SEGMENT 5: Orthographic Projection
Orthographic Projection Vocabulary
Multiview Drawing- The views are arranged in a standard order so that anyone trained in drafting can understand them. This type of graphic representation is called multiview drawing.
Normal Views- The front, top, and right-side views are known as the normal views because they are the ones most often used to describe objects in technical drawing.
Orthographic Projection- The views that make up multiview drawings are developed using the principles of orthographic projection. This is the process of projecting two or more views of an object onto imaginary planes perpendicular to the object.
First-Angle Projection- In European countries, the accepted method of projecting views onto the quadrants, or angles, is known as first-angle projection. Using this method, the object is projected from the first angle, or quadrant, onto the other quadrants.
Third-Angle Projection- Third-angle projection uses the same basic principles as first-angle projection. But the object is projected onto the planes from the third angle, not the first angle. This method is used in the United States and Canada.
Normal Views- The front, top, and right-side views are known as the normal views because they are the ones most often used to describe objects in technical drawing.
Orthographic Projection- The views that make up multiview drawings are developed using the principles of orthographic projection. This is the process of projecting two or more views of an object onto imaginary planes perpendicular to the object.
First-Angle Projection- In European countries, the accepted method of projecting views onto the quadrants, or angles, is known as first-angle projection. Using this method, the object is projected from the first angle, or quadrant, onto the other quadrants.
Third-Angle Projection- Third-angle projection uses the same basic principles as first-angle projection. But the object is projected onto the planes from the third angle, not the first angle. This method is used in the United States and Canada.
Orthographic Projection Part 1The views that make up multiview
drawings are developed using the principles of orthographic projection. In first-angle projection, the object is pro- jected onto the planes from the first angle, or quadrant. Third-angle projection uses the third quadrant, not the first, for projection. The number of views needed to describe an object completely depends on its shape and characteristics. Multiview drawing represents an object on paper using views as seen from different positions. These views are then arranged in a standard order so that trained drafters can understand them. Views are chosen based on an object’s characteristic view, its normal position, and the relative number of hidden lines in the views that are being considered. |
Orthographic Projection Part 2Although CAD techniques may differ
in their approach from board drafting techniques, all drafting principles apply equally to both. However, CAD has tools that add efficiency to the processes. One way to create a multiview drawing using CAD is to create the necessary views independently of each other. A second method for creating multiview drawings is to extract the necessary views from a 3D model. |