Autocad Tutorial

An Introduction to AutoCAD 2D and 3D

Dr. Satish Annigeri Professor of Civil Engineering

Civil Engineering Department

B.V. Bhoomaraddi College of Engineering & Technology Hubli 580 031

6-7 October, 2007

AutoCAD Getting Started You can start AutoCAD in one of the following ways: 1. Double click the AutoCAD icon on the desktop. 2. From the Start menu

When AutoCAD starts up, you are presented with a dialog box shown below:

If this dialog box does not appear, select Tools Options System and select Show startup dialog checkbox. The dialog box will be displayed the next time AutoCAD is started. So, shut down AutoCAD and restart it. To shut down AutoCAD select File Exit or press the Close icon on the top right corner of the AutoCAD window. The options available in this dialog box are: (i) Open an existing drawing (ii) Start a new drawing from scratch (iii) Start a new drawing based on a previously defined template or (iv) Start a new drawing under the guidance of a wizard. To start a new drawing. a beginner is advised to use the wizard. An experienced user can choose either the “start from scratch” or “Use a template” options.

The AutoCAD User Interface The AutoCAD user interface consists of the following components: 1. Main Menu: Contains the menu items File, Edit, View, Insert, Format, Tools, Draw, Dimension, Modify, Window, and Help. They can be accessed using the mouse or the keyboard (Alt+hotkey). 2. Toolbars: Toolbars can be turned on or off. Usually the following toolbars are turned on – Standard, Object properties, Draw and Modify. Toolbars can be turned on/off in one of two ways: a. View Toolbars… b. Right click on any toolbar and select the toolbar to be turned on/off. 3. Drawing Area: Can be either (i) Model space or (ii) Layout (Paper space), depending on the tab selected. You can create multiple layouts (paper space) but there can be only one model space. Model space permits creation and modification of the model. Layout shows how the model appears when plotted on paper of a chosen size. 4. Command window: Command window is located at the bottom and echoes all commands entered through the keyboard or equivalent command for menu selections. 5. Status Bar: Displays the coordinate of the mouse pointer and the status of various switches, such as Coordinates of mouse location, Snap, Grid, Ortho, Polar, Object Snap, Object Snap Tracking, Show/Hide Line weight, Model/Paper space. Any operation in AutoCAD can be initiated in one of two ways: (i) Choosing the appropriate item from the menu (ii) Typing a command into the command window. A command is terminated by pressing <Enter> key or the space bar. Commands are case insensitive. Any command can be terminated midway by pressing the <Esc> key.

Online Help System The user interface offers help in many ways. Some of these are: 1. Tool tips: Pausing the mouse over an icon on any toolbar or status bar displays a short name for the icon. 2. F1 key: Pressing the F1 key displays context sensitive. Thus, pressing F1 when the Tools menu is open shows help specific to this menu item. If no menu items are open, the online help book is opened. 3. To get explanation about any item in a dialog box, click the Question Mark icon at the top right of the window and click on the item to be explained. A brief explanation is offered about the item in the form of a small note. 4. Online help book: This is activated through the Help AutoCAD Help menu item.

Initial Settings of a new Drawing Setting Units When a new drawing is started, it is good practice to set the following parameters, or check them if they are already set using the wizard: Units (Format Units or Command: units) and Limits (Command: limits). The Units command sets the units to be used for lengths and angles, their precision and the direction in which angles are to be measured. Following options are available for lengths: Unit System Architectural

Units used

Method of entering fractional units

Inch and Feet

Fractional

Any

Decimal

Inch and Feet

Decimal

Fractional

Any

Fractional

Scientific

Any

Decimal

Decimal Engineering

Where inch and feet units are used, a double quote (“) indicates inch and an apostrophe („) indicates foot. It is assumed that 12 inches make a foot. Where units are indicated as “any”, the user can use any units, but the responsibility of subdividing each unit into sub units rests with the user. Setting Limits Limits define the extent of a drawing. It is defined in terms of the coordinates of the bottom left and top right corners of the area enclosing the drawing. It can be altered at any time, and is used to determine the area to be shown corresponding to a Zoom All command. Usually one of the coordinates of the top right corner will be altered to maintain the aspect ratio of the drawing area. The first commands when setting up a new drawing are: 1. Units 2. Limits 3. Zoom All For the purpose of this tutorial, let us choose the following: Units: Decimal and let us use metre units with a precision of 4 decimal places. Let the limits be (0,0) to ((120, 90) metres. Then choose Zoom All from the keyboard. Move the mouse to the bottom left and top right corners and read out the coordinates to confirm that the settings have taken effect.

Drawing Some Simple Objects Let us draw a few objects before proceeding. Let us draw a line with end coordinates (5, 2.5) and (10, 5), a circle with its centre at the second point of the previously drawn line and a radius of 2. Then draw a rectangle of width 5, 2 with the lower left corner located at (5, 6). Zoom if necessary to work comfortably. The drawing at this moment must appear similar to what is show below:

Specifying Coordinates Coordinates for a point can be specified in either (i) rectangular coordinates (x, y, z). When only two coordinates are given, they are assumed to be (x, y) or (ii) polar coordinates (r, ). For either coordinate system, coordinates of a point can be specified in absolute or relative coordinates. Absolute rectangular coordinates are specified as x, y, z or x, y with reference to the origin of the coordinate system. Relative coordinates are specified as @x, y, z or @x, y. If a reference point is not specified, the previous drawn point is taken as the reference. To use a previously drawn point as the reference, use the “from” keyword and use OSNAP to choose the point. Absolute Polar coordinates are specified as r

Zoom and Pan Command: Z or Zoom. Menu: View  Zoom. Command: P or Pan. Menu: View  Pan.

θ

. And relative Polar coordinates as @r

θ.

Zoom and Pan help you to work comfortably within the model space. “Zoom in” magnifies the details of the model and “Zoom out” reduces the details. Pan helps you to view a different part of the model within the drawing area. The command for Zoom is Z. Zoom All shown the entire limits of the drawing within the drawing window. “Zoom Center” allows you to choose a point and a magnification and the chosen point is put at the centre of the drawing area while at the same time, drawing is magnified by the specified amount. Magnification can be specified as 2x to magnify the view by 2 times. To zoom out, use a magnification scale less than one, for example 0.5x to reduce the view to half the current size. Zoom Window allows you to choose the diagonal points of the area you wish to view. The command for Pan is P which turns the cross hair cursor into a hand cursor. You can then click and drag with the mouse to pan the drawing. Zoom and Pan affect only the view not the size and dimension of the model.

Object Snap and Object Snap Tracking It is possible to use previously drawn points as reference points or starting points to carry out other drawing operations. The following points can be snapped with the mouse: Endpoint End Extension Ext Mid point Mid Tangent Tan Center Cen Intersection Int Node Node Quadrant Qua To activate OSNAP, click on OSNAP on the status bar so that it is depressed. To choose which type of OSNAP to use dynamically, right click on OSNAP on the status bar and click on Settings. In the dialog box, click on the types of OSNAP you wish to use dynamically. Now moving the mouse near to one of the types of pints displays a yellow coloured symbol to assist in OSNAP. OTRACK assists in aligning drawing operations with existing points. To activate OTRACK, click on OTRACK on the status bar so that it is depressed. To choose which type of OTRACK to use dynamically, right click on OTRACK on the status bar and click on Settings. In the dialog box, click on the types of OTRACK you wish to use dynamically. Now moving the mouse near to one of the types of points displays a dotted line and a cross mark to assist in OTRACK.

Object Properties Window The attributes or properties of an object can be inspected using the properties window. To activate the Object Inspector window, select an object, right clock on the selected object and click on Properties. It is possible to change the properties in the property window and the changes will be effected immediately. When multiple objects are selected, only those properties that are common to the selected objects can be changed.

Drawing Objects Drawing Lines Command: L or Line. Menu: Draw Line. Look at the command window and you will see the prompt “LINE Specify first point:”. At this point key in the coordinates 5,2.5 <Enter>. Immediately the starting point of the line is fixed and a line is drawn up to the current position of the mouse. If the mouse is moved, the line follows the movements. At the same time the command window shows the prompt “Specify next point or [Undo]:”. You can either supply the coordinates of the second point or undo the previous action and start over again. To undo, enter U<Enter> from the keyboard. Otherwise key in the coordinates of the second point as 10,5<Enter>. Drawing Poly Lines Command: PL or PLine. Menu: Draw Polyline. A polyline is similar to a line except that a series of segments of a line are treated as separate entities while a series of segments of a polyline are treated as a single entity. A PLINE can be exploded into a number of line segments. A series of contiguous line segments can be converted into a PLINE with the PEDIT command. Drawing Circles Command: C or Circle. Menu: Draw Circle Center, Radius. The command prompt says “CIRCLE Specify centre point for circle or [3P/2P/Ttr (tan tan radius)]:”. Take the mouse pointer to the second point of the previously drawn line and you will see a small yellow rectangle appear and

a little later the tooltip “Endpoint” appears. If the rectangle does not appear, check the Status Bar to ensure that OSNAP is pressed. Then click the left mouse button to specify the center of the circle. You have made use of Object Snapping. Immediately the center of the circle is fixed and a circle with radius specified by the mouse position is drawn, and movement of the mouse causes the circle to change in radius. The command prompt at this time says “Specify radius of circle or [Diameter]:”. Key in 2<Enter>. Drawing Rectangles Command: Rectang. Menu: Draw Rectangle. To draw a rectangle, specify the points on the diagonal of the rectangle. Sides of the rectangle are drawn parallel to the x-y axes.

Modifying Objects Erasing an Object Command: E or Erase. Menu: Modify  Erase. To erase objects, you must first select the objects to be erased. The cross hair cursor changes to a square box during the object selection process. Selection of a group of objects prior to or during some Modify operations, such as, copy, erase, move, scale can be done in one of the following ways: a. Use a left–to–right window to select completely enclose the objects b. Use a right–to–left window to select all enclosed and crossing objects c. Click on an object to add it to the selection d. Type “all” in the command window to select all objects e. Type “p” to select the previously selected group of objects f. Type “l” to select the last drawn object. Deselecting selected objects during a select operation can be done in a similar way but first pressing “r” on the keyboard to indicate that the objects are to be removed from the selection. Selection process can be resumed by pressing “a” to indicate that objects are to be added to the selection. The selected items are shown in dotted lines. Once the objects to be erased are selected pressing <Enter> or <Space> will erase the objects. Offsetting an Object Command: O or Offset. Menu: Modify Offset. Any drawn object can be offset through a specified distance in the specified direction. It is possible to offset any object, not just lines. Offsetting a line results in a double line. Offsetting a circle results in concentric circles. Trimming Objects Command: TR or Trim. Menu: Modify  Trim. To trim an object, you must first choose one or more cutting edges. Cursor changes to a square during the cutting edge selection process. Press <Enter> or <Space> to indicate end of selection of cutting edges. The cursor is still a square. Now click on the portion to trim. The object clicked gets rimmed up to the nearest cutting edge or cutting edges. Moving Objects Command: M or Move. Menu: Modify  Move. To move objects, first select the objects to be moved. Then specify a base point. Finally choose a new position for the base point. OSNAP and OTRACK can assist in selecting the base point and specifying the second point of displacement. Copying Objects Command: CP or Copy. Menu: Modify  Copy. To copy objects, first select the objects to be copied. Then specify a base point. Finally choose a new position for the base point. OSNAP and OTRACK can assist in selecting the base point and specifying the second point of displacement. Arraying Objects Command: AR or Array. Menu: Modify  Array. A dialog box will assist in arraying the selected objects. Arrays can be rectangular or polar. Rectangular arrays will require you to specify rows and columns and he spacing between them.

Polar array will require you to specify centre point, angle to be filled, number of items, whether the objects must be rotated as they are copied and whether the original must be retained or erased. Mirroring Objects Command: MI or Mirror. Menu: Modify  Mirror. Select the items to be mirrored. Choose the mirror line. Specify whether to retain the original objects. It is not necessary that the mirror line must already be drawn, but it is easier if it is. Extending Objects Command: EX or Extend. Menu: Modify  Extend. Choose one or more boundary edges. Select the objects to extend. Filleting and Chamfering Command: Fillet and Chamfer. Menu: Modify  Fillet and Menu  Chamfer. For filleting, choose a filleting radius and the lines to be filleted. For chamfering, choose the chamfer distance and the lines to be chamfered.

Working with Layers Layers help you organize your drawing into separate layers and you can control the visibility of the layers to see more or les details. Using different layers for different floors, for electrical and sanitation details etc. can be very useful. Although layers imply two dimensions, in AutoCAD layers can be three dimensional. Each layer has a name, a default set of attributes for colour, line type, line weight and plot style. Further, it can be turned on or off, frozen or thawed, locked or unlocked. You can create new layers and delete existing layers. You can make any layer the current layer. All objects drawn are put into the current layer. When an object is drawn, its attributes are chosen to be the same as the default attributes of the current layer. The layer to which an object belongs can be changed using the object inspector. While turning off the current layer, you get a warning.

Working with Blocks Blocks are a collection of objects that are repeated a number of times within a drawing or in other drawings. Objects to be converted into a block are first drawn and then converted into a block (BLOCK). This operation requires the selection of objects to be converted into a block, a name for the block so that it can be used later and base point. Once a block is created, it can be inserted into the same drawing any number of times. Insertion requires the name of the block that is to be inserted, insertion point where the base point of the block will be placed, scaling factors along x and y directions and the rotation angle. To insert a block into other drawings, the block must first be written to a disk file (WBLOCK) and then inserted (INSERT) from there by specifying the name of he block file, which is a normal AutoCAD drawing file. A block can be exploded into its individual components with the command Explode.

Working with User Coordinate System The default coordinate system available when the drawing is created is called the World coordinate system. When the current coordinate system is the World coordinate system, you will see the letter “W” within the x-y axes. User Coordinate System (UCS) can be created by rotating the axes with reference to the World Coordinate System. With UCS, it is possible to draw along inclined lines or on the vertical plane. You can return to the World CS anytime using the command UCS.

Working with Text Multi line Text (MTEXT) Command: T or MTEXT. Menu: Draw  Text. Choose the style (Standard), Font, Text height, Font attributes (bold, italic, underline) and colour for the text. Text height is in the current units.

Text Styles To maintain uniformity of the text, you can create your own styles (Format  Text style). A style is a collection of text attributes and identified by a name you can choose. Once you define a set of text styles, you can choose the style while creating new text. It is possible to modify the style and then apply those changes to all text of that style. Text styles can also be used in defining Dimension styles.

Dimensioning Dimensioning can be done using the command DIM, in the horizontal (HOR), vertical (VER) or aligned (ALIGN) direction. You can choose a number of properties pertaining to Lines and Arrows (type and size), Text (Text styles will come in useful), Fit, Primary Units (precision), Alternate Units and Tolerances. A previous dimension can be continued (CONT). To draw a dimension, you need to pick the points and the dimension will be automatically displayed. Dimension Styles You can define a new dimension style from Format  Dimension style. To apply a different to a dimension that is already drawn, choose its Properties and change its style. You can make one of the Dimension styles as the default, and all new dimensions drawn will be of that style.

Plotting Before plotting, it is important to setup the paper size and orientation and the plotter device. This can be done in File  Page Setup  Plot Device. A model can be plotted from either the model space or the paper space. When plotting directly from the model space, you can choose the rectangular are of the model that you want to plot, choose a plotting scale, preview and then plot. Using Layout (paper space) to plot will give grater control on plotting. Layout Advantages of using layout to plot are: 1. A drawing can have multiple layouts for the same model, so that you can define different sizes and configurations of the plots prepared and choose the appropriate one while plotting. 2. Within a layout, you can define multiple viewports, control their size and position on the plot and choose the position and scale of the model visible within each viewport. 3. Any border and nameplate can be drawn on the layout at a 1:1 scale View Ports A view port in a layout can be created with the command VPORTS. A dialog box assists you in creating viewports with a number of pre-defined layouts. Simplest is the Single Viewport. Right clicking on the edge of the viewport and clicking properties brings up the Properties window. Here, choose the scale (Standard scale or Custom scale) for the contents of the viewport and other properties such as Layer, Linetype etc. All drawing commands are available in paper space just as in model space. To switch back and fort between paper space and model space, click on the PAPER button on the status bar. The border of the viewport changes to a thick line when you choose model space. In model space within a viewport you can zoom and pan just as in model space. Then switch back to paper space by clicking on MODEL on the status bar. Finally choose the scale to an exact number in the Properties window. Plotting When plotting using layout, always plot at a 1:1 scale. The scale for each viewport must be chosen separately, and it can be different for each viewport.

Working in Three Dimension Objects can be solids or surfaces in three dimension. Like the two dimensional primitives such as lines, circles and rectangles, AutoCAD has three dimensional solids and surfaces. The operations that can be performed on solids are Union, Subtraction, Intersect, Extrude. To view three dimensional objects, you will need to change the Viewpoint (VPOINT). Viewpoint coordinates -1,-1,1 is a good choice. Other ways of choosing the view point are View  3D Views  Viewpoint presets or View  3D views  Viewpoint. In 3D, you can ask AutoCAD to remove hidden lines or render.

Creating 3D Solids AutoCAD has a number of 3D solid primitives (Draw  Solids) such as Box, Cylinder, Sphere, Cone, Wedge, Torus. Another powerful technique of creating solids is to draw the cross section of the solid and extrude (EXTRUDE) it along a straight or curved path or revolve (REVOLVE) it about an axis. These options are available in the Draw  Solid menu. Modifying Solids Solid objects can be modified to create new solid objects through operations such as UNION (joining two or more objects which may or may not be touching one another), INTERSECT (retain only the portion common to two or more objects), SUBTRACT (removing a set of solids from a set of objects that will be retained). These operations are available from the Modify  Solids editing menu. It is possible to Array, Mirror or Rotate in 3D from the Modify  3D operation menu.