Lecture 1 W2 engineering drawing

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LECTURE 01

IMPORTANCE OFENGINEERING DRAWINGS

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Why learn ED?

Engineering graphics/drawings

provide means to expression of

thoughts and concepts

involving geometrical shapes

and design between the

designers (engineers) and

fabricators (vendors). Drawing

is a tool to communicate ideas


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What are ED?

Engineering graphics/drawings are important for:

Visual communication

between

Draftsmen and engineers

/ other professionals

Designers / architects and

manufacturers /

contractors

End-users and

sales/support services

Transmission of coding

technique


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Relevancy of ED

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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Example of drawing

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Bearing


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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 ToolsFor 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

Flexible 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 solidmodeling)

MS Visio (2D with built-in

blocks/libraries)


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ED 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

Scales are 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 - Metric & Imperial

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 andarcs

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

Documents

Lecture 1 W2 engineering drawing