1. Class 9_2 Next stage in design process: Testing
Intro to engineering drawing
Computer model assignment due next Tuesday
Extra office hours Friday morning, 10-noon.

2. Questions about DP?
The lab is open.

3. Model of the Design Process
Define the problem
Specify product requirements
Invent alternatives
Evaluate the alternatives
Engineer the details / analyze performance
Test prototypes
Report complete product description

4. Testing
Crucial part of design, because the problems are complex and the solutions not certain
Often start with simple prototypes
Design the tests carefully so that the results will be useful
Keep records
Be ready to “iterate”!

5. Testing Testing is not the same as practicing. Test systematically.
Change one variable at a time, in uniform steps, hold all other variables constant.
Record the results carefully.

6. Engineering graphics (technical drawing)
Technical drawings are an important method of communication among engineers.
Introduction to the nature and purpose of technical drawings

7. Nature and purpose of technical drawings
Technical drawings are formal, not artistic, follow we ll-defined rules/conventions.
Composed of simple lines, no color, no shading, no vanishing perspective, no extraneous detail, no artistic interpretation.

8. Nature and purpose of technical drawings
Primary purpose is to communicate detailed information about the geometry of a design.
Used as a basis for manufacture.
Aid in designing a device by clarifying the geometric relationships of the parts.
Communicates ideas about the design to others—other engineers, manufacturer, customer, maintenance staff, parts inventory staff, etc.
Starting point for other types of analysis, such as FEA stress, etc.

9. Nature and purpose of technical drawings
Done by hand (sketches) or with drawing aids (squares, triangles…), or most often today, with the help of a computer (Computer aided drawing, CAD).

10. Why engineers need to be able to make technical drawing sketches
Helps you develop your ideas and is an aid to problem solving 
Informal communication among colleagues
Quick communication to shop
Communication to drafting staff
Understanding the principles helps understand formal drawings

11. Typical “projections”
 Orthographic projection (sometimes called “multiview” drawings) (the fundamental engineering drawing)
Isometric projection (a pictorial view)
Oblique projection (another pictorial view)

15. Stages in making a sketch
Block-out the outline with “construction lines”
Block-out the major features
Refine shapes
Darken part lines
Tips: Use construction lines liberally, draw big (use entire page), pay attention to proportions, relax and practice.

16. Example of the process…

17. In-class work: Use paper provided and a pencil to practice drawing.
Draw an orthographic projection (three views in proper relationship)
Start with construction lines to block out all views
Draw big, keep proportions
Fill in details with heavier lines

20. Draw an isometric view (single pictorial view)
Use construction lines
Pay particular attention to proportions
Remember, each front edge at 30 degree angle

23. That’s all for today!
Remember: Computer model due Tuesday.