Engineering Graphics (BT-105) Unit 6 Notes

How unit 6 is examined

This unit covers computer technologies for graphical communication (CAD, its advantages and limits, plotters) and the working theory of CAD software (zoom, dialog boxes, UCS icon, editing commands, layers); both topics carry high marks.

Listing the computer technologies that impact on graphical communication

High weight

Definition. CAD (Computer-Aided Design) is the use of computer systems to create, modify, analyse and optimise a design or drawing. Examples of CAD software are AutoCAD, SolidWorks, CATIA and Creo.

Key points.

Computer technologies that changed graphical communication are CAD software, input devices (keyboard, mouse, digitiser), output devices (monitor, printer, plotter) and digital storage and networks.
CAD replaces the drawing board, T-square and pencil with a screen, so drawings are made faster and more accurately.
Drawings are stored as digital files, so they can be saved, retrieved and shared by email or network in seconds.
CAD models can be passed to CAM (manufacturing) and CAE (analysis) software, so the same data drives production.
A plotter is an output device that draws large, accurate engineering drawings (A0, A1) using pens or inkjet heads, where an ordinary printer is too small.
Specifying a plotter means stating its bed or paper size, resolution in DPI, plotting speed, pen or inkjet type, and interface (USB, Ethernet, network) with a driver.
In CAD the plotter is then configured in the plot dialog: select the device, paper size, pen assignments and line widths, orientation, scale and plot area.

Advantages of CAD.

Productivity is higher and turnaround time shorter than manual drafting.
Accuracy is superior and human errors are reduced.
Editing and revision are easy, and standard blocks and templates are reused.
3D modelling and rendering give better visualisation.
Integration with CAM/CAE allows analysis and direct manufacture.
Storage, retrieval and digital sharing are convenient.

Disadvantages (limitations) of CAD.

High initial cost of software and hardware.
Trained operators are required.
Software updates and maintenance cost money.
Hardware failure, virus or power cut can cause data loss.

Answer frame. Open with the definition of CAD and name two packages (AutoCAD, SolidWorks); then give 5-6 advantages, each in one sentence, then 3-4 disadvantages; close with "CAD is preferred despite its cost because accuracy and speed outweigh it". For the plotter question, open with what a plotter is, list the specifications of point 6, then the CAD plot-dialog setup of point 7.

Asked: [7 marks] (Jun 2022, Dec 2023) What is CAD? Name two CAD softwares. Give advantages and disadvantages (limitations) of using CAD. Asked: [7 marks] (Jun 2022) How do you specify a plotter for graphics applications? Asked: [7 marks] (Nov 2022) Explain the various advantages of CAD.

Demonstrating knowledge of the theory of CAD software [such as: The Menu System, Toolbars, Drawing Area, Dialog boxes and windows, Shortcut menus, The Command Line, The Status Bar, Different methods of zoom, Select and erase objects, Isometric Views]

Definition. CAD software offers a graphical interface of menus, toolbars, dialog boxes, a drawing area, a command line and a status bar, through which drawings are created, viewed and edited.

Key points (interface).

The menu system (menu bar) groups commands such as File, Edit, View, Draw, Modify and Dimension; toolbars hold icon buttons for the same commands; shortcut (right-click) menus give context commands.
The drawing area is the blank canvas where the drawing is made; the command line accepts typed commands and prompts; the status bar shows coordinates and toggles (Snap, Grid, Ortho, Osnap).
Select and erase: objects are chosen by clicking, window or crossing selection, and the Erase command deletes them.

Zoom command. Zoom changes the magnification of the display only, and never the real dimensions of the drawing. It is used to see fine details and to navigate a complex drawing.

Option	Effect
All	Shows the drawing limits or extents, whichever is larger
Extents	Fills the screen with all objects drawn
Window	Enlarges a rectangular area picked by two corners
Dynamic	Pans and zooms with a movable view box
Previous	Returns to the last view
Realtime	Zoom in or out by dragging the mouse or wheel

Dialog boxes and windows. A dialog box is an interactive box for entering settings, e.g. Layer Properties, Dimension Style, Plot. Its components are text fields, drop-down lists, check boxes, radio buttons, preview areas and OK/Cancel buttons. Windows are the drawing window (model and paper space), command-line window, tool palettes and properties window. Dialogs are easier than typing because choices are visible and errors are fewer.

UCS icon. WCS is the fixed World Coordinate System; UCS is a movable User Coordinate System set by the user. The UCS icon shows the origin (0,0,0), the directions of X, Y, Z axes and the current XY working plane. It appears at the origin or at a corner (non-origin mode). UCSICON options are ON, OFF, Origin and NoOrigin.

Editing commands. Move, Copy, Trim, Extend, Offset, Mirror, Fillet, Rotate: type the command, select objects, give base and second point (Move, Copy) or the distance or angle.

Layers. Layers organise objects, each with its own colour, linetype and lineweight; they can be frozen or thawed, locked or unlocked, and switched on or off.

Isometric views. Isometric drawing mode (Isoplane, F5) sets the cursor axes at 30 degrees for isometric sketches.

Answer frame. Open with a one-line definition of the item asked; draw the Zoom option table, a sample dialog box or the UCS icon with axes; develop the components or options in the order above with one sentence each; close with its benefit (faster, accurate, clear drawing).

Pitfall: Zoom changes only the view size, not the object size; saying it scales the drawing loses marks.

Asked: [7 marks] (Jun 2022, Jun 2023) Explain the purpose of Zoom command. Asked: [7 marks] (Nov 2022, Jun 2025) Write about Dialog boxes and windows in CAD software. Asked: [7 marks] (Nov 2022) What is the use of UCS icon? Explain in detail. Asked: [14 marks] (Jun 2024) Write short notes (any two): i) Editing commands in CAD ii) Layering concept iii) Purpose of Zoom command

Last-minute revision

CAD is Computer-Aided Design; examples are AutoCAD, SolidWorks, CATIA, Creo.
CAD advantages: speed, accuracy, easy editing, 3D view, CAM/CAE link, easy storage.
CAD limits: high cost, training, updates, data loss.
Plotter specs: size, DPI, speed, pen or inkjet, interface.
Zoom changes the view only: All, Extents, Window, Dynamic, Previous, Realtime.
Dialog box parts: text field, drop-down, check box, radio button, preview, OK/Cancel.
UCS icon shows origin and X, Y, Z directions; UCSICON: ON, OFF, Origin, NoOrigin.
Editing: Move, Copy, Trim, Extend, Offset, Mirror, Fillet, Rotate.
Layer controls: colour, linetype, lineweight, freeze/thaw, lock/unlock, on/off.
Isometric mode uses 30 degree axes (F5).

Memory hooks

Zoom: "A E W D P R" = All, Extents, Window, Dynamic, Previous, Realtime.
CAD advantages: "SAFE 3D" = Speed, Accuracy, Fast editing, Easy storage, 3D.
UCS icon = a signpost showing origin and axis directions.
Layers = transparent tracing sheets stacked on each other.

Coverage checklist

listing the computer technologies that impact on graphical communication: plotter specification (Jun 2022), what is CAD with advantages and disadvantages (Jun 2022, Dec 2023), advantages of CAD (Nov 2022).
Demonstrating knowledge of the theory of CAD software [such as: The Menu System, Toolbars, Drawing Area, Dialog boxes and windows, Shortcut menus, The Command Line, The Status Bar, Different methods of zoom, Select and erase objects, Isometric Views]: Zoom (Jun 2022, Jun 2023), dialog boxes and windows (Nov 2022, Jun 2025), UCS icon (Nov 2022), short notes on editing, layers, zoom (Jun 2024).

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Engineering Graphics (BT-105) - Unit 6 Short Notes