orthographic projection + purpose
look straight at the object (front, top, side) with your line of sight at 90 degrees to the projection plane
ideal for manufacturing and measurement
why do we have a 90 degree projection plane for orthographic projections
ensure that lengths parallel to the projection plane are shown in true size, and angles lying that plane are preserved
(dimensions are not distorted by perspective)
glass box model
imagine placing a 3D object inside a transparent glass box. each face of the box serves as a plane of projection: front, top, bottom, left, right, and rear. Rays of sight are projected perpendicularly from the object until they strike the box walls, the resulting outlines on each wall are the orthographic views
ISO
first angle standards for projection
ANSI
third angle standards for projection
first angle projection + who uses it
object is placed between the observer and the plane of projection.
Europe
third angle projection + who uses it
plane of projection is placed between the observer and the objects
Canada and USA
do we use ANSI or ISO
ANSI (third angle projection)
principal views of orthogonal projection
front, top, right-side
how do we choose the front view
shows the object’s most characteristic shape and typically contain the greatest number of visible features
in an orthogonal view, feature’s dimensions need to ______
line up
why do we need section views
hidden lines can be cluttered and hard to interpret for internal/hidden components.
they reveal interior features more clearly and reduce the overuse of hidden lines
full section
cutting plane goes completely through the object
half section
cutting plane goes halfway through the object
offset section
cutting plane follows a stepped path
broken out section
cutting plane removes only a small portion
when you make a section, what must happen (hint section lining or hatching)
section lining or hatching, where the material was actually cut in half. Ie. if ON that cutting plane, the material would have gone through it, you need hatching. If there is a gap between the object and the cutting plane, you don’t need hatching
Full section by hand procedure
- decide where to locate the cutting plane so that it passes through the most important internal features
- draw a cutting plane line on the parent view; this line is drawn as a phantom line
- project the intersection of the cutting plane with the object onto the section view\
- BY THE CONVENTION ADD CROSSHATCHING
- remove unecessary hidden lines in the section view
what do arrows indicate on a section line
indicate the direction in which the section is viewed
how do you represent change of plane behind the cutting plane
a solid line
what does hatching mean on section view
the cutting plane actually cut through material
what are half sections useful for + examples (4)
parts that are symmetric about an axis, such as flanges, pulleys, bearings and many rotating machine elements
in a half section how much of the object do you remove + what does this look like on the orthogonal drawing
one quarter. depicts internal details on one side and external details on the other in a single view
what do you hatch on the half section view.
only the sectioned half
