Engineering Graphics Essentials with AutoCAD 2016 Instruction by Kirstie Plantenberg
Book Details :
LanguageEnglish
Pages99
FormatPDF
Size7.0 MB


Engineering Graphics Essentials with AutoCAD 2016 Instruction by Kirstie Plantenberg



In Chapter 2 you will learn the importance of engineering graphics and how to create an orthographic projection. An orthographic projection describes the shape of an object. It is a two dimensional representation of a three dimensional object. Different line types are used to indicate visible, hidden and symmetry lines. By the end of this chapter, you will be able to create a technically correct orthographic projection using proper projection techniques.

In Chapter 2 you will learn the importance of engineering graphics and how to create an orthographic projection. An orthographic projection describes the shape of an object. It is a two dimensional representation of a three dimensional object. Different line types are used to indicate visible, hidden and symmetry lines. By the end of this chapter, you will be able to create a technically correct orthographic projection using proper projection techniques.

An orthographic projection enables us to represent a 3-D object in 2-D (see Figure 2.2-1). An orthographic projection is a system of drawings that represent different sides of an object. These drawings are formed by projecting the edges of the object perpendicular to the desired planes of projection. Orthographic projections allow us to represent the shape of an object using 2 or more views.

These views together with dimensions and notes are sufficient to manufacture the part.  When constructing an orthographic projection, we need to include enough views to completely describe the true shape of the part. The more complex a part, the more views are needed to describe it completely. Most objects require three views to completely describe them.

The standard views used in an orthographic projection are the front, top, and right side views. The other views (bottom, rear, left side) are omitted since they usually do not add any new information. It is not always necessary to use the three standard views. Some objects can be completely described in one or two views. For example, a sphere only requires one view, and a block only requires two views.  The front view shows the most features or characteristics of the object. It usually contains the least number of hidden lines.

The exception to this rule is when the object has a predefined or generally accepted front view. All other views are based on the orientation chosen for the front view. The top, front, and bottom views are all aligned vertically and share the same width dimension. The left side, front, right side, and rear views are all aligned horizontally and share the same height dimension (see the figure shown in Exercise 2.3-1).


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