INTRODUCTION
TO
COMPUTER AIDED DESIGN
By
DINBANDHU
Assistant Professor
Vidya Vihar Institute of Technology, Purnea
Contents
CAD/CAM definition
The Product Cycle and CAD/CAM
Introduction to Computer Technology
Computer Programming Languages
Fundamentals of CAD
The Design Process
The Application of Computers for design
Benefits of CAD
CAD Hardware
CAD Software
CAD/CAM Defined
CAD/CAM means computer-aided design and computer-aided manufacturing. It is the
technology concerned with the use of digital computers to perform certain functions in
design and manufacturing.
CAD can be defined as the use of computer systems to create, modify, analyze, or
optimize an engineering design.
Computer
System
CAD CAD
Hardware Software
Fig. 1: Computer system configuration for CAD
CAD/CAM Defined
CAM can be defined as the use of computer systems to plan, manage, and control the
operations of a manufacturing plant through either direct or indirect computer interface
with the plant’s production resources.
The applications of CAM fall into two broad categories:
1. Computer monitoring and control
2. Manufacturing support applications
CAM
Computer Manufacturing
monitoring and support
control applications
Fig. 2: Applications of CAM
CAD/CAM Defined
1. Computer monitoring and control: These are direct applications in which the
computer is connected directly to the manufacturing process for the purpose of
monitoring or controlling the process. Computer monitoring and control can be
separated into monitoring applications and control applications.
a. Computer process monitoring: It involves a direct computer interface with the
manufacturing process to observe the process and associated equipment and collects
data from the process.
b. Computer process control: It goes one step further than monitoring by not only
observing the process but also controlling it based on the observations.
Computer Process
Process data
(a)
Process data
Computer Control Signals Process
(b)
Fig. 3: Computer monitoring and control: (a) Computer monitoring ; (b) Computer control
CAD/CAM Defined
2. Manufacturing support applications: These are indirect applications in which
the computer is used in support of the production operations in the plant, but there
is no direct interface between the computer and the manufacturing process. Here
computer serves a support role in the manufacturing operations and is used “off-
line” to provide plans, schedules, forecasts, instructions and information by which
the firm’s production resources can be managed more effectively.
Process data
Manufacturing
Computer
Control Signals operations
Fig. 4: Manufacturing support applications
The Product Cycle & CAD/CAM
Various activities + functions = Product Cycle
Product Design
Drafting
concept engineering
Order new
Customers Process
equipment
and markets planning
and tooling
Quality Production
Production
control scheduling
Fig. 5: Product Cycle
The Product Cycle & CAD/CAM
Computer-aided Computer-automated drafting
design and documentation
Product Design
Drafting
concept engineering
Order new Computer-aided
Customers and equipment Process
markets and tooling planning process planning
Quality Scheduling
Production
control
Computer-aided Computer controlled Computerized scheduling,
quality control robots, machines, etc. MRP, shop floor control
Fig. 6: Product Cycle revised with CAD/CAM overlaid
Computer Technology
The central and essential ingredient of CAD/CAM is the digital computer.
The modern digital computer is an electronic machine that can perform mathematical
and logical calculations and data processing functions in accordance with a
predetermined program of instructions.
There are three basic hardware components of a general-purpose digital computer:-
a. Central processing unit (CPU)
b. Memory
c. Input/output (I/O) Section
Peripheral devices
CPU (reader, printer, etc.)
Input/output or
Control mass memory
unit
Arithmetic
logic
unit Memory
Computer Outside world
Fig. 7: Basic hardware structure of a digital computer
Fundamentals of CAD
Modern CAD systems are based on Interactive Computer Graphics (ICG).
ICG is a system in which computer is used to create, transform, and display data in the
form of pictures or symbols.
The ICG system and the human designer are the major components of a CAD system.
Interactive computer graphics is a tool used by the designer to solve a design problem.
In effect, the ICG system magnifies the powers of the designer. This has been referred
to as the synergistic effect.
The designer performs the portion of the design process that is most suitable to human
intellectual skills (conceptualization, independent thinking) whereas the computer
performs the task best suited to its capabilities (speed of calculations, visual display,
storage of data), and the resulting system exceeds the sum of its components.
Fundamental reasons for implementing a CAD system
1. To increase the productivity of the designer.
2. To improve the quality of the design.
3. To improve communication.
4. To create a database for manufacturing.
The Design Process
It is an iterative procedure, given by Shigley, for designing something. It consists of six
identifiable phases.
Recognition of
need
Definition of
problem
Synthesis
Analysis and
optimization
Evaluation
Presentation
Fig. 7: The general design process
