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Orthographic Projection – Multi-View Drawing. Orthographic Projection. a system of drawing views of an object using perpendicular projectors from the object to a plane of projection. Revolving an Object to Produce the Six Basic Views. Projection of an Object. The Glass Box. - PowerPoint PPT Presentation
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Orthographic Projection – Multi-View Drawing
Orthographic Projection
a system of drawing views of an object using perpendicular projectors from the object to a plane of projection
Revolving an Object to Produce the Six Basic Views
Projection of an Object
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.
The Glass Box
Unfolding the Glass Box
The Six Basic Views
Why must views be arranged so that they align?To make it possible for someone to interpret the drawing.
TOPLEFT FRONT RIGHT
BOTTOM REAR
The Standard Arrangement of Views
Transferring Dimensions
Using a Miter Line to Transfer Depth1.
Draw miter line at 45 degreesat a convenient distance to produce the desired view.
2. Sketch light lines projecting depth locations for points to miter line and then down into side view as shown.
3. Project additional points, surface by surface.
4. Draw the view locating each vertex of the surface on the projection and miter line.
Symbols for 1st & 3rd Angle Projection
Third angle projection is usedin the U.S., and Canada
Other Visualization Tools
• Number vertices in different views of multiview and isometric drawing
• Practice
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 DrawingMultiview Drawing
PictorialPictorial
Parallel projection• Preserves true relationship
between features– Lines that are parallel on the object
are parallel on the drawing
Parallel versus Perspective Projection
ParallelParallelParallelParallel
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
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
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
Hidden linesHidden 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
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.
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
Constructing a New View
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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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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1111
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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
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.