CAD, CAM it contains all introductory bits of introduction

1.  Unit 1: Computer Aided Design (CAD)
Unit Contents: Hardware required for CAD: Interactive input output devices,
Graphics software: general requirements and ground rules, 2-D curves like Line,
Circle, etc. and their algorithms, 2-D and 3-D transformations such as Translation,
Scaling, Rotation and Mirror.

2. Computer aided design:
 Computer-aided design (CAD) is the use of
computer systems to assist in the creation,
modification, analysis, or optimization of a
design.
 The computer system consist of a hardware &
software to perform the specialized design
function.
 Computer-aided design (CAD) hardware
includes the computer , one or more graphics
display terminals, keyboard, mouse and
equipment's.

3. Computer aided design:
 Computer-aided design (CAD) software includes computer programs to
implement computer graphics on the system plus application programs .
 Examples of application programs:-
 stress strain analysis of component,
 heat transfer calculation
 Mass property calculations
 Finite-element modeling
 Numerical control part programming

5. Computer aided manufacturing:
 Computer-aided manufacturing(CAM) is
defined as the use of computer system to plan,
manage & control the operation of
manufacturing plant through either direct or
indirect computer interface with plant.

6. Difference

7. Computer aided manufacturing:
 The application of CAM fall into two broad categories
1. Computer monitoring and control:- these are the direct application in
which computer is connected directly to the manufacturing process for
the purpose of monitoring or controlling the process.

8. Computer aided manufacturing:
 The application of CAM fall into two broad categories
2. Manufacturing support application:- These are the indirect application
in which the computer is used in support of the production operation in the
plant.

9. Terminology
 CAD— Computer Aided Design The use of computer methods to develop
the geometric model of the product in three-dimensional form, such that
the geometric and manufacturing requirements can be examined.
 CADD— Computer Aided Design and Drafting Combining the CAD
function with drafting to generate the production drawings of the part for
the purpose of downstream processing.
 CAE— Computer Aided Engineering The use of computer methods to
support basic error checking, analysis, optimisation, manufacturability,
etc., of a product design.
 CAM— Computer Aided Manufacturing Generally refers to the computer
software used to develop the Computer Numerical Control part programs
for machining and other processing applications.

10. Terminology
 CAPP— Computer Aided Process Planning The use of computers to
generate the process plans for the complete manufacture of products and
parts. Such as material requirement planning, computer aided scheduling,
etc.
 CATD— Computer Aided Tool Design Computer assistance to be used
for developing the tools for manufacture such as jigs and fixtures, dies,
and moulds.
 CAQC— Computer Aided Quality Assurance The use of computers and
computer-controlled equipment for assessing the inspection methods and
developing the quality control and assurance functions.

11. THE PRODUCT
CYCLE

12. THE PRODUCT CYCLE

13. THE PRODUCT CYCLE AND CAD/CAM

14. HARDWARE REQUIRED FOR CAD
 Typically, a stand-alone CAD system would include the following
hardware components
i. One or more design workstations. These would consist of: A graphics
terminal
ii. Operator Input devices
iii. One or more Plotters and other Output devices
iv. Central processing unit (CPU)
v. Secondary storage

16. The Design Workstation
 The workstation must accomplish five functions:
i. It must interface with the central processing unit.
ii. It must generate a steady graphic image for the user.
iii. It must provide digital descriptions of the graphic image.
iv. It must translate computer commands into operating functions.
v. It must facilitate communication between the user and the system.

17. The Graphics Terminal
 Image generation in computer graphics: Cathode ray tube (CRT)

18. Random Scan
 It uses an electron beam which operates like
a pencil to create a line image on the CRT
screen. The picture is constructed out of a
sequence of straight line segments. Each
line segment is drawn on the screen by
directing the beam to move from one point
on the screen to the next, where its x & y
coordinates define each point. After drawing
the picture, the system cycles back to the
first line and design all the lines of the
image 30 to 60 times each second. Random
scan is also known as a vector display or
stroke writing or calligraphic display.

19. Raster Scan
 In the raster scan approach, the viewing screen
is divided into a large number of discrete
phosphor picture elements, called pixels. The
matrix of pixels constitutes the raster. The
number of separate pixels in the raster display
might typically range from 256 × 256 (a total of
over 65000) to l024 × l024 (a total of over l,
000,000 points). Each pixel on the screen can be
made to glow with a different brightness.
Colour screens provide for the pixels to have
different colours as well as brightness. During
operation, the electron beam is swept across the
screen, one row at a time from top to bottom.

20. Raster Scan
 As the electron beam moves across each row,
the beam intensity is turned on & off to create
the pattern of illuminated spots. Picture
definition is stored in memory area called the
refresh buffer or frame buffer. This memory
holds the set of intensity value for all the screen
points. Store intensity values are then retrieved
from the refresh buffer & ‘painted’ on the
screen one row (scan line) at a time line. Each
screen point is refreshed as a pixel (picture
electron). At end of each line, the electron beam
returned to the line left side of the screen to
begin displaying the next scan line.

21. Input Devices
 The input devices are one of the major components of the CAD system. It
consists of a mechanism for the communication between the operator & the
system. The input devices convert the information into electronic signal &
send it to the computer system. The can be in the form of text, graphics or
sound.

22. Keyboard
 A alphanumeric keyboard is device which is used to communicate with the CPU to carry out
following function.
 - to start the program.
 - to initiate certain commands.
 - to communicate data in the form of words & numbers.
 Keyboard is similar to standard keyboard on typewriter, with some additional key.
 Functional keys(upper side), Alpha numeric keys(center of board), Cursor control keys (Right
hand side), Numeric keys, Escape keys.

23. Digitizer
 A digitizer consist of a flat operating surface, similar to a drawing board, under
which is mounted a fine grid of wires. It is provided with an electronic stylus.
When tip of stylus is touched at any point on the board the numeric identity of
that point is sent to the computers by means of electronic signal. As the stylus
moves on the digitizer board its movement is reflected on the screen.

24. Cursor Control Devices:
 The cursor normally takes the form of a bright spot on the CRT screen that
indicates where lettering or drawing will occur. The computer is capable of
reading the current position of the cursor. Hence the user's capability to control
the cursor position allows locational data to be entered into the CAD system
data base.
 There are a variety of cursor control devices which have been employed in
CAD systems. These include: Joysticks, Tracking ball, Mouse, Light Pen,
Thumbwheel, Electronic tablet etc.

25. Track Ball:
 It consists of a spherical ball of 50 mm in diameter which is mounted in small
flat box with exposed top as shown in Fig. Ball can be rotated in any direction
causes to move the cursor according to it. It is compact device & requires little
arm movement. The accuracy of the device is limited.

26. JoyStick:
 The joystick is a popular input devices used to locate the position of on screen.
It cursor consists of box with vertical joystick as shown in Fig. The device is
connected to the computer system by means of cable, which transmits
electronic signal corresponds to movement of joystick. Joystick can rotate in
any direction clockwise, anticlockwise, right or left causing cursor move
respective direction.

27. Mouse:
 The mouse is a small device used to point to a particular place on the screen
and select in order to perform one or more actions. It can be used to select
menu commands, size windows, start programs etc. The most conventional
kind of mouse has two buttons on top: the left one being used most frequently.
 Left Click: Used to select an item.
 Double Click: Used to start a program or open a file.
 Right Click: Usually used to display a set of commands.
 Drag and Drop: It allows you to select and move an item from one location to
another.

28. Light Pen:
 Light pen is a small rod-shaped device of the size and shape of felt-tip pen. It
is called light pen because of its property of detecting light. Pen consist of a
photocell sensory element which detects the presence of light and transmits
signal to graphic terminal. A light pen is used to direct contact with the screen.
Tip of pen is positioned by hand on CRT screen. Light pens are used for cursor
control & menu selection. It can also used for drawing image on screen.

29. Scanner:
 Scanner is an input device used for direct data entry from the source document
into the computer system. It converts the document image into digital form so
that it can be stored into the computer. Capturing information like this reduces
the possibility of errors typically experienced during large data entry.

30. Output Devices:

31. Visual Display Unit:
 It is also called as Monitor. It is an output device that resembles the television
screen and uses a Cathode Ray Tube (CRT) to display information. A Keyboard
is to use to Input data and Monitor is used to display the Input data and to
receive messages from the computer. It also displays the program or
application output. Like the television, monitors are also available in different
sizes.

32. Printer:
 Printers are used to produce paper (commonly
known as hardcopy) output. Based on the
technology used, they can be classified as Impact
or Non-impact printers.
 Impact printers use the typewriting printing
mechanism wherein a hammer strikes the paper
through a ribbon in order to produce output. Dot-
matrix and Character printers fall under this
category.
 Non-impact printers do not touch the paper while
printing. They use chemical, heat or electrical
signals to etch the symbols on paper. Inkjet,
Deskjet, Laser, Thermal printers fall under this
category of printers.

33. Plotter:
 Plotters are used to print graphical output on paper. It interprets computer
commands and makes line drawings on paper using multi-coloured automated
pens. It is capable of producing graphs, drawings, charts, maps etc.
 There are different types of plotters that are designed for different types of
application.
i. Ink jet Plotter.
ii. Drum Plotter.
iii. Flat bed Plotter

34. Graphics Software: Ground Rule
 The following are the ground rule that should be considered in designing graphics
software.
i. Simplicity: - The graphics software should be easy to use.
ii. Consistency: - The package should operate in consistence and predictable way to
use.
iii. Completeness: - There should be no inconvenient omission in the set of graphics
function.
iv. Robustness: - The system should be tolerant of minor instance of misuse by the
operator.
v. Performance: - Within limitation imposed by the system hardware, the performance
should be exploited as much as possible by software. Graphics programme should be
efficient and speed of response should be fast and consistent.

35. Graphics Software: General Requirement
 The following are the ground rule that should be considered in designing graphics
software.
 Generation of graphic primitives: The graphical primitives are 2D and 3D
geometrical elements. The 2D graphics primitives are point, line circle, ellipse,
Parabola & Hyperbola. The 3D graphics primitives are Cube, Sphere, Pyramid,
Cylinder and Cone & Torus. The graphics software should generate the basic
primitives and should also have a library of regularly used geometric features.
 Transformations: Transformation is Translation, Rotation, Scaling and Reflection.
These are used to modify the image on the display screen or to reposition the graphics
item in the database. These transformations help the user in constructing a
geometrical, model fast.
 Viewing/Display control and windowing: Views are defined by the various angles
from which a model can be observed. If the object is too complex to show it’s
entirely, windowing is used. An imaginary box is created around the position of the
object.

36. Graphics Software: General Requirement
 Segmenting: This function provides the user with the capability to selectively edit the
text such as deleting or modifying portions of the geometric model. This function is
responsible for dividing the total model into segment so that this segment can be
modified as well without affecting complex model. The term ‘Segment’ refers to
particular portion of the image which has been identified for purpose of modifying it.
The segment may be defined as single element or logical grouping of elements that
can be modified as a unit.
 User input functions: The user input functions should be accomplished to the
benefits of the interactive feature of interactive computer graphics. The functions
permit the user to enter commands or data into the system. The entry is accomplished
by means of operator input devices.

37. Geometric Transformation:
 All the changes performed on the graphics image are done by changing the
database of the original picture. These changes are called as transformation.
 Geometric transformation can be defined as “Changes done to the database by
performing certain mathematical operation on it, so as to produce the desired
change in the image”.
 Transformation can be used to effect the following changes in the geometric
object.
 Change the location
 Change the shape
 Change the size
 Rotate & copy the object
 Generate surface from a line
 Generate a solid from surface.

38. 2 D Transformation: Translation
 When every entity of a geometric model
remains parallel to its initial position, the
transformation is called as translation.
 Translating model means every point on it
moves by as equal given distance in a given
direction.
 A translating involves moving of an
element from one location to another.

39. 2 D Transformation: Rotation
 Rotation is an important transformation and
allows the user to view the object from different
angles.
 It can be used in the from of circular arrays, by
creating entity once & then rotate it to be desired
positions on the circumferences.
 Transformation such as translation, scaling &
reflection are cumulative.
 But rotation have unique property of it being non-
cumulative.
 Thus if two rotation are performed on the object,
the sequence of operation will alter the final
orientation of the object.

40. 2 D Transformation: Scaling
 Scaling alters the size of an object.
 Scaling can be uniform & non-uniform.
 Values of scaling factor grater than one increase the size of object whereas less
than one decrease the size of an object.
 When scaling factor are less than one , then object moves towards the origin.
 When scaling factor are greater than one, then object moves away origin.

41. 2 D Transformation: Reflection
 Reflection is the process of obtaining mirror of the original shape.
 This is an important transformation & used in may engineering products are
symmetrical.