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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.
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Questions about DP?
The lab is open.
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Define the problem
Specify product requirements
Invent alternatives
Evaluate the alternatives
Engineer the details / analyze performance
Test prototypes
Report complete product description
Model of the Design Process
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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”!
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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.
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Engineering graphics (technical drawing)
• Technical drawings are an important method of communication among engineers.
• Introduction to the nature and purpose of technical drawings
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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.
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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.
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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).
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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
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Typical “projections”
• Orthographic projection (sometimes called “multiview” drawings) (the fundamental engineering drawing)
• Isometric projection (a pictorial view)• Oblique projection (another pictorial view)
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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.
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Example of the process…
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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
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Draw an isometric view (single pictorial view)
• Use construction lines• Pay particular attention to proportions• Remember, each front edge at 30 degree
angle
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That’s all for today!
Remember: Computer model due Tuesday.