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Auxiliary Views

Auxiliary Views. Engineering Graphics Stephen W. Crown Ph.D. Objective. To understand how to generate views that show inclined and oblique surfaces in true shape in multiview drawings

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Auxiliary Views

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  1. Auxiliary Views Engineering Graphics Stephen W. Crown Ph.D.

  2. 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

  3. 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

  4. 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 not 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

  5. Review: 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

  6. Example: Fold Line Method • Distances from the fold line in View A are equal to the distance from the fold line in View C • Follow projection lines to keep track of vertices • Use offset when creating View C from View A & B • Note that the projection lines are always perpendicular to fold lines.

  7. 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

  8. 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

  9. Projection Planes • A fold line represents the projection plane for the adjacent view • 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

  10. Lines • A line which is parallel to a fold line will appear true length in the adjacent view • A true length line which is perpendicular to a fold line will appear as a point in the adjacent view • Line 1-3 is parallel to the fold line in the right side view and true length line in the front view • Line 1-2 is true length in the right side view and is a point in the front view

  11. Lines • 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

  12. Surfaces • A Surface appears in “true shape” (undistorted) if it is parallel to the projection plane • A surface appears as an edge parallel to the fold line in all views adjacent to the true shape view of the surface • If any line on a surface appears as a point then the surface will appear as an edge • A surface which does not appear as an edge in any of the principle views is called an oblique surface

  13. Secondary Auxiliary Views • An oblique surface requires a secondary auxiliary view to show the surface in true shape

  14. 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 using fold lines and perpendicular projectors

  15. 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

  16. 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

  17. 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 • Perpendicular projectors are used to determine the location of vertices • Often only the inclined or oblique surface is shown in auxiliary views

  18. 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 measuring along projection lines in the top view • Vertices are numbered to help keep track of correct distances from reference planes

  19. Example: Secondary Auxiliary View • A true length line is identified in the right side view line 2-4 is parallel to the fold line in the front view, therefore 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

  20. 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) • The distance along projection lines are measured in relative views (OFFSET and DDOSNAP) • The secondary auxiliary view shows the oblique surface in true shape

  21. Memorize These Statements Before The Quiz • A fold line that is parallel to a line gives a view that shows the “true length” of the line • A fold line that is perpendicular to a “true length” line on a surface gives a view that shows the surface as an edge. • A fold line that is parallel to the edge view of a surface gives a view that shows the “true shape”

  22. 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

  23. 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

  24. 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

  25. Example: Secondary Auxiliary View • The true length line is used to get an edge view of the surface • A fold line perpendicular to the true length line gives a point view of the line in the adjacent view • Since the line is on the surface the surface will appear as an edge

  26. 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

  27. 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)

  28. Helpful Visualization Tools • Label surfaces • Label vertices - List nearest vertex first at each location (1,2) • Follow construction lines to determine location • Equal number of sides - A surface with 3 sides will have three sides in every view • Parallel edges - If lines are parallel in one view they will be parallel in every view

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