings are full scale (true size units)• Objects (such as lines) have numerically

defined properties, such as end-point coordinates

CAD

• The drawing is more than its appearance—it is a numerical description of the geometry (example: lines do not just appear to connect, they share the same end point coordinates)

CAD

Bottom line….

A CAD file is a NUMERICAL DATABASE describing your part. It is not a picture. Need to adopt this mindset when making a CAD drawing.

AutoCAD

• New users beware: in AutoCAD there are usually about 5 ways to accomplish the same thing; this can be confusing at first

• Tip: learn to use the command line and depend less on the mouse

• Tip: read the help files because there are lots of details and tricks to learn

Let’s take a look at AutoCAD

• Graphics area• Command line• Toolbars• Pull down menus• Dialog boxes• Status bar and drawing aids• Model vs. layout space

AutoCAD• The free student version is available from

Autodesk

• We will use the AutoCAD Classic interface.

AutoCAD

• Draw commands• Draw commands create objects• Remember: you are creating a numeric

object, not just lines on a screen…• Many ways to accomplish the same thing

AutoCAD

• Help files• Spacebar same as enter• Hit ESC to cancel current command• Drawing aid: ortho

AutoCAD

• Ways to specify coordinate points:– Pick (interactive with mouse)– Absolute X,Y– Relative rectangular @X,Y– Relative polar @distance<angle– Direct distance

Exercise 1

• Draw the following lines using the procedure suggested…

Circles and Arcs

• Can be drawn with a variety of options• Notice the use of the Command Line• Examples

– Center, radius– Center, diameter– Two points – Tangent, tangent, radius

AutoCAD

• Modify commands• Selection sets • Oops• Undo

Exercise 2

• Draw a bunch of circles• Try selection set methods • Experiment with Erase• Remember: use Esc to abort a command• Experiment with Oops and Undo

AutoCAD

• Setting up drawings• Limits• Zoom window, zoom previous• Zoom all

Drawing aids

• ORTHO to restrict only horz/vert lines• OBJECT SNAP enables the cursor to

“snap” to existing object features, such as end points

• Types of object features to snap to• Running OSNAP• Command line OSNAP

More AutoCAD functionality

• Construction line type• More Modify commands: Fillet, Offset• More Modify commands: Mirror

Exercise

• Draw top item on the handout• Do not include dimensions• If you already know how to do this, help a

person sitting near you.

More AutoCAD: Layers

• Layers• Tip: the availability of layers is a great

feature of CAD…learn to use layers effectively (use lots of them)

• Do not draw on the 0 layer or the defpoints layers. These have special properties and should be reserved for that use.

Example of using layers

• Set up layers in preparation for drawing Layers:– Part, black, continuous– Construction, light grey, continuous– Center line, black, centerline style