IMPORTANCE OF ENGINEERING DRAWING
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IMPORTANCE OFENGINEERING DRAWING
CCB 1052
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CAB 1052
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Why learn ED?
Engineering graphics 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 EG?
Engineering graphics are important for:
Visual communicationbetween
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 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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Example of drawing
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Three Methods of Communication
THREE (3) methods of communicating the
graphics language:
Free handsketches Manual drafting with hand-held instruments
Computer-aideddrafting/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
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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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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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Scale
Scalesare graduated measuringinstruments
Drawing scalesrefer to ratio between size
of drawing to actual size of object scale ratio 1:50means actual object is 50
times larger than drawing object
scale ratio 2:1means 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 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
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Chapter 2
part a
TECHNICAL SKETCHING
CCB 1052
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Sketching Techniques
Freehand
Mechanical (drawing instruments)Digital (Computer Aided)
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Proportions
Sketches should be proportional. Dont drawa square that looks like a rectangle or a circle
like an ellipse. The common technique of
sketching is:
Sketch lightly
Check the proportions (between actual & drawing)
Make correction (erase as necessary)
Darken lines (final drawing)
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Proportions
Fig. 4-4
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Class Exercise
The correct proportion technique:
1) Concentrate on the overall object size
2) Followed by the medium sized parts
3) Then the smaller ones
4) Darken lines & erase as necessary
Boundary boxrepresent the outer dimensional limits
of the feature being drawn