CAD (COMPUTER AIDED DRAFTING)



              CAD (COMPUTER AIDED DRAFTING)


          It is the application of conventional computer techniques with the aid of data processing systems to present a graphical solution.

          It deals with the creation, storage and manipulation of models of objects and pictures via computer

COMMAND AREA:

           It is ear marked at the bottom of the screen and the commands may be entered in this area by key boards to achieve communication with the computer.

SCREEN MENU AREA:

             It is the area on the right hand side of the screen. This command can be selected by key board/mouse/digitizer.

STATUS LINE AND MENU BAR AREA:

                This is available at the top of the screen and commands may be entered from with the help of pull down menu.


DRAWING AREA:


This is the central portion of the screen where the entities may be drawn by interaction with computer.

Auto cad releases 14windows version. It has a set of drop down windows for various menu options.


PLANNING FOR A DRAWING:


While planning a drawing in auto cad one has to organize some of the information such as choosingthe units, co-ordinate system etc…

CO-ORDINATE SYSTEM:


The system used by all the CAD packages is generally rectangular Cartesian co-ordinates system designated as x, y and z axis. The positive direction of these are follows the right hand rule.

The co-ordinates system can be input into the system by

The direct input of co-ordinate values in the respective order of x, y & z. 

Specifying the co-ordinates in an incremental format from the current cursor position in the drawing area. The distance is specified by using @ parameter before the actual values. 

Point co-ordinates may also be specified using the polar co-ordinates format. 

Use the mouse button the cursor may be taken into required position and button is clicked. Getting started with Auto –CAD 

1. Switch on the computer 
2. Windows screen will appear on the desk top 
3. On the screen find the Auto-CAD 14”Icon of the rectangular area expressed in x, y co-ordinates 

DRAWING LIMITS:

Thedrawinglimits are the borders of the rectangular area expressed in x, y co-ordinates.

COMMAND: Limits Lower left corner :0,0 
Upper right corner:(12,9) default 

After settings the limits of the drawing the following drawing Aid’s /tools may be used to locate specific points on the screen. 

ORTHO COMMAND:


This is orthogonal drawing mode. This command constrains the lines are drawn in horizontal and vertical direction only

Command: ORTHO press enter

ON/OFF <current>ON ENTER

SNAP COMMAND:

This is used to set increments for cursor movement

Command: SNAP press enter

ON/OFF/ASPECT/LOCATE/STYLE<current>:0.1default ENTER

GRID COMMAND:

This command is used to set the drawing area into graph function keys:

F7 forGRID ON/OF
F8 forORTHO ON/OF
F9 for SNAPON/OF


HELP COMMANDS:

Auto-cad provides withcomplete help at any point of working in the program.

TYPES OF ENTITIES:

POINT: This command is used to locate point in the drawing.

Command: POINT and press enter
Start of point (25, 45) enter
Apoint is placed at given location

LINE: 

Line can be constrained to horizontal/vertical by ORTHO command Command: line enter


Start point: 10, 20 enter

To point: 40, 20 enter
To point: 40, 60 enter
To point: 10, 60 enter
To point: pressenter

It is also be possible to specify the co-ordinates in incremental format as distance from the current cursor position in the drawing

Command: line enter From point: 10, 20 enter To point: @40, 0 enter To point: @-20, 30 enter To point: 10,20enter

To point: press enter

It is possible to specify the point co-ordinate using the polar co-ordinates

Command: line enter

From point: 10, 20 enter

To pint: @30<0 enter
To pint: @30<60 enter
To pint: @30<20 enter

To pint: @30<180 enter

To pint: @30<240 enter

To pint: 10, 20 enter

To pint: press enter

CIRCLE:It is an entity to draw circular objects (or) sections Command: circle enter


1. 3P/2P/PTR/<center point> c enter 0,0 enter Diameter /<radius>/<current default>: select D or R

2. 3P(option) one is promoted for a first, second and third point the circle will be drawn to pass through these points. 

3. 2P(2point/option): one is promoted for the selection of two points which forms the opposite ends of diameter. 

4. TTR option: allows one to define a circle based on two tangent points with radiu. The tangent points can be lines, arc’s or circles 

ELLIPSE:It is an entity to draw ellipse or egg shaped objects.


1. Command: ellipse enter <Axis end point1> center point: Axis end point: 0, 0 

Axis end point: 0, 0 
<Other axis distance>/radius: 25 
2. Command: ellipse enter 
<Axis end point1>center: C enter 
This command is used to one center point and one end point of each axis should be provided. 

POLYGON: It is an entity to draw more than 3 sides in a number of ways

Command: polygon enter

Number of sides <4>:8 enter
Edge /<center of polygon>:100,120 enter
Inscribed/circumscribed about a circle (I /C): I or C enter

Radius of circle: 80

Command: polygon enter
Number of sides: 7 enter
Edge/<center of polygon>: Eenter
First end point: 15, 15 enter
Second end point: 15, 30 enter


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