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MECHANICAL DRAWING
Different views of an objectObjects may be drawn in different ways
PictorialMultiview
•Better for showing true size and shape
•Each view only shows two dimensions
•Better for visualizing the object
•All three dimensions shown on a single view
Multiview Drawing
Multiview Drawing
A multiview drawing is one that shows two or more two-dimensional views of a three-dimensional object.
Multiview drawings provide the shape description of an object. When combined with dimensions, multiview drawings serve as the main form of communication between designers and manufacturers.
Multiview Drawing
• Another name for orthographic projection is multiview drawing
• Involves visualization and implementation– Ability to see clearly in the mind’s eye an object– Process of drawing the object
Angles of Projection
• First-angle projection– Used by many European countries– Object is projected onto planes
from the first angle or quadrant• Front view projected to vertical plane• Top view projected to horizontal plane• Left-side view projected to profile
plane
TOP VIEW
FRONT VIEW RSIDE
Angles of Projection
• Third-angle projection– Standard for the United States– Third quadrant is used for
projection• Front view projected to vertical
plane• Top view projected to horizontal
plane• Right-side view projected to
profile plane
1.63 1.25
5.13
2.00
2.88
2.25
1.50
2.50
3.50
45°Ø1.52
TOP VIEW
FRONT VIEW R. SIDEVIEW
Choosing Views
• Most commonly used views– Front View– Top View– Right Side View
• Most descriptive view is typically designated as the Front View
Choosing Views
• Complex objects require three views to describe its shape
• Simple objects can be described with two views– Ex: Soda Can
• Thin objects can be described with only one view– Depth is given in a note– Ex: Erasing Shield
1.63 1.25
5.13
2.00
2.88
1.751.50
2.00
3.00
Ø2.22
TOP VI EW
FRONT VI EW R. SI DE VI EW
45°
SPECI AL CAM R. MI GLI ORATO 5/ 9/ 03 SCALE 1:1 16-52 12 NBHS
Placement of Views
• Views should be visually balanced within the working space
Steps for Centering a Drawing
.75
.25
8.50
7.00
10.5011.00
.50
.25 .25
• Draw border and title block using light construction lines• Draw diagonal lines from corners of border
Layout of Views
Steps for Centering a Drawing
• Add:– Length 5.13– Space 1.50– Width 2.00 – Horizontal 8.63
– Height 3.00– Space 1.50– Width 2.00– Vertical 6.50
1.63 1.25
5.13
2.00
2.88
1.751.50
2.00
3.00
Ø2.22
TOP VI EW
FRONT VI EWR. SI DEVI EW
45°
4.3"
3"
4.3"
3"
Steps for Centering a Drawing
• Draw a box the size of all views• Measure from the center:
– Half the width– Half the height
FRONT VI EWR. SI DEVI EW
TOP VI EW
5.13 1.50 2.00
3.00
1.50
2.00
Steps for Centering a Drawing
• Draw in views using light construction lines
Adding Details
• Add holes and features• Transfer horizontal and vertical features• Use miter line to transfer depth
TOP VI EW
FRONT VI EW R. SI DE VI EW
SPECI AL CAM R. MI GLI ORATO 5/ 9/ 03 SCALE 1:1 16-52 12 NBHS
Straight Edges
• Edges that are parallel to a plane of projection appear as lines
• Edges that are inclined to a plane of projection appear as foreshortened lines
POI NT
VI EW
TRUE LENGTH
TRUE LENGTH
FORESHORTENED
FORESHORTENED
Curved Edges
• Curved edges project as straight lines on the plane to which they are perpendicular
• Curved edges project as curved lines on the planes to which they are parallel or inclined
Normal Surfaces
Normal surfaces appear as an edge in two opposite principal views, and appear a surface in all other principal views.
Inclined Surfaces • Inclined surfaces appear as an edge in two
opposite principal views, and appear foreshortened (not true size) in all other principal views.
Oblique Surfaces
• Oblique surfaces do not appear either as an edge or true size in any principal view.
NO LI NE
NOLI NE
Intersections & Tangencies
• Where a curved surface is tangent to a plane surface, no line should be shown where they join
Intersections & Tangencies
• Where a plane surface intersects a curved surface, an edge is formed
LI NE
LI NE
What is Multiview drawing?
Ortho (straight) + graphic (drawing)
An orthographic view is drawn looking straight at one side of the object (at 90° to it)
Drawing more than one orthographic view of an object on the same page
Line of sight
Projection plane
Object
Orthographic projection is a technique that is used to create multiview drawings.
Orthographic projection is any projection of the features of an object onto an imaginary plane of projection. The projection of the features of the object is made by lines of sight that are perpendicular to the plane of projection.
Orthographic Projection
The best way to understand orthographic projection is to imagine an object contained inside a glass box.
Orthographic Projection
There is a total of six glass walls surrounding the object. Each wall represents a projection plane onto which a two- dimensional object view will be created.
Orthographic Projection
A projection plane, also referred to as a plane of projection or picture plane, is an imaginary surface that exists between the viewer and the object.
The projection plane is the surface onto which a two-dimensional view of a three-dimensional object is projected and created.
Projection Plane
Start by focusing only on the front projection plane.
A person standing in front of the object would see only the five corners identified in black.
1
2
3
4
5line of sight
at 90° a
ngle
to projection
plane
Orthographic Projection
Projection lines are used to project each corner outward until they reach the projection plane.
Orthographic Projection
A projection line is an imaginary line that is used to locate or project the corners, edges, and features of a three-dimensional object onto an imaginary two-dimensional surface.
Projection Lines
The visible edges of the object are then identified on the projection plane by connecting the projected corners with object lines.
Orthographic Projection
The orthographic projection process is then repeated on the other projection planes.
Orthographic Projection
A Question…Each of the blocks to the right have the same overall dimensions and colors.What else to they have in common?
Answer ….
They all have identical top
views!
HIDDEN LINES MUTLIVIEW DRAWINGS
We place hidden lines in a drawing to do the following things:
1. Show hidden features
2. Clarify the position and shape of features
3. Make the “plate” more readable
(NOTE: The term “plate” refers to a finished drawing.)
How many views?Cubes (like these dice) have 6 sides
Since each side of the die will have its own view…then there must be SIX possible orthographic views!
Front
How many views?Cubes (like these dice) have 6 sides
Since each side of the die will have its own view…then there must be SIX possible orthographic views!
Front
Top
How many views?Cubes (like these dice) have 6 sides
Since each side of the die will have its own view…then there must be SIX possible orthographic views!
Front
Top
Right Side
How many views?Cubes (like these dice) have 6 sides
Since each side of the die will have its own view…
The Front, Top, and Right Side are the views that are usually drawn.
then there must be SIX possible orthographic views!
Front
Top
Right Side
Back
Bottom
Left Side
Where do the views go?All the views MUST be arranged correctly
Imagine “unfolding” the cube to get proper view alignment.
The back view can be placed in any of these four locations.
How does this work on other objects?
Place the object in a glass box
Top view goes above
Then “unfold” the box
R.Side view goes to the right
Front view is always central
What about details you can’t see?
Hidden lines show details that are not seen in all views
Draw hidden lines (dashed) to show the detail
Project from hidden detail to the other views
ANIMATED EXAMPLES
http://dossin.weebly.com/3-multi--view-orthographic-projection-drawing.html
Multiview Drawing REVIEWAn orthographic view is drawn looking straight at one side of the object (at 90° to it)
There are 6 possible orthographic views: Front, Back, Top, Bottom,
Left Side, Right Side
The Front, Top, and R.Side views are usually all that are drawn
Hidden lines show details you can’t see in all views
Centering a Multiview Drawing Review
Make a sketch of the views needed for the drawing.The space between the views is 1 ½”What are the measurements needed to center the drawing?What is the overall size of the box for the views?
Centering a Multiview Drawing Review
1.75
1.5
1.56.50
3.50
3.50
11.50
6.75
Layout of the 6 ViewsSketch the layout of the 6 views of this object and label the views.
TOP
FRONTREAR L. SIDE
BOTTOM
R. SIDE