Chapter 4. Part 1 AutoCAD Basics Chapter Objectives Describe the AutoCAD screen layout. Perform an AutoCAD drawing setup, including setting units, limits, layers, linetypes, and lineweights. Explain the coordinate systems used to create AutoCAD drawings (absolute, relative, and polar coordinates). Create and edit AutoCAD drawings using the commands found on the Draw, Modify, and Inquiry toolbars. Employ object snaps to facilitate construction of AutoCAD drawings. Use the Properties tool to inquire about or to change the properties of an entity. Add text to a drawing and edit the text including text style. Create a floor plan for a small cottage. Create multiview drawings of machine parts. Plot AutoCAD drawings.
Beginning an AutoCAD Drawing The AutoCAD Interface Title Bar Vertical Scroll Bar Drawing Window Cursor User Coordinate System Icon (UCS Icon) Horizontal Scroll Bar Command Line
AutoCAD s Ribbon Interface Figure 4.2 The AutoCAD Ribbon User Interface
AutoCAD s Ribbon Interface with DRAW, MODIFY, DIMENSION and Object SNAP Toolbars displayed. Tools Menu Bar Opening the Toolbars 1. Type MENUBAR on the command line and press <Enter>. At the prompt type 1 and press <Enter>. 2. Pick Tools on the menu bar. Select Toolbars, AutoCAD, and pick Draw. This will open the Draw toolbar. 3. Repeat the first two steps to open the Modify, Dimension, and Object Snap toolbars. 4. Drag each toolbar by left-clicking on the dark gray bars at either end of a toolbar and holding down the left-click button. Drag the toolbar to the side of the screen and dock it. AutoCAD Toolbars (shown in docked position) menubar
Creating, Opening, and Saving AutoCAD Drawing Files. Application Button Application Menu
Workspace Switching and AutoCAD Classic Workspace Switching Drop-down Menu Standard Toolbar Layers Toolbar Properties Toolbar Modify Toolbar Draw Toolbar Workspaces can also be switched by selecting the gear button in the lower right corner of the screen and selecting AutoCAD Classic.
Drawing a LINE with AutoCAD (Dynamic Input is ON) Angle Input Dynamic Prompt Length Input The current input field has a dark blue background. If entering an X and Y value to define of the endpoint of the next line, enter the X coordinate first, then type a comma and enter the Y coordinate, then press Enter. If entering a length and an angle to define the end of the next line, enter the length first, then press the Tab key, and enter the angle, then press Enter. Ortho Button When Ortho is on, the cursor can only move horizontally or vertically while the Line command. This is very useful when you want to draw lines that are perfectly horizontal or vertical. The line shown above could not have been drawn at an angle if Ortho had been on.
Quick Review of Points, Planes, and Lines Points A point is an exact location in space that is defined by coordinates that are located relative to a known origin point. Points are often represented in technical drawings by a visible dot, and while the dot representing a point is visible, the point has no dimensional size. Locating Points in Two Dimensional (2D) Coordinate Systems In a two dimensional (2D) coordinate system, points are defined on a 2D flat surface that represents a plane. The coordinates of the point are located by measuring from two perpendicular lines that represent the X (horizontal) and Y (vertical) axes. The intersection where the X and Y axes meet is called the origin. In technical drawings, the X and Y axes represent a 2D area referred to as the XY plane. In the example below, the origin point s value would be stated as zero comma zero, or (0,0), which means the location of the origin is zero units (0) on the X axis and zero units (0) on the Y axis. A point, represented by a green dot, is located at coordinate 2,3. This means that the point s location is 2 units to the right of the origin on the X axis and 3 units above the origin on the Y axis. Point located at 2,3 Note: Coordinates that are defined relative to a 0,0 origin are also referred to as absolute coordinates. Origin (0,0)
AutoCAD coordinates are based on the Cartesian Coordinate system. In the example below, two points (in red) are defined on the XY plane at coordinates 1,2 and 4,3 respectively. Origin Point (0,0) Points that lie on the same plane are referred to as coplanar. Points that share the same location are referred to as coincident.
Negative Values in Two Dimensional (2D) Coordinate Systems Points that are located below the X axis, or to the left of the Y axis, are described with negative coordinate values (a minus sign precedes the coordinate). In the example below, two points are defined at coordinates -3,1 and -1.5,-2.5 respectively. Origin Point (0,0)
Three Dimensional (3D) Coordinate Systems In a three dimensional (3D) coordinate system, a Z axis is added to the X and Y axes. Using this system, points can be located relative to the origin along the X, Y and Z axes. The Z axis represents the height of the point above or below the X,Y plane (see figure below). For example, a 3D coordinate might be defined with the coordinates 1,1,1. This coordinate would lie one unit to the right of the origin along the X axis, one unit from the origin along the Y axis, and one unit above the X,Y plane. Origin Point (0,0,0) of a 3D coordinate system
Lines To a mathematician, a line is a set of continuous points that extend indefinitely in either direction. In technical drawing terminology, a line is a segment defined by two endpoints. The endpoints are defined with coordinates. Points that lie on the same line are referred to as collinear. Noncollinear points do not lie on the same line. In the example below, a red line begins at a start point located at coordinate 2,2 and ends at a point located at coordinate 8,7 (relative to the origin). These point are collinear. A point located exactly halfway between the start and end points would be the line s midpoint.
Angles Angle An angle is formed when two, noncollinear lines have the same endpoint. The angle at right is formed by sides BA and BC. The angle formed by these lines is referred to as angle ABC. Vertex In 2D space, the common point where two lines meet is called a vertex. The plural of vertex is vertices. In the example at right, angle ABC s vertex is point B and the its sides are lines BA and BC. Note: When specifying an angle using letters or numbers, the vertex should be the middle letter in the series. Note: The point where two lines cross is referred to as an intersection - as opposed to a vertex. In 3D objects, a vertex is where the object s edges meet. In the object at right, all of the vertices have been assigned a number. This object has a total of 17 vertices.
The User Coordinate System (UCS) Icon 0,0 point in the AutoCAD graphics window. Y X
Drawing Lines with Absolute Coordinates 0,0
Draw a Line with Absolute Coordinates
Relative Coordinates You will usually begin a drawing with an absolute coordinate followed by relative coordinates.
Draw a Line with Relative Coordinates
Angles in AutoCAD To lay out a 45 degree angle in AutoCAD, you would begin at East (0 degrees) and turn counterclockwise 45 degrees.
Polar Coordinates When entering Polar Coordinates with Dynamic Input ON, type the distance and then pick tab to enter the degree. When Dynamic Input is OFF, type the at sign @ to indicate a relative polar coordinate, then the distance required, and finally, the less than symbol followed by the degree (@2.25<60).
Draw a Line with Polar Coordinates
Direct Entry Horizontal Line In this example, the drafter turned Ortho on and began a line at 1,1, then moved the cursor to the right (or positive X), typed in 2.5, and pressed Enter. The resulting horizontal line was drawn 2.5 units to the right of the start point.
Direct Entry Vertical Line In this example the drafter continued the line by moving the mouse in the positive Y direction (or up), typing 2, and pressing Enter.
Exercise 4-1 Directions: Begin a new AutoCAD drawing (default to the acad.dwt template). Using the LINE command and the coordinate entry methods described earlier, draw the object shown in Figure 4-17. Begin the bottom left corner of the object at absolute coordinate 2,2 and draw the first line in the positive X direction. Continue drawing lines until you are unable to continue due to lack of coordinate information (21 contiguous lines total). At this point, begin a new line from absolute coordinate 2,2 and draw in the positive Y direction. Continue drawing lines in this manner until you are unable to continue due to lack of coordinate information (4 contiguous lines total). To complete the drawing, draw a line connecting the endpoints of the two sets of lines. If you need assistance with this exercise, ask your instructor for help.
End AutoCAD Basics Part 1