ORTHOGRAPHIC PROJECTIONS
An orthographic projection is a technique used in technical drawing and engineering to represent a three-dimensional object in two dimensions. It provides a series of flat, two-dimensional views of an object from different perspectives. These views, called orthographic views, show the object as if it has been projected onto an imaginary box with planes that are perpendicular to each other.
In an orthographic projection, the object is typically shown in three main views: front view, top view, and side view. The front view represents the object as it would appear when looking directly at its front face. The top view shows the object as if looking down from above, and the side view displays the object from the side.
Each view provides specific information about the object's dimensions, shape, and features. By combining these different views, viewers can understand the object's complete geometry and how its various parts relate to each other in a detailed and precise manner.
Orthographic projections follow specific conventions and use standard symbols and lines to represent various features such as edges, surfaces, and hidden lines. These projections are widely used in fields like engineering, architecture, manufacturing, and design, where accurate and clear representation of objects is crucial for communication and construction purposes.
Background Knowledge:
Multiview Drawings
Another name for an orthographic projection is a multiview drawing. The standard three views of a multiview drawing are front, right side, and top view. These are the views drawn in an orthographic projection because a person looking at the drawing can see all the important aspects of that drawing needing only these views. The best way to think about how to get these views from a 3D object is to imagine the object in a glass box.
Glass Box Theory
Imagine that the object is inside a glass box and we are drawing the surfaces projected onto the glass box. If you were to open the box and unfold it, what you would see projected is the 2D views.
Once the box is unfolded you will have multiple 2D representations of your 3D object. These views are labeled based on the orientation you are looking at the object. Generally speaking the front view is the view that contains the most information on the object and from there you can assign the other views. The right and left side views are to the right and left of the front view. The top and bottom are you guessed it, the top and bottom based off of the front view and the back view is the view behind the front view.
In general though the only three views that are used is the front, top and right side because the other views only repeat the information given in those three. There are times when only two views are required because you can convey all the information with only those two views but in general we will be working with the standard three view drawing when talking about orthographic projections.
Practice Problems - Orthographic Projections
Look at each object's 3D isometric view and try to find which orthographic projection represents the object. There is only one correct answer for each object. Pay careful attention to what would be a hidden line based on the orientation you are looking at the object.
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PRODUCE AN ORTHOGRAPHIC DRAWING IN CAD
AUTOCAD
Example video on how to produce a simple orthographic projection in AutoCAD using a part drawing. The video explains how to project views from a starting front view drawing and how to keep everything aligned. It also shows how to use layers to produce the required line types in the drawing.
ONSHAPE
Step-by-step video on how to create a professional drawing sheet with orthographic views from your 3D model. We'll cover the basics, including setting up your sheet, adding views, dimensions, and annotations. Perfect for those new to Onshape or CAD drafting, this video will give you the skills to turn your 3D designs into clear, precise technical drawings.
In case you were wondering, the answers to the practice problems are : BEH, FJK, ILD, CGA