ME En 112 Engineering Drawing with CAD Applications

Fundamentals of Graphic Communication

Chapter 6. Pictorial Drawings

Objective: We learn how to create 3 types of pictorial drawing (See Fig. 6.2)
 
  • Isometric Drawings (6.1 & 6.2) è Theory of isometric projection (Fig 6.9), Position of isometric axes (Fig 6.9), Isometric and Non-isometric lines and planes (Fig. 6.10~6.12), Standards for hidden lines, center lines, and dimensioning (Fig. 6.13~6.15), Isometric drawing construction (Fig. 6.17~6.42)
  • Oblique Drawings (6.3) è Oblique projection theory & Classification (Fig. 6.46~6.50), Object orientation rules (Fig. 6.51~6.55), Dimensioning (Fig. 6.65), Oblique drawing construction ( Fig. 6.56~6.64)
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  • Perspective Drawings (6.4~6.7) è Perspective vs. orthogonal (Fig. 6.69), Vanishing point position and ground line position (Fig. 6.17 & 6.73), Classification of perspective drawing (Fig. 6.74), Perspective drawing variables selection (6.7)
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    6.2
    • See the difference among Isometric, Dimetric, and Trimetric (Fig. 6.3)
    • Depending on where you place isometric axes, you get different views (Use most effective position to meet the need) (Fig. 6.9)
    • Isometric lines appear in true length; non-isometric lines cannot be measured directly. What makes a plane an isometric plane or a non-isometric plane? (See Fig 6.10~6.12).
    • In isometric drawings, hidden lines are omitted unless they are absolutely necessary to completely describe the object. Centerlines are drawn only for showing symmetry or for dimensioning. Normally centerlines are not shown. (Fig. 6.13 and 6.14)
    • Dimensioned isometric drawings used for production purposes must conform to ANSI standards. (Fig. 6.15 and Left column of page 377) 
    • Isometric drawing construction examples. In class we go over Figures 6.17, 6.20 and 6.22, but you should take a look at Figures 6.17 through 6.42 and know where you can find instructions when you tackle worksheets related to this topic. 
  • Oblique Drawings (6.3)
    • 6.3
    • Oblique projection is a form of parallel projection in which the projectors are parallel to each other but are not perpendicular to the projection plane. The actual angle that the projectors make with the plane of projection is not fixed. But 30 to 60 degrees are recommended. (Fig. 6.47)
    • We have cavalier oblique, cabinet oblique, and general oblique. (Fig. 6.50)
    • In oblique projection, first, the object face that is placed parallel to the frontal plane will be drawn true size and shape. Hence, the most complex features must be parallel to the frontal plane. Second, the longest dimension of an object should be parallel to the frontal plane. If there is a conflict, the first rule takes precedence. (Fig. 6.51~6.55)
    • In oblique drawings, dimensions lie in the plane of the surface to which they apply, and unidirectional text placement is used. (Fig. 6.65)
    • Oblique drawing construction examples. In class we cover methods described in Fig. 6.56, 6.57, and 6.60
    6.4
    • The most realistic representation of 3D objects on 2D media. (Fig 6.66, 6.69)
    6.5
    • Some terms you want to know: horizon line, ground line, station point, picture plane, and vanishing point. (Fig. 6.69)
    • VP position, horizon line, and ground line, in combination, create different perspective views. (Fig. 6.17 & 6.73)
    6.6
    • There are one-, two-, and three-point perspective drawings. See Fig. 6.74 to see the difference among the 3 types.
    6.7 The variables in perspective drawings are:
    1. Distance of object from picture plane
    2. Position for station point
    3. Position of ground line relative to horizon. 
    4. Number of vanishing points