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Dr Simin Nasseri Southern Polytechnic State University 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 7 Engineering Graphics I Dr Simin Nasseri Southern Polytechnic State University

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Dr Simin Nasseri Southern Polytechnic State University 2 1.Sketching is an important method of quickly communicating design ideas. 2.Sketching is a way of thinking as it is a method of recording ideas and communicating to others. 3.Most new designs are first recorded using design sketches.

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Dr Simin Nasseri Southern Polytechnic State University 3 Figure 7.1 3 Methods for creating drawings: Sketches Using T- squares, triangles, etc. CAD produced drawings

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Dr Simin Nasseri Southern Polytechnic State University 4 Figure 7.3 A technical sketch: Producing a rough, preliminary drawing representing a product or structure.

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Dr Simin Nasseri Southern Polytechnic State University 5 Figure 7.26 Sketching the idea (ideation sketch) Subsequent document sketch

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Dr Simin Nasseri Southern Polytechnic State University 6 Figure 7.4 Multi-view sketch: Good for someone who understands technical drawings

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Dr Simin Nasseri Southern Polytechnic State University 7 Figure 7.5 Pictorial view: Good for communicating the design. Suitable for nontechnical people.

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Dr Simin Nasseri Southern Polytechnic State University 8 Figure 7.8 Grid papers: Square paper ( 4 to 10 lines per inch) Isometric grid paper Perspective grid paper: To create pictorial sketches

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Dr Simin Nasseri Southern Polytechnic State University 9 Figure 7.9

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Dr Simin Nasseri Southern Polytechnic State University 10 Figure 7.10 The line is built up from a sequence of 2, 3 or more passes with a pencil.

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Dr Simin Nasseri Southern Polytechnic State University 11 Figure 7.11

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Dr Simin Nasseri Southern Polytechnic State University 12 Figure 7.12 Hold your pencil correctly, and have a relaxed grip. Use a strip of paper to draw lines parallel to the edges of the paper.

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Dr Simin Nasseri Southern Polytechnic State University 13 Figure 7.13 How to draw a circle: Each side of the square is equal to the diameter of the circle. Draw the diagonals and mark the midpoints. On the diagonals mark 2/3 of the distance between the center and each corner. Connect all the points. An alternative method

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Dr Simin Nasseri Southern Polytechnic State University 14 Figure 7.14 Examples of poorly drawn circles (with flat arcs and sharp corners)

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Dr Simin Nasseri Southern Polytechnic State University 15 Figure 7.15 Contour sketch: Observe the outline of the object while sketching, Improves your sketching ability.

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Dr Simin Nasseri Southern Polytechnic State University 16 Practice: Look at an object and try to sketch it upside down. (Sketch the outline of the object by concentrating on the geometric forms not the names of the parts).

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Dr Simin Nasseri Southern Polytechnic State University 17 Sketching techniques: 1- Proportion is important. It is the ratio between any two dimensions of an object. Figure 7.22

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Dr Simin Nasseri Southern Polytechnic State University 18 Figure 7.18 2- Draw the bounding box. 1- Consider the correct proportion. 3- Draw the construction lines. These are every light thin lines representing the details of the object. 4- Finish the sketch with darker lines.

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Dr Simin Nasseri Southern Polytechnic State University 19 Figure 7.19 You can use construction line to find the center of squares or rectangles.

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Dr Simin Nasseri Southern Polytechnic State University 20 Figure 7.21 Sketching identically proportioned squares

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Dr Simin Nasseri Southern Polytechnic State University 21 Figure 7.23 Grid paper is used to scale an object.

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Dr Simin Nasseri Southern Polytechnic State University 22 Figure 7.24 Sketching at a distance: 1.Stand at a distance, 2.Hold a pencil at arm’s length in front of you, 3.Align the tip of the pencil with one edge of a feature, 4.Mark the length of the feature with your thumb, 5.Translate the same length to your sketch. 6.Repeat this for other lengths. Don’t change your position.

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Dr Simin Nasseri Southern Polytechnic State University 23 Figure 7.28 Most common types of projections: Isometric

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Dr Simin Nasseri Southern Polytechnic State University 24 Most common types of projections: 1.Multiview (Showing 2 dimensions) 2.Pictorial (Showing 3 dimensions) OR Most common types of projections: 1.Parallel 2.Perspective projections

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Dr Simin Nasseri Southern Polytechnic State University 25 Figure 7.29 Perspective projection Although it is more realistic, it is for larger objects like a house or bridge. Is this projection multiview or pictorial? Is it a parallel projection or perspective?

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Dr Simin Nasseri Southern Polytechnic State University 26 Figure 7.30 Isometric projection: A type of parallel projection that represents all 3 dimensions in one image. Practice: Draw a chair.

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Dr Simin Nasseri Southern Polytechnic State University 27 Figure 7.31

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Dr Simin Nasseri Southern Polytechnic State University 28 Figure 7.32 Isometric representations of circles

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Dr Simin Nasseri Southern Polytechnic State University 29 Figure 7.33 Practice: Draw a circle on profile and top planes.

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Dr Simin Nasseri Southern Polytechnic State University 30 Figure 7.34

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Dr Simin Nasseri Southern Polytechnic State University 31 Practice: 2- Sketch the isometric semicircle, shown here. 1- Sketch this cylinder using the method you learned:

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Dr Simin Nasseri Southern Polytechnic State University 32 Figure 7.35 Practice: Rotate the object and sketch it again.

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Dr Simin Nasseri Southern Polytechnic State University 33 Figure 7.36 Isometric sketches of common objects.

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Dr Simin Nasseri Southern Polytechnic State University 34 Figure 7.52 Use a piece of scrap paper and mark one half of the major axis (AC) and one half of the minor axis (AB). Place A on the center and mark two points representing C and two points representing B (draw major and minor axes). Place C on the minor axis and hold B on the minor axis at any time, then place a mark at point A. Repeat this and connect all the points.

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