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MALAYSIA
POLYTECHNICS
MINISTRY OF EDUCATION
MODULE E 2004
COMPUTER AIDED DESIGN
IDRIS BIN KAMARUDDIN (PSA)
BIODATA OF MODULE WRITERS
E2004 COMPUTER AIDED DESIGN
Name : Idris Bin Kamaruddin
Address : Electrical Engineering Department Politeknik Sultan Salahuddin Abdul
Aziz Shah, Persiaran Usahawan,
Seksyen U1, 40150 Shah Alam, Selangor.
Telephone No. : 03-55691901 ext.6020 e-mail : [email protected] / [email protected]
Qualifications : B.Eng Electrical ( Mechatronic )– (UTM)
Position : Lecturer
Name : Shaliza Bt Shahril
Address : Electrical Engineering Department Politeknik Sultan Salahuddin Abdul
Aziz Shah, Persiaran Usahawan,
Seksyen U, 40150 Shah Alam, Selangor.
Telephone No. : 03-55691901 ext.6020 e-mail : [email protected]
Qualifications : Diploma Electrical Engineering &
Education.( ITTHO- UTM )
Position : Polytechnic Lecturer
PROOF READER
Name : Khairul Bariah Bt Takrim
Address : No.2, Lorong Sungai Isap Damai 8,
2515, Kuantan, Pahang.
( Politeknik Sultan Ahmad Shah ) Telephone No. : 019-9672922
e-mail :
Qualifications : MA TESL, BA Linguistics Position : Lecturer
What Do You Think Of This Module?
Title of Module: _______________________ Module Code : ___________
Student’s Name: _______________________ Registration No. : ___________
Course : ____________________________________
Module Writers: ______________________________
Please use the following scale for your evaluation:
4 Strongly Agree 3 Agree 2 Disagree
1 Strongly Disagree
Instruction : Please √ on the space provided.
No. How much do you agree with the following statements? SCALE
A. FORMAT 1 2 3 4
1 The pages are organized in an interesting manner. 2 The font size makes it easy for me to read the module.
3 The size and types of pictures and charts used are suitable for the input.
4 The pictures and charts are easy to read and understand. 5 The tables used are well-organised and easy to understand. 6 The arrangement of the Input makes it easy for me to follow. 7 All the instructions are displayed clearly.
B. CONTENTS 1 2 3 4
8 I understand all the objectives clearly. 9 I understand the ideas conveyed.
10 The ideas are presented in an interesting manner. 11 All the instructions are easy to understand.
12 I can carry out the instructions in this module. 13 I can answer the questions in the activities easily. 14 I can answer the questions in the self-assessment. 15 The feedback section can help me identify my mistakes. 16 The language used is easy to understand.
17 The way the module is written makes it interesting to read. 18 I can follow this module easily.
19 Each unit helps me understand the topic better.
20 I have become more interested in the subject after using this module.
CURRICULUM GRID
The curriculum grid of this module is based on the curriculum used by Malaysian polytechnics.
No. TOPIC UNIT Total
Hours 1 Introduction To CAD 1 3 2 Methods to Entering Command and Data Input 2 6 3 Drawing Aids, Drawing Limits and Display Control 3 3 4 Draw Command 4 9 5 Modify Command 5 6 6 Text,Dtext and Textstyles 6 6 7 Dimensioning 7 3 8 Linetype, Layer and Block 8 3 9 Printing 9 3
UNIT 1 INTRODUCTION TO CAD
1.1 Introduction
1.1.1 CAD Definition 1.1.2 Systems requirement
1.1.3 The list of other CAD packages 1.1.4 Advantages of using CAD
1.2 Getting started
1.2.1 Introducing CAD for windows.
UNIT 2 METHODS TO ENTERING COMMAND AND DATA INPUT
1.1 How to begin command
1.2 Creating drawing by using Coordinate Entry.
UNIT 3 DRAWING AIDS, DRAWING LIMITS AND DISPLAY CONTROL
3.1 Describing drawing aids command: 3.1.1 Snap
3.1.2 Ortho 3.1.3 Grid
3.1.4 Object Snap
3.2 Drawing Limits setup.
3.3 Explaining display control and others display commands 3.3.1 Zoom
3.3.2 Pan 3.3.3 Redraw 3.3.4 Regen
UNIT 4 DRAW COMMANDS
4.1 Identifying the specification of draw commands. 4.1. 1 Lines
4.1. 3 Circles 4.1. 4 Ellipse 4.1. 5 Polygon 4.1. 6 Point 4.1. 7 Polyline 4.1. 8 Solid 4.1. 9 Donut
4.2 Drawing simple electronics component, schematic and PCB diagram by using draw commands.
UNIT 5 MODIFY COMMANDS
5.1 Describing the using of edit commands 5.1.1 Erase 5.1.2 Move 5.1.3 Rotate 5.1.4 Trim 5.1.5 Scale 5.1.6 Mirror 5.1.7 Array 5.1.8 Stretch 5.1.9 Extend 5.1.10 Fillet 5.1.11 Chamfer 5.1.12 Offset 5.1.13 Divide 5.1.14 Measure 5.1.15 Change 5.1.16 Pedit
UNIT 6 TEXT, DTEXT AND TEXTSTYLES
6.1 Describing TEXT and DTEXT command. 6.1.1 Justify Text
UNIT 7 DIMENSIONING
7.1 Benefit of using dimension.
7.2 Describing of Dim Style and Dimupdate 7.3 Types of dimension. 7.3.1 Linear 7.3.2 Aligned 7.3.3 Angular 7.3.4 Diameter 7.3.5 Radius
UNIT 8 LINETYPE, LAYER AND BLOCK
8.1 Type of line regarding with drawing needed. 8.1.1 Load and setting type of lines
8.2 Layer
8.2.1 Introduction of Layer 8.2.2 Layer Commands
8.2.3 Layer Control by using dialog box 8.2.4 Create a drawing after layer setting.
8.3 Block and Wblock
8.3.1 Describing of block and Wblock, insert, Minsert, explode, and attribute.
UNIT 9 PRINTING
9.1 Printing Command 9.2 Print / Plot Configuration
MODULE GUIDELINES
To achieve maximum benefits in using this module, students must follow the instructions carefully and complete all the activities.
1. This module is divided into 16 units.
2. Each page is numbered according to the subject code, unit and page number.
E2004 / UNIT 1 / 5
Subject Unit 1 Page Number 5
3. The general and specific objectives are given at the beginning of each unit. 4. The activities in each unit are arranged in a sequential order and the
following symbols are given:
OBJECTIVES
The general and specific objectives for each learning topic are stated in this section.
INPUT
This section introduces the subject matter that you are going to learn.
ACTIVITIES
The activities in this section test your understanding of the subject matter. You have to complete this section by following the instructions
FEEDBACK
SELF-ASSESSMENT
Self-assessment evaluates your understanding of each unit.
FEEDBACK OF SELF-ASSESSMENT
This section contains answers to the activities in the self-assessment. .
5. You have to follow the units in sequence.
6. You may proceed to the next unit after successfully completing the unit and you are confident of your achievement.
GENERAL AIMS
This module is prepared for students in the second semester who are following the Certificate/Diploma programmes in Malaysian Polytechnics. It aims to expose students to the Computer Aided Design concept in each unit and to lead them towards self-directed learning or with guidance from their lecturers.
PREREQUISITE SKILLS AND KNOWLEDGE
The prerequisites of this module is at least a pass in SPM.
GENERAL OBJECTIVES
At the end of this module, students should be able to:
1. Describe the CAD definition, system requirement and advantage of using CAD. 2. Get started with AutoCAD.
3. Enter command and data input
4. Use draw command to make simple drawing. 5. Use draw aids command to make drawing easier. 6. Learn to use draw limits.
7. Learn to use important editing command. 8. Use display control.
9. Learn how to place text on a drawing. 10. Learn how to use dimensioning. 11. Use linetype in the drawing.
12. Learn how to use layer to control display of the drawing. 13. Learn to make and insert blocks.
14. Set the printing to print drawing.
TEACHING AIDS AND RESOURCES NEEDED
1. Computer
1. James A.Leach ( 1998 ) – AutoCAD 14 Instructor; McGraw Hill Company.
2. KnowledgeworksTM ( 1998 ) – AutoCAD R14 Fundamentals; Autodesk Press
3. Alan J.Kalameja ( 1995 ) – The Autocad Tutor For Engineering
Graphics-Release 12 and 13; Autodesk Press.
4. Bill Burehard, David Pitzer, Francis Soen ( 1998 ) – Inside Autocad 14, Limited Edition; New Rider Publishing, Indianapolis, Indiana.
5. Alan T.H Khoo ( 2002 ) – Step by Step AutoCADLT, Volume 1: The
UNIT 1
INTRODUCTION TO CAD
OBJECTIVES
General Objective : To understand the function of CAD and how to begin using AutoCAD
Specific Objectives : At the end of the unit you should be able to:
¾ Explain CAD.
¾ Identify system requirement needed to run the CAD program. ¾ List other CAD packages.
¾ Explain the advantages of using CAD compared to conventional drawing.
¾ Start AutoCAD to begin drawing. ¾ Use menus, dialog box and toolbars. ¾ Save and exit from AutoCAD drawing.
INPUT 1a
1.0 DEFINITION OF CAD
CAD is an acronym for Computer Aided Design or Computer Aided Drafting. CAD allows you to accomplish design and drafting activities using a computer. We can use CAD to draw a building plan, circuit diagram, chart, 3D object and more.
Design is a broad field involving the process of making ideas into a real product or system. The design process requires repeated refinement of ideas until a solution results – a manufactured product or constructed system. Traditionally, design involves the use of sketches, drawings, renderings, 2-dimensional and 3-dimensional models, prototypes, testing, analysis, and documentation. Drafting is generally known as the production of drawing that is used to document a design for manufacturing or construction or to archive the design.
CAD is a tool that can be used to design and draft activities. CAD can be used to make “rough” ideas drawing, although it is more suited to create accurate finished drawing and rendering. CAD can be used to create a 2-dimensional or 3-dimensional computer model or system for further analysis and testing by other computer programs. In addition, CAD can be used to supply manufacturing equipment such as lathes, mills, laser cutter, or rapid prototyping equipment with numerical data to manufacture a product. CAD is also used to create the 2-dimensional documentation drawing for communicating and archiving the design.
The tangible result of CAD activity is usually a drawing generated by a plotter or printer but can be a rendering of a model or numeric data in binary usually saved to magnetic or optical device such as a diskette, hard disk, tape or CD.
1.1 SYSTEM REQUIREMENT.
The following list consists of recommended hardware and software required for proper operation using CAD software.
• Windows NT 3.51 or 4.0 or Windows 95 and the latest version. • 32 MB of RAM.
• 50 MB of hard disk space.
• 10 MB additional RAM for each concurrent CAD session.
1.2 THE LIST OF OTHER CAD PACKAGE
There are many CAD packages that we can use to make a drawing. Each CAD package has an advantage to make drawing easier. Example of the packages are listed below;
• AutoCAD • Catiar • AutoCADLT • MasterCAM • PSPICE • AutoSketch
However, with the advancement of technology, CAD program has undergone changes and updated to meet the need of users.
1.3 ADVANTAGES OF USING AUTOCAD
Although there are many methods used to design and draft activities, CAD offers the following advantages over other methods in many cases:
• Improving productivity, capability and accuracy. • Faster editing, reviewing and designing.
• Save storage for drawing.
1.3.1 Improving productivity, capability and accuracy.
Simple drawing created manually requires lesser time than larger and more complex drawings, particularly those involving similar shapes or repetitive operations. It may take some time to set up the first drawing and create some of the initial geometry, but any of the existing geometry or drawing setup can be easily duplicated in the current or for new drawings.
As CAD and the associated technology advance and software are becoming more interconnected, more productive developments are available. For example, it is possible to make a change to a 3-dimensional model that automatically causes a related change in the linked 2-dimensional engineering drawing. One of the main advantages of these technological advances is productivity.
When you draw with CAD system, the graphical elements, such as lines, arc, and circles are stored in the Cad file as a numeric data. CAD systems store that numeric data with great precision. For example, AutoCAD stores values with fourteen signification digits. The value 1 for example, is stored in scientific notation as the equivalent of 1.0000000000000. This precision provides you with the ability to create design and drawing that are 100% accurate for almost every case.
1.3.2 Faster editing, reviewing and designing.
Making changes to a CAD file known as editing is generally much faster than making changes to a traditional manual drawing. Since all the graphics elements in a CAD drawing are stored, only the affected components of the design or drawing need to be altered, and the drawing can be plotted or printed again or converted to other formats. It can save our time to produce a new drawing.
1.3.3 Improving quality of end product.
The quality of end product is improved because during the development, we use accurate measurement without any confusion.
1.3.4 Save of storage
With conventional method we use drawing paper as a media to save our file. If we have lot of drawing, more space is needed. This storage problem can be solved by using CAD drawing. We just need an electronic storage element such as hard disk or diskette to save a thousand drawing file.
As a student, learning AutoCAD, as opposed to learning another CAD software product, give you a higher probability of using your skills in industry. Likewise, there are employers who use AutoCAD than any other single CAD system. In addition, learning AutoCAD is a first CAD system gives you a good foundation for learning other CAD packages because many concepts and commands introduced by AutoCAD are utilized by other systems. In some cases, an AutoCAD feature becomes industry standards. The .DXF file format, for example, was introduced by AutoDesk and has become an industry standard for CAD file conversion between systems.
ACTIVITY 1a
FILL IN THE BLANK.
1.1 What is the definition of CAD? List its main function.
_________________________________________________________________ _________________________________________________________________ _________________________________________________________________
1.2 List all the CAD packages that you know of.
_________________________________________________________________ _________________________________________________________________ _________________________________________________________________
1.3 List the advantages of using CAD compared to conventional methods. _________________________________________________________________ _________________________________________________________________ _________________________________________________________________ _________________________________________________________________
FEEDBACK TO ACTIVITY 1a
ANSWERS.
1.1 CAD is an acronym for Computer Aided Design or Computer Aided Drafting. CAD allows you to accomplish design and drafting activities using a computer. We can use CAD to draw a building plan, circuit diagram, chart, 3D object and more. (Refer to input 1a page 2 )
1.2 There are many CAD packages that we can use to make a
drawing. Each CAD package has an advantage to make drawing easier. Example of the packages are listed below;
a. AutoCAD b. Catiar c. AutoCADLT d. MasterCAM e. PSPICE f. AutoSketch
1.3. Although there are many methods used to design and draft activities, CAD offers the following advantages over other methods in many cases:
• Improving productivity, capability and accuracy. • Faster editing, reviewing and designing.
• Improving quality of end product. • Save storage for drawing.
INPUT 1b
1.4 STARTING AUTOCAD
In this module, we use AutoCAD R14 package. We can use another AutoCAD version because the basic drawing is similar. Assuming that AutoCAD has been installed and configured properly for your system, you are ready to begin using AutoCAD. To start AutoCAD using any Windows, double click on the icon on the desktop as shown below.
Figure 1.1: AutoCAD R14 Icon
If the icon does not appear on the desktop, press the ‘Start’ button, highlight ‘Programs’, and search for ‘AutoCAD R14’ in the menu. From the list displayed, select ‘AutoCAD R14’.
1.4.1 Start Up Dialog Box
When you start AutoCAD, the ‘Start Up’ dialog box appears. This dialog box includes several tools to help you open an existing drawing or set up a new drawing.
Figure 1.3: Start Up dialog box
The following is the content of the instructions for the ‘Start Up’ dialog box as it explains the purpose of the first four buttons.
The button on the left determine how you begin a drawing
“ Use a Wizard ” - lead through setting up a drawing
“ Use a Template ” - start a drawing based on the template
“ Start from Scratch ”- begin drawing quickly using default English or Metric settings
“ Open a Drawing ” - Open an existing drawing
USE A WIZARD
If you want to set up a drawing using a dialog box, choose ‘Use a Wizard’. You can choose from two wizards: ‘Quick Setup’ and ‘Advanced Setup’.
‘Quick Setup.’
Choose the Quick Setup wizard to set up the drawing area and change settings, such as text height and snap spacing, to an appropriate scale. With the Quick Setup wizard, you establish basic settings that help define the units of measure and drawing area. These settings include the basic unit type (such as architectural, decimal, engineering, fractional, or scientific units) to be used for display and plotting.
You also specify the width and length of the drawing area, and thereby establish the drawing's boundaries, called limits. The area within these limits defines the final plotted sheet size. After you accept the settings, the drawing session will begin.
Step 1: Units
Select the format in which you want to display units of measure. Select the format in which you want to enter and display coordinates and measurements. Several measurement styles are available in AutoCAD. Two of them, Engineering and Architectural, have a specific base unit (inches) assigned to them. You can choose from other measurement styles that can represent any convenient unit of measurement:
Decimal. - Select to display measurements in decimal notation.
Engineering. - Select to display measurements in feet and decimal
inches.
Architectural.- Select to display measurements in feet, inches, and
fractional inches.
Frictional - Select to display measurements in mixed number
(integer and fractional) notation.
Scientific. - Select to display measurements in scientific notation
(numbers expressed in the form of the product of a decimal number between 0 and 10 and a power of 10).
Figure 1.4 : Quick Setup box for step 1.
Step 2: Area
Enter the approximate width and length in full-scale units of what you plan to draw. This limits the area of the drawing covered by grid dots when the grid is turned on. It also adjusts several default settings, such as text height, linetype scaling, and snap distance, to convenient values. You can also adjust these settings, individually, from the Format menu later in the drawing session.
Choose the Advanced Setup wizard to set up the drawing area and change settings, such as text height and snap spacing, to an appropriate scale. You can also establish basic layout features.
Step 1: Units
Select the format in which you want to enter and display coordinates and measurements. Several measurement styles are available in AutoCAD. Two of them, Engineering and Architectural, have a specific base unit assigned to them (inches). You can choose from other measurement styles that can represent any convenient unit of measurement:
Figure 1.6: Advanced Setup box for step 1
The precision that you specify controls the number of decimal places or fractional size to which you want linear measurements displayed.
Step 2: Angles
Select the format in which you want to enter and display angles:
Decimal Degrees. Select to enter and display partial degrees as decimals. Deg/Min/Sec. Select to enter and display partial degrees as minutes
and seconds.
Grads. Select to enter and display angles as grads. Radians. Select to enter and display angles as radians. Surveyor. Select to enter and display angles in surveyor units.
Figure 1.7: Advanced Setup for step 2
Step 3: Angle Measure
Select the direction of the zero angles for the entry of angles:
Figure 1.8: Advanced Setup box for step 3.
East. Select to specify the compass direction east as the zero angle. North. Select to specify the compass direction north as the zero angle. West. Select to specify the compass direction west as the zero angle. South. Select to specify the compass direction south as the zero angle.
as the zero angle.
Step 4: Angle Direction
Select the direction to enter and display positive angle values: counterclockwise or clockwise.
Figure 1.9: Advanced Setup Box for step 4
Step 5: Area
Enter the approximate width and length of what you plan to draw in full-scale units. This limits the area of the drawing covered by grid dots when the grid is turned on. It also adjusts several default settings, such as text height, linetype scaling, and snap distance, to convenient values. You can also adjust these settings, individually, from the Format menu later in the drawing session.
Figure 1.10 : Advanced Setup box for Step 5
Step 6: Title Block
Select the description of an AutoCAD drawing file of a title block to insert as a symbol in your new drawing. You can add or remove drawing files of title blocks from the list with the ‘Add and Remove’ buttons.
Figure 1.11: Advanced Setup box for Step 6
Step 7: Layout
Select Yes to use advanced paper space layout capabilities in AutoCAD. Paper space is often used to create complex multiple-view
space, you have three choices of where you want to begin working.
Figure 1.12: Advanced Setup box for step 7
USE A TEMPLATE.
If you want to start a drawing based on a template drawing, choose Use a Template.
Figure 1.13 : Create New Drawing using Template
Template Drawing is a drawing file that you can use as a starting point for new drawings. It stores all the settings for a drawing and may also include
predefined layers, dimension styles, and views. Template drawings are distinguished from other drawing files by a different file extension, .dwt. They are normally kept in the template directory. Several template drawings are included with AutoCAD. You can make additional template drawings by changing the extensions of drawing file names to have a .dwt extension.
START FROM SCRATCH
If you want to begin drawing quickly using default English or metric settings, choose Start from Scratch.
Figure 1.14 : Create New Drawing box using Start From Scratch
From the Select Default setting field, we can choose either English or Metric setting.
English - Unit measurement is in traditional setting ( Inches )
Metric - Unit measurement is in standard setting ( MM )
1.5 AUTOCAD R14 DRAWING SCREEN
Below are the standard screens for AutoCAD R14. We can adjust the screen weather to add or remove some toolbar or change the toolbar or resize the screen
‘Toolbar’, ‘Layer Status Windows’, ‘Command Line’, ‘Status Line’, ‘Drawing Area’ and ‘Cursor Pointing’.
Menu Bar
Toolbars
Layer Status Window
Crosshair Cursor
Drawing Area
Status Line Command Line
Figure 1.15 : AutoCAD Drawing Screen
Toolbars
AutoCAD R14 provides a variety of toolbars. Each toolbar contains a number of icon buttons that can be selected to invoke command.
Menu Bars
These menus provide an alternative method of accessing command and dialog boxes other than the Command Prompt or a toolbars button. They are termed pull-down menus because when you choose one with your left mouse button, the menu is displayed beneath its title, as if you were pulling the menu down from its title.
Pull-Down Menu
Figure 1.16: Pull-Down Menu
Command Line
The command line is a docked or floating window where you can enter names or command and where AutoCAD displays prompts and messages.
Layer Status Window
Layer status window shows the current layer setting.
Status Line
The status line is a set of informative words or symbols that gives the status of the drawing aids. The following drawing aids can be toggled on or off by double-clicking on the desired word or by using Function keys or Ctrl key sequences.
1.6 GETTING TOOLBARS FROM PULL DOWN MENU
We can use toolbars to perform the desired command like ‘line’, ‘circles’ and other. By default there are four toolbars that appear in the AutoCAD screen. To display another toolbar, we can access the ‘Toolbars’ dialog box in the following ways;
Toolbar : ‘Right clicking any currently visible toolbar’
Menu : View>Toolbar
Figure 1.17: Toolbar Setting Box
Choose any of the toolbar checkboxes displays the toolbar. The toolbar can then be moved anywhere in the application window by selecting the title bar and dragging the toolbar to a location.
1.7 SAVING FILE AND EXIT FROM AUTOCAD
AutoCAD uses different file saving command that protect your work by storing the existing drawing status to a named file in a directory. Saving your work is very important because if there is a power failure, all of your work saved prior to the problem will be usable.
Various file saving commands are used to store drawing information. These command include SAVE, SAVE AS and QSAVE.
The SAVE command saves the drawing with the current filename or a specified name when saved the first time. We can get the command with the following ways
Menu : File>Save
Command : SAVE
The SAVE AS command saves unnamed drawings with a filename, or saves the current drawing with a different name.
The QSAVE command saves currently named drawing one at a time without requesting a filename
Toolbar : Menu : File > Save
Command : QSAVE
Use the following steps to save unnamed drawing
1. Toolbars : ( If we click this button for the first time, the
Save Drawing As box will appear )
Menu : File> Save
Command : SAVE
2. When the Save Drawing As appears, enter the name of the drawing in file name field. ( the file extension is not required)
Figure 1.18: ‘Save Drawing As’ box
After saving the file we can continue or exit the AutoCAD application. To exit from AutoCAD, use the following method;
1. Click at the very right upper button of the screen
Menu : File>Exit Command : EXIT
ACTIVITY 1b
EXERCISES.
1.4 Starting AutoCAD by clicking the ‘AutoCAD R14 shortcut icon’ or ‘AutoCAD R14’ from the ‘programs menu’. If the start up dialog box appears, select ‘start from scratch’. Choose ‘English’ as the default setting, and click the ‘OK’ button. At the AutoCAD screen, name toolbars and menus when we moved the cursor around the screen without clicking.
1.5 Draw a line by typing ‘L’ at the ‘command line’. Click the cursor at the drawing area and move it to other point. Save your drawing and name it ‘exercise1’.
1.6 Exit AutoCAD by selecting the exit option from the ‘pull down menu’ or click the upper right button on the screen. Repeat the open and exit steps until you are confident with the procedure.
1.7 Try to start a new drawing with another set up ‘use a wizard’ and ‘use a template’
1.8 Using the Toolbars Dialog Box
• At the Command prompt enter toolbar. The toolbars dialog box is displayed, as shown in the figure 1.17
• In the Toolbars list box, check the modify 11 checkbox. The Modify 11 toolbar is displayed in the drawing windows as a floating toolbar • Now you will change the Modify 11 toolbar from a floating toolbar to
a docked toolbar. To do this, place the cursor on the title bar on the toolbar, then press and hold the left mouse button
• Drag the modify 11 toolbar to the docking region under the Object Properties toolbar, then release the left mouse button. When the toolbar is docked, the title bar name is no longer displayed.
• In the Toolbar dialog box, clear the Modify 11 Checkbox. The Modify 11 toolbar is no longer displayed.
FEEDBACK
TO ACTIVITY 1b
Once you have completed this activity, please refer to your
lecturer for further comments.
ANSWER ALL THE QUESTIONS BELOW
QUESTION 1-1
a) How many ways can you start an AutoCAD drawing session? What are they?
b) How can you disable and reactivate the display of the Start Up dialog box?
c) Describe the AutoCAD application window and explain each window area. Toolbars Layer Status Wi d Command Line Crosshair Cursor Status Line Menu Bar
d) How many way provided by AutoCAD to begin drawing. Explain.
e) What is the purpose of ‘Advanced Setup’ and list all the steps to draw by using ‘Advanced Setup’ format.
FEEDBACK TO SELF-ASSESSMENT
ANSWERS
QUESTION 1-1
a) Two ways to start AutoCAD
i. Click on icon AutoCAD R14 on the Desktop ii. Press Start>Programs>AutoCAD R14
b) We can activate using the following ways Pull-down menu : File>New
Toolbar :
We can disable by clicking cancel button at start up dialog box and upper right click at the start up dialog box.
c)
Menu Bar
Toolbars
Layer Status Window
Crosshair Cursor
Drawing Area
Status Line Command Line
Toolbars
AutoCAD R14 provides a variety of toolbars. Each toolbar contains a number of icon buttons that can be selected to invoke command.
Menu Bars
These menus provide an alternative method of accessing command and dialog boxes other than the Command Prompt or a toolbars button. They are termed pull-down menus because when you choose one with your left mouse button, the menu is displayed beneath its title, as if you were pulling the menu down from its title.
Command Line
The command line is a docked or floating window where you can enter names or command and where AutoCAD displays prompts and messages.
Layer Status Window
Layer status window shows the current layer setting.
Status Line
The status line is a set of informative words or symbols that gives the status of the drawing aids. The following drawing aids can be toggled on or off by double-clicking on the desired word or by using Function keys or Ctrl key sequences.
d) There are 4 ways to begin the drawing. They are:
“ Use a Wizard ” - lead through setting up a drawing
“ Use a Template ” - start a drawing based on the template
“ Start from Scratch ”- begin drawing quickly using default English or Metric settings
e) ‘Advanced Setup.’
Choose the Advanced Setup wizard to set up the drawing area and change settings, such as text height and snap spacing, to an appropriate scale. You can also establish basic layout features.
Step 1 : Units Step 2 : Angles
Step 3 : Angle Measure Step 4 : Angle Direction Step 5 : Area
Step 6 : Title Block Step 7 : Layout
UNIT 2
ENTERING COMMAND AND
DATA INPUT
OBJECTIVES
General Objective : To understand and use the methods of entering command and data input
Specific Objectives : At the end of the unit you will be able to :
¾ Enter command by three different methods. ¾ Create drawing by coordinate entry.
¾ Use Direct Distance Input to create drawing.
¾ Create a drawing by using Absolute Cartesian Coordinate. ¾ Create a drawing by using Relative Coordinate.
¾ Create a drawing by using Polar Input.
INPUT 2a
2.1 HOW TO BEGIN A COMMAND
There are three possible methods for entering commands in AutoCAD depending on your preferences setting ( for the screen menu ). Generally any one of the three methods can be used to invoke a particular command.
1. Keyboard Type the command name, command alias, or accelerator ( Ctrl ) keys at the keyboard
2. Pull-Down Menu Select the command or dialog box from a pull-down menu.
3. Toolbars Select the command or dialog box by PICKing an icon ( tool ) from a toolbar
2.1.1 Keyboard.
When you enter a command in a command window, AutoCAD either displays a dialog box or prompts you for further information. This line of Command text is termed the Command Prompt. The Command prompt asks you to specify coordinate value, command options, or any other data needed to complete the command. The following text is an example of the Command prompt for the PLINE command.
Figure 2.1 : Example of the Command prompt.
Once you are comfortable entering commands at the Command prompt, you can learn the command aliases, which are basic one- or two- or three- letter abbreviations of the commands. Many commands have an aliases, and learning these can help you work faster and more productively. A list of all the command aliases is located in the Help menu.
2.1.2 Pull Down Menu
When you perform a Typical installation of AutoCad, you are presented with a menu bar containing 10 menus:
Figure 2.2 : Menu Bar with 10 menus.
These menus provide an alternate method of accessing command and dialog boxes other than the command prompt or toolbar button. They are term pull down menu because when you choose one with your left mouse button, the menu is display beneath its title, as if you were pulling the menu down from its title. The menu remains present until you click anyway outside of it.
2.1.3 Toolbars
Another method of performing commands is through the various toolbar tools. There are many tools in the 21 toolbars, but those most frequently used, relating to file, edit and view, are found in the Standard toolbar, shown in the following figure:
Figure 2.3 : Standard Toolbars
To display other toolbars, you can access the Toolbar dialog box in the following ways:
Toolbar : Right click any currently visible toolbar Menu : View > Toolbars
Command : TOOLBAR
The Toolbars dialog box is displayed as shown in figure below:
Figure 2.4 : Toolbars dialog box
Clik on the box to choose any toolbars you need to use. Then, clik ‘Close’ button to end the session.
ACTIVITY 2a
FILL IN THE BLANK.
2.1 List three methods for entering command in AutoCAD R14. Explain. i.
ii. iii.
2.2 Give the steps to access the ‘line’ command to draw a line by using the pull down menu.
2.3 How can we display the ‘toolbar box?
Feedback To Activity 2a
ANSWERS.
2.1.
1. Keyboard Type the command name, command alias, or accelerator ( Ctrl ) keys at the keyboard
2. Pull-Down Menu Select the command or dialog box from a pull-down menu.
3. Toolbars Select the command or dialog box by PICKing an icon ( tool ) from a toolbar
2.2. Pull Down Menu : Draw > Line
2.3. Toolbar : Right click any currently visible toolbar Menu : View > Toolbars
INPUT 2b
2.2 CREATING DRAWING BY USING COORDINATE ENTRY
AutoCAD provides various commands that you use to locate points in the drawing plane. You can create a drawing by using Direct Distance entry, Absolute Coordinates, Relative Coordinates, and Polar entry methods.
2.2.1 Direct Distance Entry.
To enter point you can use a feature called direct distance entry. With direct distance entry, you can specify a relative coordinate by moving the cursor in the desired direction and then entering a distance.
Coordinate value are specified by moving the cursor to indicate a direction and then entering the distance from the first point. This is useful when you need to quickly specify a length. An efficient way to create object constrained to the current axes is to use direct distance entry combined with Ortho mode turned on.
Direct distance entry can used with all commands except those that prompt you to enter real values. This commands include ARRAY, MEASURE, and DIVIDE.
2.2.2 Absolute Cartesian Coordinate Input.
Absolute coordinate system can be used when you know the exact X and Y values of the point you want to place in the drawing window. The absolute coordinates method uses the Cartesian coordinate system to locate points in the drawing window. All points are measure from origin (0,0).
The Cartesian coordinate system has three axes X, Y, and Z that are used to locate points and create objects. The Cartesian coordinate system uses distances ( in unit ) to locate points along intersecting axes, the horizontal ‘X’ axes and the vertical ‘Y’ axes. The intersection of these axes called the origin, where X = 0 and Y = 0 denoted as ( 0,0). These axes divide the coordinate system into four quadrant each having positive, negative or positive and negative X and Y values.
You can draw a line by starting at the 0,0 and end at the point 3,4
Figure 2.5 : Two dimensional Cartesian coordinate system.
World Coordinate System ( WCS )
When start a new session, by default you enter the World Coordinate System (WCS). This system consist of a horizontal X displacement, a vertical Y displacement, and a Z displacement that is perpendicular to the XY plane. The Z displacement is used for 3D drawing. All X,Y and Z coordinate values are measured from the origin. The origin is located at the intersection of X, and Y axes (0,0). The origin is originally located in the lower left corner of a drawing. The WCS cannot be redefined, and all other user coordinate system are based on the WCS.
User Coordinate System ( UCS )
The User Coordinate System ( UCS ) lets you establish your own coordinate origin. The UCS is movable, meaning that the origin can be moved to any desired orientation and its axes can be rotated. The UCS icon is displayed by default in the lower left corner of the drawing window. The icon is used to help better understanding the location and orientation of the movable UCS. The X and Y arrows point in the positive direction of the axis. The W in the following figure indicates the WCS is current. The UCS icon is shown in the following figure:
Figure 2.6 : UCS icon
Method for invoking the UCS command include: Toolbar : Standard
Menu : Tools > UCS Command : UCS
Relative Cartesian Coordinate Input.
A relative Cartesian coordinate is entered as the X and Y distance from the last point you specified. Use relative X,Y coordinate when you know the position of a point in relation to the previous point. For example, to locate a point at a relative direction of 4,5 from the first point specified, precede the next coordinate with the @ symbol. The following example demonstrate how to enter a relative coordinate:
At the command prompt, enter line.
In response to the From point command prompt, enter 0,0 In response to the To point command prompt, enter @4,5.
Figure 2.7 : example to entering relative coordinate
Polar Input
A polar coordinate is entered as a relative distance and angle from an absolute coordinate or the last point specified.
To enter a polar coordinate, enter a distance and an angle, separated by an angle bracket (<). For example to specify a point that is at a distance of 2.5 units from the previous point and an angle of 45 degree, enter @ 2.5 < 45.
By default, angles increase in the counterclockwise direction and decrease in the clockwise direction. To move clockwise, enter a negative value for the angle. For example, entering @3<-45 is the same as entering @3<315.
Figure 2.8 : Polar coordinate angles
ACTIVITY 2a
ANSWER ALL THE QUESTIONS BELOW.
2.4
figure 3.7
a) Refer to the figure 3.7, determine
1) the polar coordinate of Point “E” from Point “D” 2) the absolute coordinate of the center of circle “I” 3) the polar coordinate of Point “A” from Point “H”
b. Supply the appropriate absolute, relative and/or Polar coordinates for these `figure in the matrix below each object.
5 4 3 6 7 2 15 11 14 10 13 12 9 8 1/17 16
FEEDBACK TO ACTIVITY 2b
ANSWERS 2.4 a) 1. @4 < 90° 2. 6,10 3. @12 < 270° / @12 < -90° b) @ 0, 5.0 @5 <90 @ 2<0 0.5,5.0 2.5 , 5.0 @ 2.0, 0 2.5 , 7.0 @ 0, 2.0 @ 2 < 90 @ 7 < 0 9.5 , 7.0 @ 7.0 , 0 9.5 , 5.0 @ 0 , -2.0 @ 2.0 , 0 @ 2 < 270 @ 2 < 0 11.5 , 5.0 @ 5 < 270 11.5 , 0.5 10.0 , 0.5 @ 0 , -5.0 @ -1.5 , 0 @ 1.5 < 180 10.0 , 3.5 @ 0 , 3.5 @ -3.3 , 0 @ 0 , -1.0 @ 3.5 < 90 6.8 , 3.5 @ 1 < -90 @ 3.3 < 180 6.8 , 2.5 5.0 , 2.5 @ -1.5 , 0 @ 0 , 1.0 @ 1.5 < 180 @ 1 < 90 5.0 , 3.5 @ -3.3 , 0 @ 3.3 < 180 2.0 , 0.5 0.5 , 0.5 2.0 , 3.5 @ 0 , 3.5 @ 3.5 < 270 @ -1.5 , 0 @ 1.5 < 180SELF- ASSESSMENT
ANSWER ALL THE QUESTIONS BELOW
QUESTION 2-1
a) List all the way to create the drawing by coordinate entry.
b) Explain the methods to entering command.
QUESTION 2-2
a) Construct one-view drawings of the following figure using the LINE command along with coordinate or direct distance modes.
b) Complete the table below with Absolute and Relative Coordinate according to figure below.
FEEDBACK TO SELF-ASSESSMENT
ANSWERS.
QUESTION 2-1.
a) CREATING DRAWING BY USING COORDINATE ENTRY
AutoCAD provides various commands that you use to locate points in the drawing plane. You can create a drawing by using Direct Distance entry, Absolute Coordinates, Relative Coordinates, and Polar entry methods.
b) There are three possible methods for entering commands in AutoCAD depending on your preferences setting ( for the screen menu ). Generally any one of the three methods can be used to invoke a particular command.
1. Keyboard Type the command name, command alias, or accelerator ( Ctrl ) keys at the keyboard
2. Pull-Down Menu Select the command or dialog box from a pull-down menu.
3. Toolbars Select the command or dialog box by PICKing an icon ( tool ) from a toolbar
2-2 b) 3.65 , 3.25 @ 2.5 , 0 5.5 , 3.0 @ -1 , -1 2.0 , 2.0 @ 0 , -1 4.5 , 0 3.65 , 3.25 @ 0 , 0.5 @ 2.0 , 0 @ 1 , -0.5 4.5 , 4.5 5.5 , 4.0 2.5 , 4.50 @ 0.5 , 0 2.5 , 3.75 @ 0 , 1.75 2.0 , 3.75
DRAWING AIDS,
DRAWING LIMITS AND DISPLAY CONTROL
UNIT 3
OBJECTIVES
General Objective :To understand and apply the concept of drawing aids, drawing
limits and display control
Specific Objectives : At the end of the unit you will be able to :
¾ Specify the Snap and Grid increment.
¾ Use the Setup and Create New Drawing dialog boxes to accomplish basic drawing setup.
¾ Use the various OSNAP command options. ¾ Use the various ZOOM command options.
¾ Adjust the display using Realtime ZOOM and PAN modes.
¾ Use the Ariel View feature to Zoom and Pan different parts of a drawing.
¾ Create and restore views with the View Control dialog box.
¾ Use and distinguish the REDRAW, REGEN, and REDRAWALL commands.
INPUT 3a
DRAWING AIDS
3.0 INTRODUCTIONWhen placing a line, arc or circle in a drawing, the easiest method is to enter point by selecting a point in the drawing windows. The problem with these methods is that it is inaccurate. To assist you in selecting points in the drawing windows, you can setup the drawing aids to suit the design requirements of your current project.
AutoCAD provides with a number of features that will increase your efficiency and make more productive. Many of these features are contained in the Drawing Aids dialog box. They include Snap, Grid and Ortho as shown in the Figure 3.1
Figure 3.1 : Drawing Aids Dialog Box
Methods for opening the Drawing Aids dialog box include:
Menu : Tools> Drawing Aids Command : DDRMODES
The Ortho option is used to turn Ortho mode ON or OFF. By selecting Ortho command, we can draw a line weather horizontal or vertically.
The Solid Fill mode option controls whether objects such as Polylines with widths and Solids are displayed filled or in outline. This mode can be controlled from the command line using the FILL command.
When Quick Text is checked, all text objects in the drawing will be displayed with empty boundary boxes. This option is often used to increase Regen and Redraw times when the drawing has a lot of text. This mode can also be set using the QTEXT command.
The Blips option controls whether temporary blips will be displayed when points are picked or entered. Blips can be removed from the display using the Redraw command but they can only be suppressed completely by turning Blip mode OFF. This mode can also be set using the BLIPMODE system variable.
Highlight mode determines whether objects are highlighted or not when they are selected.
You can also control highlighting using the HIGHLIGHT system variable.
The Groups option turns automatic Group selection ON and OFF. When Groups mode is turned ON, selecting an object which is a member of a previously defined group will automatically select the whole group.
The Hatch option determines whether the hatch boundary is selected when a hatch object is selected or not. When this mode is turned ON, the boundary is automatically selected with the hatch.
3.1 SNAP
SNAP, when activated by pressing F9 or double-clicking on SNAP in the status line (
Figure 3.2 ) forces the cursor position to regular increments. The function can be assistance
to you by making it faster and more accurate for creating and editing objects. The default
snap setting is 0.5 The Snap command is used to set the value for these invisible snap
Figure 3.2 : The Status Line
The Snap command is easily typed, displaying the options in command line format. The command line format is as follows:
Command : Snap
Snap spacing or ON/OFF/Aspect/rotate/Style< current value ): ( value or letter ) ( enter a value or option )
ON/OFF
Selecting ON or OFF accomplishes the same action as toggling the F9 key, pressing
Ctrl+B, or double clicking SNAP on the status line. Typically, SNAP should be ON for
drawing and editing but turned OFF to make object selection easier ( the cursor moves smoothly to any location with SNAP OFF )
Aspect
The Aspect option allows specification of unequal X and Y spacing for SNAP. This action can also be accomplished in the drawing Aids dialog box by entering different values for X
Spacing and Y Spacing.
Rotate
SNAP can also be rotated about any point and set to any angle. When SNAP has been rotated, the GRID, ORTHO, and “crosshairs” automatically follow this alignment.
Style
The style option allows switching between a standard snap pattern ( the default square or rectangular ) and an Isometric snap pattern. If using the dialog box, toggle Isometric Snap/Grid On. When the SNAP Style or Rotate angle is changed, the GRID automatically aligns with it.
GRID is visible on the screen, whereas SNAP is invisible. GRID is only a visible display of some regular interval. GRID and SNAP can be independent of each other. In other words, each can have separate spacing settings and the active state of each (ON, OFF) can be controlled independently. The GRID follows the SNAP if SNAP is rotated or changed to Isometric Style. Although the GRID spacing can be difference than SNAP, it can also be forced to follow SNAP by using snap option. The default GRID setting is 0.5.
Figure 3.3 : The GRID is ON in the drawing area
The GRID cannot be plotted. It is not comprised of point object and therefore is not part of the current drawing. GRID is only visual aids.
Grid can be accessed by command line format ( shown below ) or set via the Drawing Aids dialog box ( Figure 3.2 ).
Command : grid
Gridspacing ( X ) or ON/OFF/Snap/Aspect<current value>: (value or letter) ( enter a value or option )
Grid spacing ( X )
If you supply a value for the grid spacing, GRID is displayed at the spacing regardless of SNAP spacing. If you key in an X as a suffix to the value ( for example, 2X ), the GRID is displayed as that value times the SNAP spacing ( for example, “2 times” SNAP )
ON/OFF
The ON and OFF options simply make the grid visible or not ( like toggling the F7 key, pressing Ctrl+G or double clicking GRID on the status line.
Snap
The snap option of the grid command forces the GRID spacing to equal that of SNAP, even if SNAP is subsequently changed.
Aspect
The aspect option of Grid allows difference X and Y spacing ( causing a rectangular rather than a square GRID )
3.3 THE FUNCTION KEYS
Many of the modes described above can be controlled quickly using the keyboard function keys. In most cases this is quicker than using a pull-down or the command line. The function keys are arranged along the top of your keyboard. AutoCAD uses function keys F1 to F10. Their use is described below.
The F1 key on your keyboard brings up the "Help Topics: AutoCAD Help" dialogue box. You can use this dialogue box to search for help on any AutoCAD command or topic. Simply follow the instructions in the dialogue box and when you have found the item you wish to view, click on the "Display" button. You will usually be given a list of options in the "Topics Found" dialogue box, select the most appropriate and click the "Display" button to see the item.
Figure 3.4: Help Topic Box
The F2 key is used to toggle (turn ON and OFF) the AutoCAD text window. This is a floating version of the command window which can be resized to suit your requirements. The text window contains the whole command history from the beginning of the drawing session. If you wish, you can scroll back to see which commands you have used. The text window is also useful for viewing the results of commands like ‘LIST’ which report to the command line on a number of lines which may scroll off the command window and make them difficult to view.
Figure 3.5: AutoCAD Text Windows
The F3 key displays the "Osnap Settings" dialogue box.
The F4 key on your keyboard toggles tablet mode ON and OFF. This only has an effect if a digitizing tablet has been calibrated.
The F5 key cycles through the Isoplanes, this only has an effect if "Isometric Snap/Grid" mode is ON. The options are Left, Top and Right. The different options describe the plane in which Ortho mode works. It also affects the orientation of Isocircles drawn with the Ellipse command. The illustration on Figure 3.6 shows a cube with ‘isocircles’ drawn on the top, left and right faces. Each isocircle was drawn using the corresponding isoplane.
Figure 3.6
The F6 key is a three way toggle which changes the co-ordinate reading in the status bar. By default the status bar shows co-ordinates using the Cartesian system. You can use the F6 key to turn the co-ordinate readout OFF and to change to the polar system when you are in pick mode.
The F7 key is used to toggle grid mode ON and OFF. When grid mode is ON a grid of dots is shown on the screen as a drawing aid. You can set the grid spacing by using "Drawing Aids" from the "Tools" pull-down. The grid points do not necessarily reflect the Snap setting, they can be set independently, and however, you can force the grid to reflect the snap setting by giving the grid setting a value of zero. The word "GRID" is highlighted in the status bar when grid is set ON.
When Ortho mode is ON AutoCAD will only allow you to draw either vertical or horizontal lines. You can think of it as being a computer version of the parallel motion on your drawing board. You can see if Ortho mode is ON by looking at the status bar. The word "ORTHO" is highlighted when Ortho is turned ON.
The F9 key can be used to toggle Snap mode ON and OFF. Snap makes the crosshairs jump to points on a defined grid. The snap spacing can be set using the "Drawing Aids" dialogue box from the "Tools" pull-down menu. You can also see if Snap mode is ON by looking at the status bar.
The F10 key is used to control the display of the status bar, the display can be toggled OFF and ON.
3.4 OBJECT SNAP
The Object Snaps (Osnaps for short) are drawing aids which are used in conjunction with other commands to help you draw accurately. Osnaps allow you to snap onto a specific object location when you are picking a point. For example, using Osnaps you can accurately pick the end point of a line or the center of a circle. Osnaps in AutoCAD are so important that you cannot draw accurately without them. For this reason, you must develop a good understanding of what the Osnaps are and how they work.
This simple example is to give you an idea how Osnaps work. Follow the command sequence below to draw a circle and then to draw a line from the center point of the circle to a point on the circle's circumference at the 12 o'clock position.
To Draw the Circle
Command: CIRCLE
3P/2P/TTR/<Center point>:
(pick a point in the middle of the drawing window) Diameter/<Radius>:
(pick another point to draw the circle, the size is not important)
To Draw the Line using Osnaps
Command: LINE
From point: CEN (this is the short-cut for the Center Osnap)
_cen of (pick a point on the circumference of the circle, P1 in the illustration) To point: QUA (this is the short-cut for the Quadrant Osnap)
_qua of (pick a point on the circumference of the circle, P2 in the illustration)
To point: (to end)
When you use Osnaps you need only pick a point which is near to the point required because AutoCAD automatically snaps to the object location implied by the particular Osnap you use. Notice that when you move the cursor close enough to an Osnap location, it is highlighted with an Osnap marker. Each Osnap has a different marker. As you have already seen, the Center Osnap marker is a circle and the Quadrant Osnap marker is a diamond. Notice also that when you move the cursor over a snap point the cursor jumps to the snap location. This feature is known as Magnet.
One thing that often catches new users out is that when you want to snap to the centre of a circle, the pick point should be on the circle's circumference. This is because the circle has no solidity, it is only an outline.
Although you can get quite close to the result above by picking freehand you will never be able to pick as accurately as you can using Osnaps. Many AutoCAD
commands rely upon the fact that objects have been drawn accurately and so you should always use Osnaps when you need to pick a point at a particular location.
There are four basic methods of accessing the Osnaps:
• The Osnaps are available from a flyout button on the Standard toolbar, see illustration on Figure 3.8
already displayed, you can display it using the TOOLBAR command, View
Toolbars… from the pull-down menu. When the Toolbar dialogue box appears,
simply check the box next to "Object Snap" in the toolbars list. Many AutoCAD users work with the Object Snap toolbar permanently docked on their screen because it gives one-click access to all of the Osnaps, making drawing much more efficient.
• You can also access the Osnaps from the cursor menu. Hold the Shift key down on the keyboard and right-click the mouse to bring up the cursor menu. The menu appears at the current cursor position.
• Finally, you can also access the Osnaps from the keyboard by typing their abbreviated name.
There are eleven Osnaps in all and although they are all useful in certain situations you will probably find yourself using about half of them on a regular basis and the other half in special circumstances. However, it's a good idea to get to know all of the Osnaps so that you can plan your drawing, knowing all of the tools at your disposal. A sensible use of Osnaps is the best way to improve your drawing efficiency.
Each of the sections below is accompanied by a small screen-shot illustrating the Osnap in use. In each case, drawing objects are shown in pale blue (cyan), the Osnap marker is shown in red and the cursor cross-hairs in white. The corresponding Snap Tip is also shown. Snap tips appear if you let the cursor hover over an Osnap location for a second or so and have a similar function to the toolbar Tool Tips.
Endpoint
Toolbar :
Pull-down : Shift + Right Click Endpoint Keyboard : END (when selecting objects)
The Endpoint Osnap snaps to the end points of lines and arcs and to polyline vertices. This is one of the most useful and commonly used Osnaps.
Midpoint
Toolbar :
Pull-down : Shift + Right Click Midpoint Keyboard : MID (when picking)
The Midpoint Osnap snaps to the mid poins of lines and arcs and to the mid point of polyline segments.
Intersection
Toolbar :
Pull-down : Shift + Right Click Intersection Keyboard : INT (when picking)
The Intersection Osnap snaps to the physical intersection of any two drawing objects (i.e. where lines, arcs or circles etc. cross each other) and to Polyline vertices. However, this osnap can also be used to snap to intersection points which do not physically exist. This feature is called the Extended Intersection (see the illustration above). To use the apparent intersection feature, you must pick two points to indicate which two objects should be used.
Apparent Intersect
Toolbar :
Pull-down : Shift + Right Click Apparent Intersect Keyboard : APP or APPINT (when picking)
two lines may not physically intersect. One line may be at ground level and the other may be 10 meters or more above or below ground level. As with the Intersection Osnap, Apparent Intersection also has an "Extended" mode.
Center
Toolbar :
Pull-down : Shift + Right Click Center Keyboard : CEN (when picking)
The Center Osnap snaps to the centre of a circle, however, the pick point used to pick the centre must be on the circumference of the circle. This often causes some confusion for new users.
Quadrant
Toolbar :
Pull-down : Shift + Right Click Quadrant Keyboard : QUA or QUAD (when picking)
The Quadrant Osnap snaps to one of the four circle quadrant points located at north, south, east and west or 90, 270, 0 and 180 degrees respectively.
Tangent
Toolbar :
Pull-down : Shift + Right Click Tangent Keyboard : TAN (when picking)
The Tangent Osnap snaps to a tangent point on a circle. This osnap works in two ways. You can either draw a line from a point to the tangent point (see illustration) or you can draw a line from a tangent point, the latter is reffered to as the "Deffered Tangent" snap mode.
Perpendicular
Toolbar :
Pull-down : Shift + Right Click Perpendicular Keyboard : PER or PERP (when picking)
The Perpendicular Osnap snaps to a point which forms a perpendicular with the selected object. As with the Tangent Osnap, Perpendicular can be used to draw a line to a perpendicular point, as in the illustration or from a perpendicular point, known as the "Deffered Perpendicular" snap mode
Insert
Toolbar :
Pull-down : Shift + Right Click Insert Keyboard : INS (when picking)
The Insert Osnap snaps to the insertion point of a block, text or an image.
Node
Toolbar :
Pull-down : Shift + Right Click Node Keyboard : NODE (when picking)
The Node Osnap snaps to the center of a Point object. This osnap can be useful if you have created a number of Points with the ‘Measure’ or ‘Divide’ commands. You could, for example insert a number of regularly spaced tree symbols (blocks) along a line by using the
Figure 3.9
The image above shows a Spline (cyan). The Measure command has been used to set Points (red) at regular intervals and a tree symbol has been inserted with the Insert command at each Point location using the Node Osnap.
Nearest
Toolbar :
Pull-down : Shift + Right Click Nearest Keyboard : NEA or NEAR (when picking)
The Nearest Osnap snaps to the nearest point on a drawing object. This Osnap is useful if you want to make sure that a pick point lies on a drawing object but you don't necessarily mind exactly where it is located.
From
The From Object Snap is a little more complicated than the other object snaps but it is well worth getting to know because it can be very useful.
Toolbars :
Pull Down : Shift + Right Click From Keyboard : FROM ( When Picking )
The From Osnap can be used in conjunction with other osnaps or ordinary pick points and
relative co-ordinates to pick offset points. The From Osnap does not snap to object snap
locations, rather it can be used to snap to points at some distance or offset from an object snap location. Consider the following example.
Look at the illustration on the right. It shows a circle drawn on top of a line. It is quite difficult to see how this circle could have been drawn accurately without the use of construction lines. However, the From Osnap can be used to draw the circle without any construction lines. Follow the command sequence below to discover how this is done.
To draw the Line Command: LINE
From point: (pick a point in the lower half of the screen) To point: @0,30
(this is a relative co-ordinate, 30 units above the first point) To point: (to end)
To draw the Circle Command: CIRCLE
3P/2P/TTR/<Center point>: FROM
_from Base point: END ( click at the top of line ) _endp of <Offset>: @0,10
(this co-ordinate is a point 10 units from the endpoint in the Y direction)Diameter/<Radius> <10.0000>: 10
(a radius value of 10 ensures that the southern point on the circle will just touch the top of the line)
Your drawing should now look like the illustration above. Practice using the From Osnap until you are quite sure how it works. Don't forget to prefix all co-ordinates with the @ symbol to let AutoCAD know that you are entering a relative co-ordinate. The North Point
3.5 DRAWING LIMITS
The limits command allows you to set the size of the drawing area by specifying the lower left and upper right corners in X,Y coordinates values. Methods for invoking the limits command include :
Pull-down menu : Format>Drawing Limits Command : Limits
When using command line, we can get the following step
Command : limits
Reset Model space limits
ON/OFF/<Lower left corner><0,0 or current values>: x,y or Enter ( Enter an X,Y value or accept the 0,0 default-normally use 0,0 as lower left corner. )
Upper right corner < 19,9>:x,y ( Enter new values to change upper-right corner to allow adequate drawing area.)
The default Limits values in AutoCAD are 12 and 9; that is, 12 units in the X direction and 9 unit in the Y direction ( figure 3.10 ). Starting a drawing by any of the following methods ( of the setup or create new Drawing dialog boxes ) results in limits of 12 X 9
