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How We Represent Objects

Through Drawing

Working Document Linguistic review 29-09-07

Technical Drawing –

Part of the Design Process

�Before something can be produced, it

needs to be imagined by someone.

�A drawing is a graphic representation

of the real thing or idea to be

produced.

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The Design Process (Giesecke et al. Technical Drawing, 12th edition. 2000)

1. Problem Identification

2. Concepts and Ideas

3. Compromise solutions

4. Models and/or Prototypes

5. Working drawings for production

Technical Drawings vs. Sketching

�Technical Drawing

�Used to express technical ideas with precision

�Technical Sketching (Diagram)

�A freehand expression of graphic language

�Tool to quickly express technical ideas.

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� [MATHEMATICS] the operation by which we make all points on a given surface correspond to a point on another surface;

�The action of projecting an image on a screen.

Projections

To project:

PROJECTIONS

PARALLEL PROJECTIONS

ORTHOGRAPHIC PROJECTIONS

CONICAL PROJECTIONS

OBLIQUE PROJECTIONS

ISOMETRIC

MULTI-VIEW

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The Description of Forms

Behind every drawing of an object is space relationship involving four imaginary things:

• an object;

• a plane of projection;

• an observer (the station point);

• projectors – lines of sight.

Some Types of Projections

ISOMETRIC

PROJECTIONS

CONICAL PROJECTIONS

OBLIQUE PROJECTIONS

MULTI-VIEW

PARALLEL PROJECTIONS

ORTHOGRAPHIC PROJECTIONS

Let’s look here first

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Conical projections

� In this type of drawing, the observer is relatively close to the projection plane.

�The lines of vision thus form a cone directed towards the observer’s eye.

�In conical projections, the edges

which are closer to an observer,

are larger compared to the edges

which are farther

�When drawing conical projections,

use at least 2 vanishing points

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Types of projections

ISOMETRIC

PROJECTIONS

CONICAL PROJECTIONS

OBLIQUE PROJECTIONS

MULTI-VIEW

PARALLEL PROJECTIONS

ORTHOGRAPHIC PROJECTIONS

Let’s look here next

Parallel projections

In this type of drawing, the observer is infinitely far away. The lines of vision then appear to be parallel.

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Types of projections

ISOMETRIC

PROJECTIONS

CONICAL PROJECTIONS

OBLIQUE PROJECTIONS

MULTI-VIEW

PARALLEL PROJECTIONS

ORTHOGRAPHIC PROJECTIONS Let’s look here next

Orthographic

parallel projections

The visual rays are perpendicular to the projection plane, so the projection is said to be orthographic (orthogonal)

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Types of projections

ISOMETRIC

PROJECTIONS

CONICAL PROJECTIONS

OBLIQUE PROJECTIONS

MULTI-VIEW

PARALLEL PROJECTIONS

ORTHOGRAPHIC PROJECTIONS

Let’s look here next

Multi-view orthographic

projections

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Multi-view orthographic

projections TOP VIEW

FRONT VIEW RIGHT SIDE VIEW

Here is the usual representation of views in multi-view orthographic projections.

This type of drawing is used in technology because it allows description without deforming the faces of objects.

�Top view

�Front view, and

�Right Side view

are three commonly used views in multiview projection

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Multi-view

orthographic

projections

Multi-view orthographic projections are a part of parallel projections. In this type of drawing, the observer is considered to be at an infinite

distance. The projecting lines are parallel to one another.

These projections are also

orthographic since both the observer and the object are perpendicular to the projection plane.

Multi-view orthographic

projections Another distinguishing element in multi-view projections is that one of the faces of the object to be drawn is placed parallel to the projection plane.

That is why, in most cases, one must draw several views of the object to portray it completely.

The observer can only see one side at a time.

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Multi-view orthographic

projections In technical drawing, the views are flat figures (two dimensions) that we see from directly in front of each object.

Width

Height

Multi-view orthographic

projections In the type of projections used in North America, we imagine the object being drawn in the center of a transparent box.

The different views of the object are projected onto the sides of this box.

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Multi-view orthographic

projections One of these views is designated as the front view of the object. We usually choose the face that best portrays the object.

The choice of the front view determines the placement of the other views.

Multi-view orthographic

projections The projection box and its six views are spread in such a way as to place all the views on the same plane.

The other views pivot around the front view.

BOTTOM VIEW

LEFT SIDE VIEW REAR VIEW FRONT VIEW RIGHT SIDE VIEW

TOP VIEW

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Multi-view orthographic

projections Among the six possible views, we will choose to portray those necessary to the description of the shape of the object.

FRONT VIEW RIGHT SIDE VIEW

TOP VIEW

VUE DE GAUCHE VUE ARRIÈRE

BOTTOM VIEW

Three views are usually enough to portray an object. Many simple objects may only require one or two views.

Types of projections

AXONOMETRIC

PROJECTIONS

CONICAL PROJECTIONS

OBLIQUE PROJECTIONS

MULTI-VIEW

PARALLEL PROJECTIONS

ORTHOGRAPHIC PROJECTIONS

Let’s look here next

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ISOMETRIC Drawings

�In Isometric projection :

1) all three dimensions can be seen in one view

2) the intersecting edges of the object are on the axes that are spread at 120. This way the angles between all intersecting edges are either 120°°°°or 60°°°°.

Isometric projections

A cube shown with this type of projection pivots 45º to show three faces on the projection plane instead of a single face.

It is then tilted frontward or backward, allowing three faces to be observed.

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Types of projections

ISOMETRIC

PROJECTIONS

CONICAL PROJECTIONS

OBLIQUE PROJECTIONS

MULTI-VIEW

PARALLEL PROJECTIONS

ORTHOGRAPHIC PROJECTIONS Let’s look here next

Oblique parallel

projections �The observer is still at infinite distance, the projecting lines remain parallel to one another, but the object is placed so that the lines of vision are oblique (not perpendicular) to the projection plane.

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�OBLIQUE projections are unnatural

projections, because the angles

and lengths of edges are wrong. It

is impossible to actually see

objects in this way

�Any drawing that shows all three

dimensions (sides) of an object in

the same view, is called

A PERSPECTIVE DRAWING

List all projections that represent a

perspective drawing!

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(Gie

se

ck

e e

t a

l. Technical Drawing

, 1

2th

ed

itio

n.

20

00

)

Bibliography

GIESECKE, Frederick E., MITCHELL, Alva, SPENCER, Henry Cecil, HILL, Ivan Leroy, GYGDON, John Thomas et NGUYEN, Dinh N. « Dessin technique », Montréal, Éditions du Renouveau Pédagogique inc., 1982, 769 p.

JENSEN, C.H. « Dessin industriel », Montréal, McGraw-Hill, 1972, 752 p.

STIRLING, Norman. « Éléments de dessin industriel », Montréal, HRW, 1979, 372 p.

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Multi-view orthographic

projections TOP VIEW

FRONT VIEW RIGHT SIDE VIEW

Here is the usual representation of views in multi-view orthographic projections.

This type of drawing is used in technology because it allows description without deforming the faces of objects.

Activities with blocks

�A series of learning activities were created to give students (and teachers)

a better understanding of the four

views and placement of objects as well

as use of the lines.

�We need to review one more thing –

line convention before we do these!

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CONVENTIONAL LINES

CONVENTIONAL LINES

SUMMARY

Portrays surfaces and edges that are hidden from view

Indicates the placement of an imaginary cut.

Hidden feature line

A

B

C

D

E

F

G

H

NAME PURPOSE THICKNESS

J

LINE

Object line or visible outline

Cutting plane line

Break line

Leader

Portrays visible forms.

Indicate the surface imagined to have been cut.

Used to shorten the view of a part.

Indicates the part of a drawing to which a note refers

Is used to indicate the dimension. Dimension line Fine

Medium

Thick

Very thick

Center line Portrays the center of a round or circular object.

Fine

Fine

Fine

Fine

Is used to indicate the dimension. Extension line Fine

Section lines

100 %

50 %

25 %

AL7

Slide 38

AL7 Il y a confusion entre lignes "D" et "E" dans le texte francais. Dans le sommaire, "D" montre des lignes d'extension. A la diapo 12, "E" indique les lignes d'extension. A. Labelle, 09/10/2007

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CONVENTIONAL LINES

In a technical drawing, each type of line has its own significance. Each is distinguished from the other by a particular thickness or shape. The object above is drawn in isometric projection. It is portrayed on the left by three views. We will use this object to illustrate the principal lines found in technical drawing on the slides which follow.

8 -

LAMAGE

14 X 3 PROF.

45°

13

20

50

40

20

24

45

80

FACING

DEEP

AL4

CONVENTIONAL LINES

A

OBJECT LINE OR VISIBLE

OUTLINE

Slide 39

AL4 Représentée à droite ou plutôt à gauche???A. Labelle, 03/10/2007

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CONVENTIONAL LINES

The object line or visible

outline is made of a

continuous line that portrays

the visible forms of the object.

It is a thick line, its thickness

chosen to clearly show the

shape.

OBJECT LINE OR VISIBLE OUTLINE

AL5

CONVENTIONAL LINES

B B

HIDDEN FEATURE LINE

Slide 41

AL5 Dans la version française, voir les "é" qui ne sont pas de la même fonte.A. Labelle, 03/10/2007

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CONVENTIONAL LINES

B

The hidden feature line is

made of a dashed line that

portrays surfaces and edges

that are hidden from view.

The line is medium sized, half

the width of the one chosen for

the visible outline.

HIDDEN FEATURE LINE

CONVENTIONAL LINES

C

C

THE CENTER LINE

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CONVENTIONAL LINES

The center line is made from phantom lines. It is used to designate the axes of circular or cylindrical shaped objects. The line is half the width of the one used for hidden features. It is a fine line.

THE CENTER LINE

CONVENTIONAL LINES

D

DIMENSION LINE

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CONVENTIONAL LINES

DIMENSION LINE DIMENSION LINE

The dimension line is a fine line ending with an arrow. The purpose of these lines is to provide dimensions.

CONVENTIONAL LINES

45

80

40 20

40°

The dimension is a value used to indicate size in a technical drawing. This value is given in millimetres.

DIMENSION

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CONVENTIONAL LINES

E

45

80

50

13 40

24 20

40°

20

EXTENSION LINE

CONVENTIONAL LINES

45

80

50

13 40

24 20

40°

20

Extension lines are fine lines that indicate the placement of the dimensions.

EXTENSION LINE

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CONVENTIONAL LINES

F

Ø 8

FACING

Ø14 x 3 DEEP 13

40 24

20

40°

20

45

50

80

THE LEADER

CONVENTIONAL LINES

45

80

50

Ø 8

FACING

Ø14 x 3 DEEP 13

40 24

20

40°

20

The leader is used to indicate the part of the drawing to which a comment refers.

THE LEADER

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CONVENTIONAL LINES

G

13 40

24 20

40°

20

Ø 8

FACING

Ø14 x 3 DEEP

80

45

50

CUTTING PLANE LINE

CONVENTIONAL LINES

13 40

24 20

40°

Ø 8

FACING

Ø14 x 3 DEEP

The cutting plane line is very thick; this line is used to designate where an imaginary cut took place.

INFORMATION ON CUTS INFORMATION ON CUTS

80

45

50

CUTTING PLANE LINE

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The cutting plane line show where the object is cut. The arrows indicate the point of view of the observer.

The section view allows one to see inside the object. It makes the object simpler to understand by eliminating hidden feature lines.

We presume that the part between the cutting plane line and the observer has been removed.

The section is drawn in a view adjacent to the cutting plane line.

Section lines emphasise which part has been cut in the section view.

SUMMARY SUMMARY

TOP VIEW

CONVENTIONAL LINES

13 40

24 20

40°

20

H

Ø 8

FACING

Ø14 x 3 DEEP

50

45

80

SECTION LINES

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CONVENTIONAL LINES

45

13 40

24 20

40°

20

Ø 8

FACING

Ø14 x 3 DEEP

Section lines are fine lines used to indicate the surface imagined to have been cut.

50

80

SECTION LINES

CONVENTIONAL LINES

50

13 40

24 20

40°

20

H Ø 8

FACING

Ø14 x 3 DEEP

45

80

H

THE SHORT BREAK LINE

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CONVENTIONAL LINES

45

80

50

13 40

24 20

40°

20

Ø 8

FACING

Ø14 x 3 DEEP

The short break line is a thick, irregular line used to indicate a partial cut. This line is drawn freehand.

THE SHORT BREAK LINE

The long break line is a fine line used to shorten the view of a long part that can not be shown full length.

THE LONG BREAK LINE

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CONVENTIONAL LINES

SUMMARY

Portrays surfaces and edges that are hidden from view

Indicates the placement of an imaginary cut.

Hidden feature line

A

B

C

D

E

F

G

H

NAME PURPOSE THICKNESS

J

LINE

Object line or visible outline

Cutting plane line

Break line

Leader

Portrays visible forms.

Indicate the surface imagined to have been cut.

Used to shorten the view of a part.

Indicates the part of a drawing to which a note refers

Is used to indicate the dimension. Dimension line Fine

Medium

Thick

Very thick

Center line Portrays the center of a round or circular object.

Fine

Fine

Fine

Fine

Is used to indicate the dimension. Extension line Fine

Section lines

100 %

50 %

25 %

AL6

Slide 61

AL6 Il y a confusion entre lignes "D" et "E" dans le texte francais. Dans le sommaire, "D" montre des lignes d'extension. A la diapo 12, "E" indique les lignes d'extension. A. Labelle, 09/10/2007