Graphic CommunicationGraphic Communication

CAD/CAG Revision

ComputerComputer HardwareHardware

• Processor

• Input Devices

• Output Devices

• Storage Devices

CPUCPUCentral Processing UnitCentral Processing Unit

The computers ‘Brain’ A large micro chip

that controls the computer and carries out all the instructions and data handling

Computer HardwareComputer Hardware

Input Devices

KeyboardKeyboard

Used to input text and numbers into the computer

Esc F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12

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!1

@2

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%5

^6

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*8

(9

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Q W E R T Y

A S D F G H

Z X C V B

U I O P

J K L

N M

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Tab

Shift

Ctrl Alt

CapsLock

Alt Ctrl

Shift

Enter

Backspace Insert Home PageUp

Delete End PageDown

|\

7 8 9

4 5 6

1 2 3

0 .

NumLock

Home PgUp

End PgDn

Ins Del

Enter

/ *

+

PrintScreen

ScrollLock Pause

ScrollLock

CapsLock

NumLock

MouseMouse

Used to guide a pointer or cursor around the screen.

Functions are selected with the aid of the control buttons

Some mice have a wheel which is used for zoom and scrolling

Tracker BallTracker Ball

This device is very similar to a mouse.

It is used where there is little desk space available for a mouse

The large ball is on the top of the device and is rotated using the palm of the hand

JoystickJoystick

Used commonly for games

Used in many simulation situations. E.g. Flight and tank simulators

Graphics TabletGraphics Tablet

Used for sketching or tracing drawings into a computer

Uses a puck or a pen to detect the exact position of the cursor on a drawing etc.

Digital Stills CameraDigital Stills Camera

This camera stores the pictures it takes in digital form. These can the be downloaded to a computer for inclusion in a DTP document etc.

ScannerScanner

Used to electronically convert paper images to to computer files.

Text can be scanned in using OCR (Optical

Character Recognition) software

Flat bed Scanner

Hand held Scanner

Computer HardwareComputer Hardware

Output Devices

Flatbed PlotterFlatbed Plotter

Only used by CAD programs

Produces line drawings

Page size is limited by size of plotter bed

Not suitable for printing pictures

Drum PlotterDrum Plotter

Drum plotter are usually used in industry to produce large drawings (up to A0)

Paper moves back and forwards while pen moves from side to side

Fax/ModemFax/Modem

A modem is both an input and output device

Data can be exchanged with drawing offices across the world electronically

Storage DevicesStorage Devices

A PC usually has several methods of storing data on it. These may include a mixture of fixed and removable storage systems

Floppy DiscFloppy Disc

Portable removable storage

Only holds 1.44 MB of data

Can be used in most computer systems

Easily damaged

Hard DriveHard Drive

Large capacity storage Not portable – build

into base unit of computer

Fast saving and retrieval of data

Zip DiscZip Disc

Similar to floppy disc but greater storage capacity (100 – 250 MB)

Portable Not all computers

have Zip drives

CD RomCD Rom

High capacity portable storage

Needs a CD writer to store data

CAD CommandsCAD Commands

You must know for your exam the following common CAD commands

CAD Commands 1CAD Commands 1

An on screen grid which can be set to any size. Can make it easier to do orthographic drawings

An on screen grid which is set at 30 deg. Can make it easier to do Isometric drawings

CAD Commands 2CAD Commands 2

This restricts the start and end points of lines to a predefined grid

This allows different types of information to be keep separate on a drawing

CAD Commands 3CAD Commands 3

Allows a user to increase or decrease the screen view so that they can see more detail

Allows the drawing of rectangular shapes on screen

CAD Commands 4CAD Commands 4

Allows the user to draw arcs and circles on screen

Allows the user to copy and position objects or parts of a drawing without having to redraw them

CAD Commands 5CAD Commands 5

This allows the user to draw circular or rectangular arrangements from a single object

Fillet puts a radius on a corner (rounded)

Chamfer puts a 45 deg angle on a corner

CAD Commands 6CAD Commands 6

Trim/Break removes an unwanted section of line, etc.

Extend makes a line, etc. longer (usually to meet another object)

This allows the user to turn an object at any angle about a point

CAD Commands 7CAD Commands 7

This allows the user to change the size of an object

This flips an object about the horizontal or vertical axis

Storage and retrieval

A completed drawing or series of drawings can be stored on hard drive, floppy disc, Zip disc or CD-R. These formats require less storage space than paper drawings. The drawings can then be printed as many times as required with no deterioration in quality.

 

Ease of modification

Companies who use CAG systems have advantages over competitors who rely on more traditional methods of modifying drawings. The ease and speed with which modifications can be made reduce time and costs, which in turn increases productivity.

 

Repetitive elements (library)

Drawings can contain a number of repetitive elements such as doors, windows, kitchen fittings and appliances. It is useful to have these items stored in a CAD library file. CAD library files are available for mechanical engineering, architecture and electronics. Items that you design need only be drawn once, saved to a library file, then retrieved and positioned each time they are required on a drawing. This saves time and effort, which increases productivity.

 

ADVANTAGES OF A CAG SYSTEM OVER A DRAWING BOARD 1

ADVANTAGES OF A CAG SYSTEM OVER A DRAWING BOARD 2

Drawing speed

It does take a considerable amount of time and financial investment by companies to train their CAG operators. In relative terms, however, drawing production is much faster using CAG than using traditional methods, so the company will save time and money in the long run.

 

Standardisation of drawings

Standardisation of drawings is often determined by drawing standards such as 851. Standardisation of drawing layouts and styles can easily be created in the 'in-house' or corporate style adopted by the operator or the company.

 

Drawing size and flexibility

Drawings can be enlarged or reduced with no loss of detail. Extremely fine, detailed work can be produced using commands such as ZOOM. Positive location tools such as GRID, GRID SNAP and ATTACH enable accuracy to be maintained even in the smallest details.