Mulitview Drawing Notes

Multiview Drawings
In engineering, various methods are used to represent objects. Among these, the
engineering drawing or multiview drawing is a major means of communicating the
design concept. In this method, orthogonal projection is used to draw and define
an object.
Orthographic Projection
Pictorial drawings provide a three dimensional view of an object as it would appear
to the observer. Generally, multiview and pictorial drawings are used together to
provide a complete picture of the object being represented.
Pictorial Drawing
Projecting Views
Orthographic projection is the system of representing objects by using more than
one view to define the object. There are actually 4 methods of orthographic
representation. In this course you will be studying and using the Third-Angle
Projection method of representation. Third-Angle Projection is the most widely
used method today.
The Third-Angle projection method is an orthographic representation in which the
object to be represented and seen by the viewer appears behind the coordinate
viewing planes on which the object is orthographically projected.
An easier way to think of this method of projection is to imagine viewing the
object and its various views through a glass box. In fact, third-angle projection is
sometimes referred to as the glass-box method.
Each face of the box represents one of
the six different planes of projection
Third Angle (glass-box) Viewing Planes
Using this method, each view is projected onto its respective viewing plane. Each
viewing plane is referred to as a plane of projection. The six principal planes of
projection are: front, top, bottom, left side, right side, and back. In determining
how the particular view will look (on the plane of projection), imagine yourself
looking at the object through each side of the glass box.
Object with Viewing Directions Indicated
View in Direction
View From
Generally not all of these projections are used in drawings. In determining the
number of projections to use, the rule of thumb is include only as many views
that are needed to represent the object accurately.
When laying out your various views on your drawing, start with the Principal View.
The principal view is the view that shows the most about the product. It is usually
the longest view and shows the major shape or profile. Sometimes it may be
difficult to determine which view should be used as the principal view. In
situations such as this, use your own discretion. This principal view is then
designated as the Front View.
After your front view is selected, imagine folding out each flap of the box
towards the front view.
All 6 Orthographic Views Positioned Correctly on Drawing Surface
Hidden Surfaces & Edges
Many objects drawn in engineering contain many features (lines, holes, etc.) that
cannot be seen when the object is viewed from a particular angle. These hidden
details are normally required on the drawing to show the true shape of the object.
Hidden lines are used to illustrate hidden detail.
Hidden lines consist of short, evenly spaced dashes. In CAD, hidden lines are given
a different color and are generally assigned to a separate layer.
Sample Projections
Examples of orthographic projection
Examples of objects having hidden features
Examples of objects having sloping surfaces
Examples of objects having circular features
View Spacing &Alignment
For clarity and good appearance, the views should be well balanced on the
drawing surface. In determining the alignment and spacing between views, the
drafter must consider the size of the object to be drawn, the number of views,
the scale of the printed drawing, and the space between views.
When determining the space between drawings, the drafter also needs to allow for
the placement of dimensions (to be covered in a later unit).
When laying out your views, view alignment is a must. Actually, view alignment is
a natural by-product of proper drafting technique (to be demonstrated in the first
guided activity in this unit).
Notice that each view is perfectly aligned with the principal view (Front View).
Spacing, though important, need not be precise but should look balanced.
Indicated below is one technique you may find helpful in spacing your views.
First, determine the distance between borders.
Next, determine the total vertical and horizontal distances of the aligned
Subtract the horizontal total from the horizontal distance between borders
and subtract the vertical total from the vertical distance between borders.
Then divide these totals by the number of spaces required.
e.g. Consider the following drawing.
Horizontal distance between borders = 10 inches
Vertical distance between borders = 7.5 inches
Total of horizontal distances of views = 3.5 + 2.0 = 5.5 inches
Total of vertical distances of views = 1.5 + 2.0 = 3.5 inches
Horizontal empty space = 10 - 5.5 = 4.5 inches
Vertical empty space = 7.5 - 3.5 = 4.0 inches
Horizontal distance between views = 4.5 / 3 (# of spaces) = 1.5 inches
Vertical distance between views = 4.0 / 3 (# of spaces) = 1.33 inches
Title Block Placement
When creating engineering drawings, the drafter needs to consider title block
placement as well. Title blocks are acceptable in any corner of the drawing. When
considering their placement, take into account corners of the drawing that are not
heavily utilized (to avoid over crowding).