Post on 05-Apr-2020
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Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Session 3 : Orthographic Projection
Represent an object with drawings
Real world is 3D whereas paper is 2D
3D projection 2D
Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Projection
Lines of sight(L.S.)
Observer
Object Plane of projection(= drawing paper)
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Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Types of projection
Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Perspective vs. Parallel projections
Perspective Parallel
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Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Parallel projection
Orthographic Oblique
L.S. perpendicular to plane L.S. oblique to plane
Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Orthographic projection
Multiview Axonometric
Face align with plane Edge align with plane:Isometric, Dimetric, Trimetric.
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Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
• Third-angle projection- Object is assumed to bebehind the image plane
- Line of sight: image plane object
- View is formed by projectingback to the image plane
- used in U.S.A., Ca, UK, TH,etc.
3rd Angle projection
Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
1st Angle projection
• First-angle projection- Object is assumed to bein front of the image plane
- Line of sight: object image plane
- View is formed by projectingthrough object and onto theimage plane
- used in other countries
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Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
1st and 3rd Angle projections
1st angle 3rd angle
Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Views of objects
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Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Six views of an object
Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Plane of projection & Lines of sight
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Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Projection of lines
Projection of line shows a point on
plane
Projection of line shows a true length
on plane
Projection of line shows a foreshortened
on plane
Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Projection of planes
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Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Projecting onto views
Note: Numbers of visible points in a givenview are placed outside the corners.
Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Relationship of orthogonal views
Front
Top
Side
Depth
Width
Height
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Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
3rd angle projection
Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Methods of projection between views
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Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Choosing numbers of views
3 Views:top, front, and side
2 Views:top, and front
1 View:top (or front) &
diameters
Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Hidden lines practices (I)
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Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Hidden lines practices (II)
Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Center-line practicesSmall dashes cross at the center
Extends past edge of object 8 mm.
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Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Precedence of lines
Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Good & poor techniques
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Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Tangency v.s. Edges
Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Representation of non-tangency
Front
Top
Side
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Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Representation of tangency
Front
Top
Side
Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Revolution conventions (I)
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Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Revolution conventions (II)
Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Don’t do.
Redundant Unnatural
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Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Don’t do.
Faculty of Engineering, TU ME 111 Engineering Graphics TEP & TEPE: International Programmes of Engineering
Example