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LECTURE 01

IMPORTANCE OFENGINEERING GRAPHICS

CAB 1052

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Why learn EG?

Engineering graphics provide means to

expression of thoughts and concepts

involving geometrical shapes and designbetween the designers (engineers) and

fabricators (vendors).

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What are EG?

Engineering graphics are important for:

Visual communication between

Draftsmen and engineers / otherprofessionals

Designers / architects and manufacturers /

contractors

End-users and sales/support services

Transmission of coding technique

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Relevancy of EG

Every engineer should be able to:

Describe ideas and present them to other

professionals through engineering graphics Read and understand graphics prepared by

others

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Three Methods of Communication

THREE (3) methods of communicating the

graphics language:

Free hand sketches

Manual drafting with hand-held instruments

Computer-aided drafting/design (CAD)

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Manual Drafting Tools

For manual drafting and/or freehand

sketches, the following may be required:

Board / table

Media (paper: plain, graph)

Utensils

Pencils / pens

Eraser

T-squares and triangles (set squares)

Compass and dividers

Protractor

French curve

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CAD Software

Among the popular CAD software used intechnical drawings/draftings are:

AutoCAD (2D, 3D, solid modeling)

Mechanical Desktop (3D, solid modeling)

Inventor (advanced solid modeling)

MS Visio (2D with built-in blocks/libraries)

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EG Outputs

The outputs are in the forms of:

Documentation (step-by-step procedure)

Technical drawings

the shape, size, location and other features

of the object(s)

Surface finish, color, assembly or fabrication

methods

Standards and conventions (layout /

template)

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Two component of graphics

Showing the shape of an object and otherinformation requires TWO (2) fundamental

components of graphics:

Lines represents edges, contour and/or

surfaces of objects

Lettering represents symbols, sizes and notes

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Scale

Scalesare graduated measuringinstruments

Drawing scales refer to ratio between size

of drawing to actual size of object scale ratio 1:50 means actual object is 50

times larger than drawing object

scale ratio 2:1 means actual object is half

the size of the drawing object

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Scale (Reaction Vessel Example)

Model

Actual

Scale

1:100

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Units

Engineering

Millimeters (mm)

Inches (in.)

Architectural

Feet ( ' ) and inches ( " )

TWO (2) major unit conventions commonlyused in drawing are:

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Units

Some examples to differentiate the units:

Millimeters

Inches

Architectural

2

2

2"

2.1

2.10

2 1/2"

0.021

.021

2'-2 1/2"

Note:

A zero is required to the left (but not to the right) ofdecimal point for mm. For inches, vice versa.

Symbols are not required for mm and in.

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Dimensions

Linear dimensions horizontal and vertical lines

Angular dimension angles

Diameter places a diameter dimension on circles

Radius

places a radius dimension on circles and arcsOrdinate also called datum dimensions that measure aperpendicular distance from an origin. The origin can bespecified by the user

Aligned dimensions which lines neither horizontal or vertical

Dimensions are used to indicate the length,radius (diameter) and angle of an object.

Some common terminologies as used in

standard drawing conventions and practices

are:

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Dimensions