How We Represent Objects Through Drawing - Physics …physicsteacher.ca/Science and Technology...
Transcript of How We Represent Objects Through Drawing - Physics …physicsteacher.ca/Science and Technology...
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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
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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