TA 101: Technical Arts II Dr. Prishati Raychowdhury Department of Civil Engineering IIT Kanpur Office: FB 336; Phone:

Orthographic Projection Lecture 3

How would you explain simple shapes? One view is sufficient to explain because of the symmetry

How would you observe this object? At least two views are needed to describe this object

How about this object?

Projection 2D representation of 3D objects (e.g., real world 3D objects to a 2D drawing sheet) Straight lines are drawn from various points of an object to meet a plane, and the object is said to have projected on that plane Four methods of projections are commonly used: 1)Orthographic projection 2)Isometric projection 3)Oblique projection 4)Perspective projection

Orthographic projection o The rays are perpendicular to the plane of projection o The rays forming an image on the plane of projection are parallel to each other o The observer is at infinity

Three orthographic views Top View Front ViewSide View (Right)

Three Major Axes x y z Viewing parallel to Z axis Viewing parallel to X axis Viewing parallel to Y axis

Observe Parallel to Y Axis x z x y z

Observe Parallel to Z Axis x y z x y

Observe Parallel to X Axis x y z y z Are we missing anything?

y z x y z

Glass box concept for orthographic projection

Principal views Six principal views can be created by looking at the object from different directions However, for most objects, three orthographic views are generally adequate

During the unfolding process, the frontal plane remains stationary All other planes revolve outwardly from original position till they lie in the frontal plane Hinge lines of glass box are also known as folding lines Hinge lines

Imagine the object is placed inside a glass box

Front view Side/Profile view Top view

Front viewSide/Profile view Top view Hinge lines

Drawing orthographic views: 45 0 x y x z y z

Important Notes Always use a 45 o miter line for reflecting the profile views. Draw views concurrently, using projections. Use H pencil for object lines, hidden lines, dimensions, lettering etc. Use 2H pencil for all construction lines. A professional drawing does not contain quadrants or projection lines. However, in this course, you SHOULD NOT ERASE the construction lines after completing your drawing, unless specified otherwise.

Drawing orthographic views: Example

Thank you..