Orthographic Projections

Orthographic Projections are a collection of 2-D drawings that work together to give an accurate overall representation of an object. Orthographic Projections are a collection of 2-D drawings that work together to give an accurate overall representation of an object.

Defining the Six Principal Views or Orthographic Views

Which Views to Present? General Guidelines: Pick a Front View that is most descriptive of object Pick a Front View that is most descriptive of object Normally the longest dimension is chosen as the width (or depth) Normally the longest dimension is chosen as the width (or depth) Most common combination of views is to use: Most common combination of views is to use: Front, Top, and Side View Front, Top, and Side View Any other view different from the Principal Views is called an Auxiliary View Any other view different from the Principal Views is called an Auxiliary View

Third-angle Projection First-angle Projection First and Third Angle Projections First Angle – International First Angle – International Third Angle – U.S. Third Angle – U.S.

Conventional Orthographic Views Height Depth Width Front View Top View Right Side View

Is The Orthographic View OK?

Orthographic Must Be In Projection

Hidden and Center Lines Hidden Line – used to represent features that cannot be seen in the current view Centerlines – used to represent symmetry and to mark the center of circles and the axes of cylinders, and the axes of symmetrical parts, such as cylinders and bolts

For Example: 1. Visible 2. Hidden 3. Center

Two-View Drawings Some objects can be fully described by two views, look for: Some objects can be fully described by two views, look for: Symmetry or Bodies of Rotation Symmetry or Bodies of Rotation Front ViewRight Side View Front View Right Side

Other Two-View Examples

Hints for Orthographic Projection Sketching Identify the major features and overall dimensions of the object Identify the major features and overall dimensions of the object Do not use any straight-edge devices as a pencil guide when sketching by hand Do not use any straight-edge devices as a pencil guide when sketching by hand Start by drawing bounding boxes with light construction lines. Start by drawing bounding boxes with light construction lines. Keep views aligned while sketching Keep views aligned while sketching

Hints for Orthographic Projection Sketching Title Information is required – follow conventions Title Information is required – follow conventions Usage of construction lines is encouraged. Usage of construction lines is encouraged. Mandatory for circle or ellipse Mandatory for circle or ellipse Orthographic projection: Orthographic projection: Alignment of the views is important! Alignment of the views is important! Will not be graded, if not aligned Will not be graded, if not aligned

Hints for Orthographic Projection Sketching Map inclined and oblique faces to all three views Map inclined and oblique faces to all three views Follow the precedence of lines Follow the precedence of lines Darken all visible, hidden, and center lines Darken all visible, hidden, and center lines

Multi view (multi planar) projection Multi view is a method by which the exact shape of an object can be represented by two or more separate views produced on projection planes that are at right angles to each other.

Method of obtaining the views The views of the object may be obtained by either of the two methods: 1. Natural method 2. Glass box method

Natural method

Glass Box Approach Most powerful technique to understand orthographic projections Most powerful technique to understand orthographic projections Suspend the object with transparent strings inside a glass box Suspend the object with transparent strings inside a glass box Freeze the view from each direction (each of the six sides of the box) and unfold the box Freeze the view from each direction (each of the six sides of the box) and unfold the box Animation illustrates glass-box approach Animation illustrates glass-box approach

Glass Box Approach

Principles of Multi view Drawing 1. The front and top views are always in line vertically. 2. The front and side views are inline horizontally. 3. The front of the object in top view faces the front view 4. The front of the object in side view faces the front view

5. The depth of the top view is the same as the depth of the side view (or views). 6. The width of the top view is the same as the width of the front view. 7. The height of the side view is the same as the height of the front view. 8. A view taken from the above is a top view and must be placed above the front view. Principles of Multi view Drawing

9. A view taken from right,, in relation to the selected front, is a right side view and must be placed to the right of the front view. 10. A view taken from the left is a left side view and must be placed to the left of the front view. 11. A view from below is a bottom view and must be placed below the front view. Principles of Multi view Drawing