Engineering graphics introduction

1. ENGINEERING GRAPHICS
Engineering is a creative profession:
… engineers create what has never been’
Why graphics ?
Why engineering ?
… a universal language
… used in creation and communication
‘scientists explore what is …

2. But graphic images from 15,000-18,000 BC
communicate very effectively today
Red ochre cave painting
Vallon-Pont-d'Arc, France

3. A universal graphic language?
Egyptian hieroglyphs were based on
recognisable graphic symbols

4. Chinese characters became much
more abstract

5. Many Western languages use standard
symbols,
but not in a universal way …
Hello
Bon Jour
Guten Tag
G’day
...

6. Sketches Leonardo da Vinci (1452-1519)
Perspective
projection
Parallel
projection
We will study
‘orthographic’ projection
systems in detail

7. a printer
Imagine trying to
describe this
printer, precisely,
using verbal
communication

8. Orthographic projection
• Multi-view drawings provide the most accurate
description of 3D objects and structures for
engineering, manufacturing, and construction
requirements

9. Classical Projections

10. Orthographic Projection
• The word Orthographic means 'to draw at
right angles'. Hence orthographic
projection is a means of visualising an
object by projecting its edges at right
angles onto the projection plane.
• In practice, orthographic projection uses
two main planes, called the principal
planes of projection or planes of reference

11. Orthographic Projection
Projectors are orthogonal (90°) to projection
surface

12. Orthographic Projection
In engineering, there are two systems of
projection:
– First Angle Projection – Europe, Asia and
former European colonies in Africa and parts
of Australia
– Third Angle Projection – Used in the USA and
Canada, in Africa where American
development is taking place and parts of
Australia

13. First Angle Projection
• Fist Angle Projection - object positioned in space
in the First Quadrant.
• View on the vertical plane - ELEVATION
• View on the horizontal plane - PLAN
• To obtain the views as they would appear on a
sheet of paper, the horizontal plane is opened
out about the intersection of the planes. The line
of intersection is called the XY line, ground line
or folding line.

15. Perspective Projection

16. Parallel Projection

19. Glass projection box
End elevation
Plan
Elevation

20. YY line or fold line
Vertical
plane
End vertical
plane
Horizontal plane
XY lines or fold lines

21. Vertical
plane
End vertical
plane
Horizontal plane
YY line of fold line
XY lines or fold lines
Elevation
End elevation
Plan

22. End
vertical
plane
Vertical plane
Horizontal plane

27. Front Elevation
End Elevation
(Left)
End Elevation
(Right)
Plan View

28. First Angle Plan View
Front Elevation
End Elevation
(Left)
End Elevation
(Right)

29. Advantages and Disadvantages
• Preserves both distances and angles
– Shapes preserved
– Can be used for measurements
• Building plans
• Manuals
• Cannot see what object really looks like
because many surfaces hidden from view
– Often we add the isometric (3D)