Randy H. Shih
AutoCAD 2014
Tutorial - First Level:
2D Fundamentals
®
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Manual de autocad 2014, Apuntes de Arquitectura
Manual de autocad 2014
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2015/2016
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Randy H. Shih
AutoCAD 2014
Tutorial - First Level:
2D Fundamentals
®
www.SDCpublications.com
P U B L I C A T I O N S^ SDC^ Better Textbooks. Lower Prices.
Schroff Development Corporation
Multimedia Disc
Video presentations of selected tutorials and exercises
Visit the following websites to learn more about this book:
1-2 AutoCAD®^ 2014 Tutorial: 2D Fundamentals
AutoCAD Certified User Examination Objectives Coverage
This table shows the pages on which the objectives of the Certified User Examination are covered in Chapter 1.
- Precision...........................................................................1- Section 1: Controlling the Display in Drawings
- Zoom Extent.....................................................................1-
- Drawing LIMITS ............................................................1-
- Status Bar .........................................................................1-
- GRID Display ..................................................................1-10, 1-
- PAN Realtime ..................................................................1-
- Format ..............................................................................1- Section 2: Creating Basic Drawings
- Units Setup ......................................................................1-
- LINE Command ...............................................................1-
- Coordinates ......................................................................1-
- Interactive Input Method..................................................1-
- SNAP Option ...................................................................1-
- World Space .....................................................................1-
- User Coordinate System ..................................................1-
- World Coordinate System ................................................1-
- UCS Icon Display ............................................................1-
- TTR, Circle ......................................................................1-
- Relative Coordinate .........................................................1-
- Coordinate Systems .........................................................1-
- Cartesian coordinate system ............................................1-
- Absolute Coordinates .......................................................1-17, 1-
- Positions, Defining...........................................................1-
- LINE, Close Option .........................................................1-
- CIRCLE Command ..........................................................1-
- TTT, Circle ......................................................................1-
- ARC Command ………………………………………... 1-
- ERASE Command ..........................................................1- Section 3: Manipulating Objects
- Selection Window ............................................................1-
AutoCAD Fundamentals 1-
Introduction
Learning to use a CAD system is similar to learning a new language. It is necessary to begin with the basic alphabet and learn how to use it correctly and effectively through practice. This will require learning some new concepts and skills as well as learning a different vocabulary. Today, the majority of the Mechanical CAD systems are capable of creating three-dimensional solid models. Nonetheless, all CAD systems create designs using basic geometric entities and many of the constructions used in technical designs are based upon two-dimensional planar geometry. The method and number of operations that are required to accomplish the basic planar constructions are different from one system to another.
In order to become effective and efficient in using a CAD system, we must learn to create geometric entities quickly and accurately. In learning to use a CAD system, lines and circles are the first two, and perhaps the most important two, geometric entities that one should master the skills of creating and modifying. Straight lines and circles are used in almost all technical designs. In examining the different types of planar geometric entities, the importance of lines and circles becomes obvious. Triangles and polygons are planar figures bounded by straight lines. Ellipses and splines can be constructed by connecting arcs with different radii. As one gains some experience in creating lines and circles, similar procedures can be applied to create other geometric entities. In this chapter, the different ways of creating lines and circles in AutoCAD®^2014 are examined.
Starting Up AutoCAD
®
- Select the AutoCAD 2014 option on the Program menu or select the AutoCAD 2014 icon on the Desktop.
Once the program is loaded into memory, the AutoCAD®^2014 drawing screen will appear on the screen.
AutoCAD Fundamentals 1-
Drawing Units Setup
Every object we construct in a CAD system is measured in units. We should determine the system of units within the CAD system before creating the first geometric entities.
- In the Menu Bar select: [Format] [Units]
- The AutoCAD Menu Bar contains multiple pull-down menus, where all of the AutoCAD commands can be accessed. Note that many of the menu items listed in the pull-down menus can also be accessed through the Quick Access toolbar and/or Ribbon panels.
- Click on the Length Type option to display the different types of length units available. Confirm the Length Type is set to Decimal.
- On your own, examine the other settings that are available.
- In the Drawing Units dialog box, set the Length Type to Decimal. This will set the measurement to the default English units, inches.
1-6 AutoCAD®^ 2014 Tutorial: 2D Fundamentals
- Set the Precision to two digits after the decimal point as shown in the above figure.
- Pick OK to exit the Drawing Units dialog box.
Drawing Area Setup
Next, we will set up the Drawing Limits by entering a command in the command prompt area. Setting the Drawing Limits controls the extents of the display of the grid. It also serves as a visual reference that marks the working area. It can also be used to prevent construction outside the grid limits and as a plot option that defines an area to be plotted/printed. Note that this setting does not limit the region for geometry construction.
- In the Menu Bar select: [Format] [Drawing Limits]
- In the command prompt area, the message “Reset Model Space Limits: Specify lower left corner or [On/Off] <0.00,0.00>:” is displayed. Press the ENTER key once to accept the default coordinates <0.00,0.00>.
- In the command prompt area, the message “Specify upper right corner <12.00,9.00>:” is displayed. Press the ENTER key again to accept the default coordinates <12.00,9.00>.
1-8 AutoCAD®^ 2014 Tutorial: 2D Fundamentals
Drawing Lines with the LINE Command
- Move the graphics cursor to the first icon in the Draw panel. This icon is the Line icon. Note that a brief description of the Line command appears next to the cursor.
- Select the icon by clicking once with the left- mouse-button, which will activate the Line command.
- In the command prompt area, near the bottom of the AutoCAD drawing screen, the message “_line Specify first point:” is displayed. AutoCAD expects us to identify the starting location of a straight line. Move the graphics cursor inside the graphics window and watch the display of the coordinates of the graphics cursor at the bottom of the AutoCAD drawing screen. The three numbers represent the location of the cursor in the X, Y, and Z directions. We can treat the graphics window as if it was a piece of paper and we are using the graphics cursor as if it were a pencil with which to draw.
We will create a freehand sketch of a five- point star using the Line command. Do not be overly concerned with the actual size or accuracy of your freehand sketch. This exercise is to give you a feel for the AutoCAD®^2014 user interface.
Coordinates of the graphics cursor
5
3 2
1 4
AutoCAD Fundamentals 1-
- We will start at a location about one-third from the bottom of the graphics window. Left-click once to position the starting point of our first line. This will be point 1 of our sketch. Next move the cursor upward and toward the right side of point
- Notice the rubber-band line that follows the graphics cursor in the graphics window. Left-click again (point 2) and we have created the first line of our sketch.
- Move the cursor to the left of point 2 and create a horizontal line about the same length as the first line on the screen.
- Repeat the above steps and complete the freehand sketch by adding three more lines (from point 3 to point 4, point 4 to point 5, and then connect to point 5 back to point 1).
- Notice that the Line command remains activated even after we connected the last segment of the line to the starting point (point 1) of our sketch. Inside the graphics window, click once with the right-mouse-button and a popup menu appears on the screen.
- Select Enter with the left-mouse-button to end the Line command. (This is equivalent to hitting the [ENTER] key on the keyboard.)
- Move the cursor near point 2 and point 3, and estimate the length of the horizontal line by watching the displayed coordinates for each point.
5
3 2
1 4
AutoCAD Fundamentals 1-
GRID ON
- Left-click the GRID button in the Status Bar to turn ON the GRID DISPLAY option. (Notice in the command prompt area, the message “
” is also displayed.) - Move the cursor inside the graphics window, and estimate the distance in between the grid lines by watching the coordinates displayed at the bottom of the screen.
The GRID option creates a pattern of lines that extends over an area on the screen. Using the grid is similar to placing a sheet of grid paper under a drawing. The grid helps you align objects and visualize the distance between them. The grid is not displayed in the plotted drawing. The default grid spacing, which means the distance in between two lines on the screen, is 0.5 inches. We can see that the sketched horizontal line in the sketch is about 4.5 inches long.
1-12 AutoCAD®^ 2014 Tutorial: 2D Fundamentals
SNAP MODE ON
- Left-click the SNAP MODE button in the Status Bar to turn ON the SNAP option.
- Move the cursor inside the graphics window, and move the cursor diagonally on the screen. Observe the movement of the cursor and watch the coordinates display at the bottom of the screen.
The SNAP option controls an invisible rectangular grid that restricts cursor movement to specified intervals. When SNAP mode is on, the screen cursor and all input coordinates are snapped to the nearest point on the grid. The default snap interval is 0.5 inches, and aligned to the grid points on the screen.
- Click on the Line icon in the Draw toolbar. In the command prompt area, the message “_line Specify first point:” is displayed.
- On your own, create another sketch of the five-point star with the GRID and SNAP options switched ON.
- Use the right-mouse-button and select Enter in the popup menu to end the Line command if you have not done so.
1-14 AutoCAD®^ 2014 Tutorial: 2D Fundamentals
Repeat the Last Command
- Inside the graphics window, click once with the right-mouse- button to bring up the popup option menu.
- Pick Repeat Erase, with the left-mouse-button, in the popup menu to repeat the last command. Notice the other options available in the popup menu.
AutoCAD®^2014 offers many options to accomplish the same task. Throughout this text, we will emphasize the use of the AutoCAD Heads-up DesignTM^ interface, which means we focus on the screen, not on the keyboard.
- Move the cursor to a location that is above and toward the left side of the entities on the screen. Left-mouse-click once to start a corner of a rubber-band window.
- Move the cursor toward the right and below the entities, and then left-mouse-click to enclose all the entities inside the selection window. Notice all entities that are inside the window are selected.
- Inside the graphics window, right-mouse-click once to proceed with erasing the selected entities.
On your own, create a free-hand sketch of your choice using the Line command. Experiment with using the different commands we have discussed so far. Reset the status buttons so that only the GRID DISPLAY option is turned ON as shown.
Second corner
First corner
AutoCAD Fundamentals 1-
The CAD Database and the User Coordinate System
Designs and drawings created in a CAD system are usually defined and stored using sets of points in what is called world space. In most CAD systems, the world space is defined using a three-dimensional Cartesian coordinate system. Three mutually perpendicular axes usually referred to as the X-, Y-, and Z-axes, define this system. The intersection of the three coordinate axes forms a point called the origin. Any point in world space can then be defined as the distance from the origin in the X-, Y- and Z- directions. In most CAD systems, the directions of the arrows shown on the axes identify the positive sides of the coordinates.
A CAD file, which is the electronic version of the design, contains data that describes the entities created in the CAD system. Information such as the coordinate values in world space for all endpoints, center points, etc., along with the descriptions of the types of entities are all stored in the file. Knowing that AutoCAD stores designs by keeping coordinate data helps us understand the inputs required to create entities.
The icon near the bottom left corner of the default AutoCAD graphics window shows the positive X-direction and positive Y-direction of the coordinate system that is active. In AutoCAD, the coordinate system that is used to create entities is called the user coordinate system (UCS). By default, the user coordinate system is aligned to the world coordinate system (WCS). The world coordinate system is a coordinate system used by AutoCAD as the basis for defining all objects and other coordinate systems defined by the users. We can think of the origin of the world coordinate system as a fixed point being used as a reference for all measurements. The default orientation of the Z-axis can be considered as positive values in front of the monitor and negative values inside the monitor.
3D UCS icon
AutoCAD Fundamentals 1-
Cartesian and Polar Coordinate Systems
In a two-dimensional space, a point can be represented using different coordinate systems. The point can be located, using a Cartesian coordinate system, as X and Y units away from the origin. The same point can also be located using the polar coordinate system, as r and θ units away from the origin.
For planar geometry, the polar coordinate system is very useful for certain applications. In the polar coordinate system, points are defined in terms of a radial distance, r, from the origin and an angle θ between the direction of r and the positive X axis. The default system for measuring angles in AutoCAD®^2014 defines positive angular values as counter-clockwise from the positive X-axis.
Absolute and Relative Coordinates
- AutoCAD®^2014 also allows us to use absolute and relative coordinates to quickly construct objects. Absolute coordinate values are measured from the current coordinate system's origin point. Relative coordinate values are specified in relation to previous coordinates.
Note that the coordinate display area can also be used as a toggle switch; each left- mouse-click will toggle the coordinate display on or off.
In AutoCAD®^2014 , the absolute coordinates and the relative coordinates can be used in conjunction with the Cartesian and polar coordinate systems. By default, AutoCAD expects us to enter values in absolute Cartesian coordinates, distances measured from the current coordinate system's origin point. We can switch to using the relative coordinates by using the @ symbol. The @ symbol is used as the relative coordinates specifier, which means that we can specify the position of a point in relation to the previous point.
1-18 AutoCAD®^ 2014 Tutorial: 2D Fundamentals
Defining Positions
In AutoCAD, there are five methods for specifying the locations of points when we create planar geometric entities.
Interactive method: Use the cursor to select on the screen.
Absolute coordinates (Format: X,Y): Type the X and Y coordinates to locate the point on the current coordinate system relative to the origin.
Relative rectangular coordinates (Format: @X,Y): Type the X and Y coordinates relative to the last point.
Relative polar coordinates (Format: @Distance<angle): Type a distance and angle relative to the last point.
Direct Distance entry technique: Specify a second point by first moving the cursor to indicate direction and then entering a distance.
GRID Style Setup
- In the Status Bar area, right-mouse-click on SnapMode and choose [Settings].
- In the Drafting Settings dialog box, select the Snap and Grid tab if it is not the page on top.
- Change Grid Style to Display dotted grid in 2D model Space as shown in the below figure.
- Pick OK to exit the Drafting Settings dialog box.