Auxiliary Views

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Auxiliary Views

• Engineering Graphics
• Stephen W. Crown Ph.D.

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Objective

• To understand how to generate views that show
  inclined and oblique surfaces in true shape in
  multiview drawings
• To better understand the manipulation of 3-D
  objects using successive 90 degree rotations in
  preparation for solid modeling

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Outline

• Definition and Use
• Fold Line Method
• Primary Auxiliary Views
• Review of descriptive geometry
• Example Inclined surface
• Secondary Auxiliary Views
• Example Oblique surface
• Example A surface with no true length lines

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Auxiliary Vs. Principle Views

• Principle planes
• Horizontal (Top and bottom view)
• Frontal (Front and back view)
• Profile (Left and right side view)
• Auxiliary views
• Definition An orthographic view that is
  projected into a plane that is parallel to any of
  the principle planes
• Purpose To show the true shape of a detail that
  does not lie in on of the principle planes

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Fold Line Method

• A fold line (hinge) may be placed between
  adjacent views to aid in the construction and
  interpretation of multiview drawings
• Projection lines are always perpendicular to fold
  lines
• The distance from a fold line to any specific
  point on an object is the same for any related
  views (ex. top and side view)
• Fold lines represent a 90 degree rotation in
  viewpoint which has been rotated about the fold
  line

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Example Fold Line Method

• Distances from the fold line in the right side
  view are equal to the distance from the fold line
  in the top view
• Follow projection lines to keep track of vertices
• Use offset when drawing in AutoCAD
• Note that the inclined surface does not appear in
  true shape in any of the principle views

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Primary Auxiliary View

• Definition Any view that is projected from
  (adjacent to) one of the principle views and
  which is not parallel to any of the principle
  planes
• A primary auxiliary view is perpendicular to only
  one of the principle planes
• Any inclined surface may be shown in true shape
  in the appropriate primary auxiliary view
• If the fold line for an auxiliary view is
  parallel to the edge view of an inclined surface
  the inclined surface will appear in true shape in
  the auxiliary view

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Example Primary Auxiliary Views

• Use the UCS command to rotate about the Z axis
  and align the x axis up with the inclined surface
• Project perpendicular projection lines from the
  inclined surface (ORTHO)
• Determine the depth of each point from related
  views (OFFSET)
• Use DDOSNAP to quickly select features

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Review Descriptive Geometry

• Every point appears in every view
• The distance between points does not remain
  constant between views
• The apparent length of a line will never exceed
  its actual length
• A line appears true length if it lies in a plane
  parallel to the projection plane
• A line which is not parallel to the projection
  plane appears foreshortened
• A line which is perpendicular to the projection
  plane appears as a point

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Review Descriptive Geometry

• More About Lines
• A line which is parallel to a fold line will
  appear true length in the adjacent view defined
  by the fold line
• A true length line will appear as a point in an
  adjacent view defined by a fold line which is
  perpendicular to the true length line
• All views adjacent to a point view of a line will
  show the line in true length
• A line which does not appear true length in any
  of the principle views is called an oblique line

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Review Descriptive Geometry

• Planes
• A plane appears in true shape (undistorted
  angles and all lines true length) if it is
  parallel to the projection plane
• A plane appears as an edge (a single line) which
  is parallel to the fold line in all views
  adjacent to the true shape view of the plane
• If any line on a plane appears as a point then
  the plane will appear as an edge
• A plane which does not appear as an edge in any
  of the principle views is called an oblique plane

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Review Visualization Tools

• Using Labels on Pictorials and Multiview Drawings
• Label surfaces
• Label vertices
• list nearest vertex first at each location (3, 1)
• follow construction lines to determine location
• distance from fold line along projection lines is
  the same for related views
• Recognize Similar Shapes in Different Views
• Equal number of sides
• Parallel edges

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Secondary Auxiliary Views

• An oblique surface requires a secondary auxiliary
  view to show the surface in true shape

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Secondary Auxiliary Views

• Definition A secondary auxiliary view is any
  view which is not perpendicular to any of the
  principle views
• Purpose A secondary auxiliary view is used to
  show the true shape of an oblique surface
• A secondary auxiliary view is constructed as an
  auxiliary view to a primary auxiliary view
• May be constructed using fold lines, reference
  lines, and perpendicular projectors

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Example Secondary Auxiliary View

• The top view shows the oblique surface
• A secondary auxiliary view is needed to show the
  surface in true shape
• The lengths of sides and angles are distorted in
  all other views
• Perpendicular projection lines and reference
  planes are used to construct the right side view
  from the front and top view

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Example Secondary Auxiliary View

• A true length line on the oblique surface is
  identified in the right side view
• Placing a fold line which is perpendicular to the
  true length line gives the edge view of the
  surface
• This auxiliary view is a primary auxiliary view
• The edge view of the surface is needed to obtain
  the true shape view

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Example Secondary Auxiliary View

• A fold line which is draw parallel to the edge
  view of the oblique surface gives the secondary
  auxiliary view showing the surface in true shape
• Reference planes and perpendicular projectors are
  used to determine the location of vertices
• Often only the inclined or oblique surface is
  shown in auxiliary views

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Example Secondary Auxiliary View

• Simplify the construction of drawings by starting
  with only a portion of the drawing
• The right side view is constructed by using
  parallel projection lines and reference planes
• Vertices are numbered to help keep track of
  correct distances from reference planes

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Example Secondary Auxiliary View

• A true length line is identified in the right
  side view
• line 2-4 is parallel to the fold line between the
  front and right side view
• line 2-4 is a true length line in the right side
  view
• A fold line perpendicular to the true length line
  gives the edge view of the oblique surface

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Example Secondary Auxiliary View

• Use UCS to rotate about the Z axis and align the
  X axis with the edge view of the oblique surface
• Perpendicular projection lines are constructed
  (ORTHO)
• Reference planes are used to measure distances
  along projection lines (OFFSET and DDOSNAP)
• The secondary auxiliary view shows the oblique
  surface in true shape

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Another Example

• The top view and front view of a surface is shown
• Is an auxiliary view needed to show the surface
  in true shape?
• Yes The surface does not appear as an edge in
  either view

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Example

• Construct the right side view using projection
  lines and reference planes
• Note that there are no true length lines in any
  of the principle views

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Example Secondary Auxiliary View

• Since the surface does not appear as an edge in
  any of the principle views the surface is oblique
  and requires a secondary auxiliary view
• A line is drawn on the surface which is parallel
  to the fold line between the front and right side
  view
• This line appears as a true length line in the
  right side view

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Example Secondary Auxiliary View

• The true length line is used to get an edge view
  of the surface
• A fold line which is perpendicular to a true
  length line gives a point view of the line in the
  adjacent view
• A plane which contains a line that appears as a
  point will appear as an edge

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Example Secondary Auxiliary View

• The secondary auxiliary view gives the true shape
  of the surface
• The secondary auxiliary view is constructed by
  placing a fold line parallel to the edge view of
  the surface

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Example Secondary Auxiliary View

• Fold lines are labeled by the name of the
  principle plane or the level of auxiliary view
• Primary auxiliary view (1)
• Secondary auxiliary view (2)