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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