Computer-aided design (CAD) is a computerized system to assist design-
ers in design, development, and revision work. Designers are needed to
design new products and modify existing products as per requirements.
They often need to make optimized designs to cut down on product
costs. In addition, reduction of design time is also a vital requirement to
meet the project schedule. CAD provides excellent facilities to designers
to fulll their objective. Its many facilities include excellent visualization
of the designed product for better understanding, analysis at different
load conditions, and faster drawing generation. Due to its various facili-
ties, CAD became an essential tool to designers for creation of optimized
design within the scheduled time. CAD is utilized for component as well
as system designs. Process and piping designers are also using CAD from
the beginning of projects to the end. CAD facilitates working on different
engineering disciplines in the same project and ensures integration of all
the data for sharing, verication, and drawing generation. CAD adds some
advantages, including automation for reduction of repeated work, mecha-
nism analysis and tracing of curves, and animation for presentation.
Its capabilities are making CAD an unconditional signicant requirement
to designers.
1.1 CAD System Tools
It is obvious that not all product designs demand the same assistance from
CAD. In other words, different product designers demand different sets of
tools of CAD for assisting in the creation or modication of their design. A
simple product with fewer components or a single component may need
only faster 2-D drawing and design tools, whereas a robust design with a
large number of components demands a 3-D drawing with advanced sim-
plied presentation tools. Various CAD software is also available with dif-
ferent features and tools to suit the designer’s needs of different design
requirements. Software focusing on creation of mainly 2-D drawing with-
out the help of 3-D provides plenty of 2-D editing tools. A designer concep-
tualizes the product and plots orthogonal or isometric views in a 2-D plane.
Detail dimensioning and annotations are placed after nalizing the design,
2 Computer-Aided Design
and the nal drawing is prepared. In the case of comparatively larger or
robust designs, several designers or engineers from different disciplines
may be required to work on the same product or project. Partially com-
pleted 3-D designed models from different designers are integrated into a
system and veried or analyzed for collision/ease of access. Designers also
need other CAD facilities like analysis and mechanism at various levels of
design, that is, analysis of each component to optimize the cost or analysis
of large assembled structures exposed to different load conditions. In such
cases, requirement of tools also varies at different levels of design or design-
ers. Normally, high-end CAD software provides most of the tools required
for every level of design. Obviously, all the available tools are not required
for a single designer or design of a single product or system, and it is also an
inconvenience to designers if all the tools are provided on a single screen.
Therefore, sets of tools are categorized into modules for specic applica-
tions or to suit a designer’s specic needs. This way, CAD software provides
a choice of selection of modules to customers to suit their specic require-
ments, thus reducing the cost. Companies making small products use 3-D
and 2-D packages with standard available tools, whereas large companies
having products in different disciplines use various modules according to
their application. Normally, standard packages of 3-D CAD software con-
tain operational design tools for solid modeling. Sheet metal industries use
a sheet metal module as an add on. Similarly, surfacing, mechanism, and
analysis are also available as add-on modules. The right selection of CAD
software for the required work is also very signicant.
1.2 CAD Libraries
If the usability of an existing drawing or design increases, a great amount
of time and effort is obviously saved. It is always suggested to keep usable
drawings or designs in an organized manner to form a library and reuse the
items whenever applicable. Modern software is now provided with many
libraries like a material library and symbol library. Classication and nam-
ing of libraries may also be different in different software. General classica-
tions of libraries in commonly used 3-D software are described in this book.
The following libraries are important for the subjects point of view:
1. Material library
2. 2-D symbol libraries
3. 3-D component libraries
4. Customized library

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