Orthographic Projection (1)

Orthographic ProjectionCreated by Steven Colgan

What is Orthographic Projection?•Orthographic Projection is a method of

representing a three dimensional object on paper using several two dimensional views.

•It is the international language of Engineers and Designers

How does it work?

•We look directly at the different faces of the object (90˚ to the face) and draw the lines that we see.

•Click here to view the movie

How many views?

•One view is never enough to describe an object.

•We need at least two views to accurately describe even the most simple of objects.

•Generally we se three views and arrange them as shown in the movie

•Click here to view the movie.•You can use as many views as the object

requires.

Is it really an international language?•Yes. However America and Australia

arrange the views differently.•This arrangement of views is called third

angle projection.•Click here to view the movie

How do I know which method is being used?•Each method has its own symbol and they

are as follows•First angle projection

•Third angle projection

How do I draw this symbol?

•The recommended proportions for the symbol are as follows

How did they get their names?

•The name first angle is derived from the objects position in the first quadrant of the planes of reference.

•The name third angle is derived from the objects position in the third quadrant of the planes of reference.

Is that it?

•Sometimes features of an object are hidden (for example they are at the back of the object)

•To show these features we add dashed lines in their place.

•Click here to view the movie•If a dashed line meets a thick line leave a

gap as shown•Click here to view the movie

There’s too many dashed lines!

• If there is too much hidden detail and the drawing becomes confusing use a sectional view

•Click here to view the movie•Draw the Hatching lines at 45˚ as shown•Always place the section line (the dashed

line that ends in arrows) exactly were you are cutting the object.

•To see more types of Sectional views click here

Anything else?

•Make sure you keep your drawing neat. •Recommended proportions are shown

below.•Keep construction lines light and finished

lines heavy