Orthographic Projection MultiView Drawing

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Orthographic Projection Multi-View Drawing
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Orthographic Projection

• a system of drawing views of an object using
  perpendicular projectors from the object to a
  plane of projection

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Revolving an Object to Produce the Six Basic Views
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Projection of an Object
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The Glass Box

• Imagine that the object you are going to draw is
  positioned inside a glass box, so that the large
  flat surfaces of the object are parallel to the
  walls of the box.
• From each point on the object, imagine a ray, or
  projector perpendicular to the wall of the box
  forming the view of the object on that wall or
  projection plane.

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The Glass Box
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Unfolding the Glass Box
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The Six Basic Views
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The Standard Arrangement of Views
TOP LEFT FRONT RIGHT BOTTOM REAR
Why must views be arranged so that they align? To
make it possible for someone to interpret the
drawing.
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Transferring Dimensions
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Using a Miter Line to Transfer Depth
1.
Draw miter line at 45 degrees at a convenient
distance to produce the desired view.
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Sketch light lines projecting depth locations for
points to miter line and then down into side view
as shown.
2.
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Project additional points, surface by surface.
3.
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4.
Draw the view locating each vertex of the surface
on the projection and miter line.
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Symbols for 1st 3rd Angle Projection
Third angle projection is used in the U.S., and
Canada
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Other Visualization Tools

• Number vertices in different views of multiview
  and isometric drawing
• Practice

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Multiview Sketching

• Represents a 3-D object with a series of 2-D
  views in contrast to pictorials which show all
  three dimensions in a single view
• Also called orthographic projection

Multiview Drawing
Pictorial
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Parallel projection

• Preserves true relationship between features
• Lines that are parallel on the object are
  parallel on the drawing

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Parallel versus Perspective Projection
Parallel
Parallel
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Projection Planes versus Views

• Projection planes
• Object formed from projection lines projected
  perpendicularly onto a projection plane
• Planes Horizontal, frontal, and profile
• Each projection plane is perpendicular to
  adjacent projection planes
• Principle views
• The object is rotated 90 degrees about the
  horizontal or vertical axis to give six principle
  views (top, bottom, front, rear, left, and right
  side)
• Common views top, front, and right side

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Only use Necessary Views

• One view drawings
• Sphere (Football)
• Two view drawings
• Cylindrical parts
• Show the circular and rectangular view
• Three view drawings
• Usually sufficient for all other drawings
• Top, front, and right side view

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Orientation and Placement of Views

• The most descriptive view should be selected as
  the front view
• The natural orientation of the part should be
  preserved if possible
• Views must be aligned
• Top view above front view
• Right view to the right of front view

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Hidden lines

• Represented with dashed lines
• Precedence of lines (visible, hidden, center)
• Views should be selected to minimize the use of
  hidden lines most descriptive view should be
  selected as the front view

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Fold Lines

• Represents a 90 degree fold between views
• Generally not shown on engineering drawings
  except when views other than the principle views
  (auxiliary views) are used.

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Terminology to Relate Views

• Adjacent view
• A view that is separated by a fold line
• The top view is an adjacent view to the front
  view
• Central View
• A view that is between two adjacent views
• The front view is the central view of the top,
  front, and right side view
• Related views
• Two views that are adjacent to a central view
• The top and right side view are related views
  since they are both adjacent to the front view

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Constructing a New View
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• The top and front views of a surface are shown
• The fold line represents a 90 degree fold between
  the views
• Parallel projection lines are perpendicular to
  the fold line

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3
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Constructing a New View

• A vertical fold line is drawn at an arbitrary
  distance from the front view
• Parallel projection lines are drawn from each
  vertex
• The common depth between the top and side view
  is used to locate each vertex on the projection
  lines

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Sketching Allows for the Quick Translation of
Thoughts to Paper

• Commit thoughts to paper before you lose an idea
• Avoid the of use mechanical tools (drawing tools
  are helpful for beginners)
• Does not need to be an exact representation
• objects may be simplified
• parts may be missing
• Avoid erasing
• as new ideas are developed make new sketches
• start with light lines and then darken with
  darker lead or heavier strokes

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Summary

• The six standard views are often thought of as
  produced from an unfolded glass box.
• Distances can be transferred or projected from
  one view to another.
• Only the views necessary to fully describe the
  object should be drawn.