TABLE OF CONTENTS

TITLE

ACKNOWLEDGEMENT

INTRODUCTION OF CAD

INTRODUCTION OF CAD SOFTWARE

HISTORY

USES

TYPES OF COMMANDS

DRAWING FILES

ACKNOWLEDGEMENT

I wish to express my deep sense of gratitude to my Internal Guide, ER.

Avtar Singh Bhullar for his able guidance and useful suggestions,

which helped me in completing the CAD Lab work , in time.

Finally, yet importantly, I would like to express my heartfelt thanks to

my beloved parents for their blessings, my friends/classmates for their

help and wishes for the successful completion of this work.

INTRODUCTION OF CAD

Throughout the history of our industrial society, many inventions have

been patented and whole new technologies have evolved. Perhaps the

single development that has impacted manufacturing more quickly and

significantly than any previous technology is the digital computer.

Computers are being used increasingly for both design and detailing of

engineering components in the drawing office. Computer-aided design

(CAD) is defined as the application of computers and graphics software

to aid or enhance the product design from conceptualization to

documentation. CAD is most commonly associated with the use of an

interactive computer graphics system, referred to as a CAD system.

Computer-aided design systems are powerful tools and in the

mechanical design and geometric modeling of products and components.

There are several good reasons for using a CAD system to support the

engineering design function:

· To increase the productivity

· To improve the quality of the design

· To uniform design standards

· To create a manufacturing data base

· To eliminate inaccuracies caused by hand-copying of drawings and

inconsistency between drawings

INTRODUCTION OF CAD SOFTWARE

Computer-aided design (CAD), also known as computer-aided

design and drafting (CADD) is the use of computer technology for the

process of design and design-documentation. Computer Aided Drafting

describes the process of drafting with a computer. CADD software, or

environments, provides the user with input-tools for the purpose of

streamlining design processes; drafting, documentation, and

manufacturing processes. CADD output is often in the form of electronic

files for print or machining operations. The development of CADD-

based software is in direct correlation with the processes it seeks to

economize; industry-based software typically uses vector-based

environments whereas graphic-based software utilizes raster-based

environments.

CAD environments often involve more than just

shapes. As in the manual drafting of technical and engineering drawings,

the output of CAD must convey information, such as materials,

processes, dimensions, and tolerances, according to application-specific

conventions.

CAD may be used to design curves and figures

in two-dimensional (2D) space; or curves, surfaces, and solids in three-

dimensional (3D) objects

HISTORY

Designers have long used computers for their calculations. Initial

developments were carried out in the 1960s within the aircraft and

automotive industries in the area of 3D surface construction and NC

programming, most of it independent of one another and often not

publicly published until much later. Some of the mathematical

description work on curves was developed in the early 1940s by Robert

Issac Newton from Pawtucket, Rhode Island. Robert A. Heinlein in his

1957 novel The Door into Summer suggested the possibility of a

robotic Drafting Dan. However, probably the most important work on

polynomial curves and sculptured surface was done by Pierre

Bézier (Renault), Paul de Casteljau (Citroen), Steven Anson

Coons (MIT, Ford), James Ferguson (Boeing), Carl de Boor(GM),

Birkhoff (GM) and Garibedian (GM) in the 1960s and W. Gordon (GM)

and R. Riesenfeld in the 1970s.

It is argued that a turning point was the development of

the SKETCHPAD system at MIT in 1963 by Ivan Sutherland (who later

created a graphics technology company with Dr. David Evans). The

distinctive feature of SKETCHPAD was that it allowed the designer to

interact with his computer graphically: the design can be fed into the

computer by drawing on a CRT monitor with a light pen. Effectively, it

was a prototype of graphical user interface, an indispensable feature of

modern CAD.

The first commercial applications of CAD were in large companies in

the automotive and aerospace industries, as well as in electronics. Only

large corporations could afford the computers capable of performing the

calculations. Notable company projects were at GM (Dr. Patrick

J.Hanratty) with DAC-1 (Design Augmented by Computer) 1964;

Lockheed projects; Bell GRAPHIC 1 and at Renault (Bézier) –

UNISURF 1971 car body design and tooling.

One of the most influential events in the development of CAD was the

founding of MCS (Manufacturing and Consulting Services Inc.) in 1971

by Dr. P. J. Hanratty, who wrote the system ADAM (Automated

Drafting And Machining) but more importantly supplied code to

companies such as McDonnell

Douglas (Unigraphics), Computervision (CADDS), Calma, Gerber,

Autotrol and Control Data.

As computers became more affordable, the application areas have

gradually expanded. The development of CAD software for personal

desktop computers was the impetus for almost universal application in

all areas of construction.

Other key points in the 1960s and 1970s would be the foundation of

CAD systems United Computing, Intergraph, IBM, Intergraph IGDS in

1974 (which led to Bentley Systems MicroStation in 1984)

CAD implementations have evolved dramatically since then. Initially,

with 3D in the 1970s, it was typically limited to producing drawings

similar to hand-drafted drawings. Advances in programming and

computer hardware, notably solid modeling in the 1980s, have allowed

more versatile applications of computers in design activities.

Key products for 1981 were the solid modelling packages -

Romulus (ShapeData) and Uni-Solid (Unigraphics) based on PADL-2

and the release of the surface modeler CATIA (Dassault Systemes).

Autodesk was founded 1982 by John Walker, which led to the 2D

system AutoCAD. The next milestone was the release

of Pro/ENGINEER in 1988, which heralded greater usage of feature-

based modeling methods and parametric linking of the parameters of

features. Also of importance to the development of CAD was the

development of the B-rep solid modeling kernels (engines for

manipulating geometrically and topologically consistent 3D

objects) Parasolid (ShapeData) and ACIS (Spatial Technology Inc.) at

the end of the 1980s and beginning of the 1990s, both inspired by the

work of Ian Braid. This led to the release of mid-range packages such

as SolidWorks in 1995, Solid Edge (then Intergraph) in 1996

and Autodesk Inventor in 1999

USES

CAD is also used for the accurate creation of photo simulations that are

often required in the preparation of Environmental Impact Reports, in

which computer-aided designs of intended buildings are superimposed

into photographs of existing environments to represent what that locale

will be like were the proposed facilities allowed to be built. Potential

blockage of view corridors and shadow studies are also frequently

analyzed through the use of CAD.

CAD has also been proven to be useful to engineers as well. Using four

properties which are history, features, parameterization, and high level

constraints (Zhang). The construction history can be used to look back

into the model's personal features and work on the single area rather than

the whole model (zhang). Parameters and constraints can be used to

determine the size, shape, and the different modeling elements. The

features in the CAD system can be used for the variety of tools for

measurement such as tensile strength, yield strength, also its stress and

strain and how the element gets affected in certain temperatures.

Computer-aided design is one of the many tools used by engineers and

designers and is used in many ways depending on the profession of the

user and the type of software in question.

TYPES OF COMMAND

Units: This command is used first in C A D before starting the

drawing. In this we set length type, length precision, angle

type, angle precision, insertion scale etc.

Dimension : In this command we use following dimensions:-

a. Linear

b. Aligned

c. Arc length

d. Radius

e. Diameter

f. Angular

a. Linear: It gives the dimension of length.

b. Aligned: It gives the dimension of aligned length.

c. Radius: It gives the dimension of radius of circle.

d. Arc length: It gives the dimension for arc.

e. Diameter: It gives the dimension of diameter of circle.

f. Angular: It gives the angle dimension.

3. Dimension style: This command is used to set the

dimensions. It contain following terms :

a. Set Current

b. New

c. Modify

d. Override

e. Compare

a. Set Current: This is used to change the dimension of

current drawing.

b. New: This is used to change the dimension of new

drawing.

c. Modify: This used to set the dimensions of Line, Symbol

& Arrows, Text, Fit, Primary Units, Alternate Units,

Tolerances.

d. Override: Override current style:-

e. Compare: This command is used for comparision.

Plot: This command is used to convert drawing file DWG to

PDF.

Line

To use the AutoCAD line command, first make sure that the draw toolbar is

shown. Click the line command on the draw toolbar. The command line will ask

you to specify the first point. Click in the drawing area. Move the mouse to another

place in the drawing area and click again. This will draw your first line. Move your

mouse to another position in the drawing area and click again. This will draw

another line, which is connected to the last point of your first line. You can

continue making lines like this in AutoCAD® until you tell it to stop. To tell

AutoCAD® to stop making lines, press the Enter key. If you would like to have

your last line connect back to your first line (like if you wanted to make a closed

box), then do not press the Enter key but right-click,

POLYGON

This AutoCAD tutorial covers how to draw a polygon by specifying the number of

sides, then specifying the radius from the center to a corner or to a flat part of the

polygon

Rectangle

The AutoCAD rectangle tutorial shows how to draw a rectangle anywhere on the

screen and make the base and height of the rectanlge a specified dimension. The

tutorial then shows how to label these sides with their lengths.

Circle

   

This AutoCAD tutorial describes how to draw a circle by either a specified

radius or a specified diameter. The lesson then goes on to explain how to modify

the circle and change its size by specifying an area or a circumference. The

tutorial teaches a little about the command line and is the perfect way to get

started drawing objects of exact sizes and specifications using Auto

Ellipse

   

This AutoCAD ellipse tutorial teaches several methods of creating and

modifying ellipses. First it describes what an ellipse is besides just an oval. It

demonstrates how AutoCAD® can create an ellipse based on either a radius or

diameter. The tutorial goes on to show how to create a partial ellipse based on

an angle. It also teaches how to modify an ellipse by the properties box or by

clicking on it to move/resize it.

Revision Cloud: Creates a revision cloud using a polyline

You can create a new revision cloud by dragging your cursor,

or you can convert a closed object such as an ellipse or

polyline into a revision cloud. Use revision clouds to

highlight parts of a drawing that arc being reviewed

Spline: Creates a smooth curve that passes through or near specified

points

You can control the maximum distance between the B-spline curve and

the fit points, shown in the illustration, by changing the value for the fit

tolerance with SPLINEDIT. You can also display the control frames for

B-splines with SPLFRAME.

Ellipse: Creates an ellipse or an elliptical arc

The first two points of the ellipse determine the location and

length of the first axis. The third point determines the distance

between the center of the ellipse and the end point of the second

axis.

Ellipse Arc: Creates an elliptical arc

The first two points of the elliptical arc determine the

location and length of the first axis. The third point

determines the distance between the center of the elliptical

arc and the endpoint of the second axis. The fourth and fifth

points are the start and end angles.

Point: Creates multiple point objects

You can use MEASURE and DIVIDE to create points along

an object. Use DDPTYPE to specify point size and styles

easily.

Hatch: Fills an enclosed area or selected objects with a hatch pattern or

fill

You can choose from several methods to specify the

boundaries of a hatch.

- Specify a point in an area that is enclosed by objects.

- Select objects that enclose an area.

- Drag a hatch pattern into an enclosed area from a tool

palette or Design Center.

Table: Creates an empty table object

A table is a compound object that contains data in row and

column. It can be created from an empty table or a table

style. A table can also be linked to data in a Microsoft Excel

spreadsheet.

Multiline Text: Creates a multiline text object

You can create several paragraphs of text as a single

multiline text (mtext) object. With the built-in editor, you can

format the text appearance, columns, and boundaries.

Erase: Removes objects from a drawing

Instead of selecting objects to erase, you can enter an option,

such as L to erase the last object draw, p to erase the

previous selection set, or ALL to erase all objects. You can

also enter ? to get a list of all options.

Copy: Copy objects a specified distance in a specified direction

With the COPYMODE system variable, you can control

whether multiple copies are created automatically.

Mirror: Creates a mirrored copy of selected objects

You can create objects that represent half of a drawing, select

them, and mirror them across a specified line to create the

other half.

Offset: Creates concentric circles, parallel lines, and parallel curves

You can offset an object at a specified distance or through a

point. After you offset objects, you can trim and extend them

as an efficient method to create drawing containing many

parallel lines and curves.

Array: Creates multiple copies of objects in a pattern

You can create copies of objects in a regularly spaced

rectangular or poplar array. Array are following type

a. Rectangular array

b. Polar array

a. Rectangular array: In this first select the object then fill the

number of row and colums.

b. Polar array: In this first select the object then fill the total

number of items and angle to fill.

Move: Moves objects a specified distance in a specified direction

Use coordinates, grid snaps, object snaps, and other tool to

move objects with precision.

Rotate: Rotates objects around a base point

You can rotate selected objects around a base point to an

absolute angle.

Scale: Enlarges or reduces selected objected, keeping the proportions of

the object the same after scaling

To scale an objects, specify a base point and a scale factor.

The base point acts as the center of the scaling operation

and remains stationary. A scale factor greater than 1

enlarges the object. A scale factor between 0 and 1 shrink

the objects.

Trim: Trims objects to meet the edges of other objects

To trim objects, select the boundaries. Then press ENTER

and select the objects that you want to trim. To use all

objects as boundaries, press ENTER at the first Select

objects prompt.

Chamfer: Bevels the edges of objects

The distance and angle that you specify are applied in the

order that you select the objects.

Fillet: Rounds and fillets the edges of objects

In the example, an arc is created that is tangent to both of

the selected lines. The lines are trimmed to the ends of the

arc. To create a sharp corner instead, enter a radius of zero.

OBJECT SNAPS (OSNAP):

OSNAPs allows you to select positions on components in a drawing for locating

other features.

You can select Osnaps by:

clicking on the tool button icon (see above)

typing an Osnap alias on the prompt line when needed

When an Osnap is used, the CURSOR changes shape when it is near a position

that matches the Osnap selected and "snaps" to that point. The cursor shape differs

with each Osnap.

OSNAP Commands and typed abbreviations:

Osnap

type

Typed

Command

and Use

Center

cen

Snaps to the center of a circle or arc. Click the left mouse button when

the cursor is on the edge of the circle or arc you wish to use.

End-

point

end

Snaps to the endpoint of a line, polyline, or arc. Place the cursor over

the specific end of the entity you wish to snap to and click the left mouse

button.

Insert

ins

Locates the insertion point of text or a block. Place the cursor anywhere

on the block or line of text and click the left mouse button.

Inter-

section

int

Allows you to select the intersection between two items. Place the

locating square over the intersection and click with the left mouse

button.

Midpointmid

Snaps to the midpoint of a line or arc. Click near the entity's midpoint.

Nearest

nea

Locates the point or entity nearest the cursor position. Place the cursor

near the item you wish to select and click the left mouse button.

Node

nod

Snaps to a point entity. You must position the cursor square so that it

contains the point and click with the left mouse button.

Perpen- per

dicular This option locates a perpendicular point on an adjacent entity. It will

only function as the second location in a command. Place the cursor on

a line or straight pline segment near the perpendicular location and

click with the left mouse button.

Quadrant

qua

Locates the 0, 90, 180, or 270 degree position (quadrants) of a circle.

Place the cursor near the quadrant point and click the left mouse button

when the cursor changes shape.

Tangent

Tan

Places an entity at the tangent point of an arc or circle. Place the cursor

on the arc or circle as near as possible to the expected tangent point and

click the left mouse button.

s