Orthographic 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.