Transcript Engineering Graphics

Orthographic Multiview
Projection
Multiview Projection
Multiview Projection
The method of viewing an object to obtain a multiview projection is illustrated in figure a. Between
the observer and the object a transparent plane is located parallel to the front view. The view is
obtained by drawing perpendicular lines (projectors) from all points of the edges of the object to the
plane of projection (figure b). The piercing points of these projectors form lines on the projection
plane (figure c)
Multiview Projection
A similar procedure can
be used to obtain the top
view (figure a) and the
right-side view (figure b).
Multiview Projection
If planes of projection are placed parallel to the principal faces of the object, they form a “glass
box” as shown in figure a. Since the glass box has six sides, six views of the object can be
obtained.
To show the views on a flat sheet of paper it is necessary to unfold the planes so that they will all
lie in the same plane. All planes except the rear plane are hinged to the frontal plane (figure b).
Multiview Projection
The positions of the six planes after they have been
revolved are shown.
Multiview Projection
The front, top, and right-side views of the object are shown with folding lines between the views.
These folding lines correspond to the hinge lines of the glass box (figure a).
The H/F folding line is between the top and front views.
The F/P folding line is between the front and right-side views.
Folding lines are useful in solving graphical problems in descriptive geometry. As a rule folding
lines are omitted in industrial practice (figure b).
Multiview Projection
Since all depth dimensions in the top and side views must correspond accurate methods of
transferring these distances must be used.
The depth dimension between the top and side views can be transferred either with dividers or a
scale.
A 45 degree miter line can also be used to project the depth dimension between the top and side
views.
Views of an Object
The front view of an object should show the
object in its operating position. The front
view should also show the best shape of the
object and the most detail.
In the example the side of the automobile
was selected as the front view of the
drawing rather than the actual front of the
automobile.
Machine parts are often drawn in the
position that it occupies in the assembly
drawing.
Views of an Object
A production drawing should show only those views needed for a clear and complete shape
description of the object. Often only two views are needed to clearly describe the shape of an
object.
In selecting the views, show only those that best show the essential contours or shapes and
have the lease number of hidden lines.
Unnecessary or duplicate views are eliminated or not shown. In the example, the left side, rear,
and bottom views are eliminated.
Views of an Object
Often only two views are needed to clearly describe the shape of an object. In figure (a) the
right side view shows no significant contours of the object and is eliminated. In figure (b) the top
and front views identical so the top view is eliminated. In figure (c) all necessary information is
given in the front and top views so the side view is unnecessary.
Multiview Projection
If three views of an object are drawn using the conventional arrangement of views a large wasted
space is left on the paper (figure a). In such cases the profile plane may be considered hinged to
the horizontal plane instead of the frontal plane which results in better spacing of the views
(figure b).
Multiview Projection
No line should be drawn where a curved surface is tangent to a plane surface. When a curved
surface intersects a plane surface a definite edge is formed. Show are examples of
intersections and tangencies.
Multiview Projection
The correct method of representing fillets in connection with plane surfaces tangent to
cylinders is shown in figure a and figure b. These small curves are called runouts. Runouts
have a radius equal to that of the fillet and a curvature of one eighth of a circle (figure c).
Multiview Projection
Examples of
typical filleted
intersections.