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.

Questions about DP? The lab is open.

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

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”!

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.

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

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.

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.

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).

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

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

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.

Example of the process…

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

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

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