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Dr Simin NasseriDr Simin NasseriSouthern Polytechnic State UniversitySouthern Polytechnic State University
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chapter 7
Engineering Graphics IDr Simin Nasseri
Southern Polytechnic State University
Dr Simin NasseriDr Simin NasseriSouthern Polytechnic State UniversitySouthern Polytechnic State University
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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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Figure 7.1
3 Methods for creating drawings:
Sketches Using T-squares,
triangles, etc.
CAD produced drawings
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Figure 7.3
A technical sketch:Producing a rough, preliminary drawing representing a product or structure.
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Figure 7.26
Sketching the idea (ideation sketch)
Subsequent document sketch
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Figure 7.4
Multi-view sketch:Good for someone who understands technical drawings
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Figure 7.5
Pictorial view:Good for communicating the design.
Suitable for nontechnical people.
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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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Figure 7.9
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Figure 7.10
The line is built up from a sequence of 2, 3 or more passes with a pencil.
Dr Simin NasseriDr Simin NasseriSouthern Polytechnic State UniversitySouthern Polytechnic State University
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Figure 7.11
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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.
Dr Simin NasseriDr Simin NasseriSouthern Polytechnic State UniversitySouthern Polytechnic State University
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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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Figure 7.14
Examples of poorly drawn circles (with flat arcs and sharp corners)
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Figure 7.15
Contour sketch:Observe the outline of the object while sketching,Improves your sketching ability.
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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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Sketching techniques:
1- Proportion is important. It is the ratio between any two dimensions of an object.
Figure 7.22
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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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Figure 7.19
You can use construction line to find the center of squares or rectangles.
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Figure 7.21
Sketching identically proportioned squares
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Figure 7.23
Grid paper is used to scale an object.
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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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Figure 7.28
Most common types of projections:
Isometric
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Most common types of projections:1. Multiview (Showing 2 dimensions)2. Pictorial (Showing 3 dimensions)
OR
Most common types of projections:1. Parallel2. Perspective projections
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Figure 7.29
Perspective projectionAlthough 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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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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Figure 7.31
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Figure 7.32
Isometric representations of circles
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Figure 7.33
Practice:Draw a circle on profile and top planes.
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Figure 7.34
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Practice:
2- Sketch the isometric semicircle, shown here.
1- Sketch this cylinder using the method you learned:
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Figure 7.35
Practice: Rotate the object and sketch it again.
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Figure 7.36
Isometric sketches of common objects.
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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.
