UNIT 4
DRAWING USING CAD SOFTWARE
Circle
Toolbar---Draw---Circle
Pull-down---Draw--- Circle Center, Radius
Keyboard---CIRCLE -short-cut C
The Circle command is used to draw circles. There are a number of ways you can define the circle. The default method is to pick the centre point and then to either pick a second point on the circumference of the circle or enter the circle radius at the keyboard.
As you can see from the command prompt above the default options are always indicated in triangular brackets like so <Default> and command options appear within square brackets like so [Option]. Each option is separated by a forward slash like this /. You can choose to use the alternative options by typing them at the prompt. For example, the circle command gives you three extra options to define a circle. 3P which uses any three points on the circumference, 2P which uses two points on the circumference to form a diameter and Ttr which stands for Tangent Tangent Radius. Obviously to use this last option you need to have drawn two lines which you can use as tangents to the circle. Try these options out to see how they work. Note that to invoke a command option, you need only type the upper-case part of the option name. For example, if you want to use the Ttr option, you need only enter "T". There are two more circle options on the pull-down menu that enable you to draw a circle by defining the center and diameter or by using 3 tangents.
Arcs
Toolbar---Draw---Arc
Pull-down---DrawArc3 Points
Keyboard ARC short-cut A
The Arc command allows you to draw an arc of a circle. There are numerous ways to define an arc, the default method uses three pick points, a start points, a second point and an end point. Using this method, the drawn arc will start at the first pick point, pass through the second point and end at the third point. Once you have mastered the default method try some of the others. You may, for example need to draw an arc with a specific radius. All of the Arc command options are available from the pull-down menu.
Rectangle
Toolbar---Draw--Rectangle
Pull-down—-Draw Rectangle
Keyboard RECTANGLE short-cuts REC, RECTANG
The Rectangle command is used to draw a rectangle whose sides are vertical and horizontal. The position and size of the rectangle are defined by picking two diagonal corners. The rectangle isn't really an AutoCAD object at all. It is, in fact, just a closed polyline which is automatically drawn for you.
Polygon
Toolbar---Draw---Polygon
Pull-down---Draw Polygon
Keyboard POLYGON short-cut POL
The Polygon command can be used to draw any regular polygon from 3 sides up to 1024 sides. This command requires four inputs from the user, the number of sides, a pick point for the centre of the polygon, whether you want the polygon inscribed or circumscribed and then a pick point which determines both the radius of this imaginary circle and the orientation of the polygon. The polygon command creates a closed polyline in the shape of the required polygon.
This command also allows you to define the polygon by entering the length of a side using the Edge option. You can also control the size of the polygon by entering an exact radius for the circle. Follow the command sequence below to see how this command works.
Ellipse
Toolbar---Draw---Ellipse
Pull-down---Draw Ellipse Axis, End
Keyboard ELLIPSE short-cut EL
The Ellipse command gives you a number of different creation options. The default option is to pick the two end points of an axis and then a third point to define the eccentricity of the ellipse. After you have mastered the default option, try out the others.
Spline
Toolbar---Draw---Spline
Pull-down---Draw Spline
Keyboard SPLINE short-cut SPL
Tolerance the Spline command creates a type of spline known as a non uniform rational B-spline, NURBS for short. A spline is a smooth curve that is fitted along a number of control points. The Fit Tolerance option can be used to control how closely the spline conforms to the control points. A low tolerance value causes the spline to form close to the control points. A tolerance of 0 (zero) forces the spline to pass through the control points. The illustration on the right shows the effect of different tolerance values on a spline that is defined using the same four control points, P1, P2, P3 and P4.
Splines can be edited after they have been created using the SPLINEDIT command, Modify Object Spline from the pull-down menu. Using this command, you can change the tolerance, add more control points move control points and close splines, amongst other things. However, if you just want to move spline control points, it is best to use grips. See the Stretching with Grips section of the Modifying Objects tutorial for details.
Poly-Line
Toolbar---Draw---Polyline
Pull-down---Draw Polyline
Keyboard PLINE short-cut PL
The Polyline or Pline command is similar to the line command except that the resulting object may be composed of a number of segments which form a single object. In addition to the two ends a polyline is said to have vertices (singular vertex) where intermediate line segments join. In practice the Polyline command works in the same way as the Line command allowing you to pick as many points as you like. Again, just hit Return to end. As with the Line command, you also have the option to automatically close a polyline end to end. To do this, type C to use the close option instead of hitting Return. Follow the command sequence below to see how this works.
Multi-Line
Multi lines are complex lines that consist of between 1 and 16 parallel lines, known as elements. The default multiline style has just two elements but you can create additional styles of an almost endless variety. The Multiline Style command enables you to create new multiline styles by adding line elements, changing the color and line type of elements, adding end caps and the option of displaying as a solid color.
Toolbar---custom---Multiline
Pull-down---Draw Multiline
Keyboard MLINE short-cut ML
The Multiline command is used to draw multi lines. This process of drawing is pretty much the same as drawing poly lines, additional line segments are added to the multiline as points are picked. As with poly lines, points can be unpicked with the Undo option and multi lines can be closed.
When you start the Multiline command you also have the option to specify the Justification, Scale and Style of the multiline. The Justification option allows you to set the justification to "Top", the default, "Zero" or "Bottom". When justification is set to top, the top of the multiline is drawn through the pick points, as in the illustration below. Zero justification draws the centre line of the multiline through the pick points and Bottom draws the bottom line through the pick points. Justification allows you to control how the multiline is drawn relative to your setting out information. For example, if you are drawing a new road with reference to its centre line, then Zero justification would be appropriate.
The Scale option allows you to set a scale factor, which effectively changes the width of the multiline. The default scale factor is set to 1.0 so to half the width of the multiline, a value of 0.5 would be entered. A value of 2.0 would double the width.
The Style option enables you to set the current multiline style. The default style is called "Standard". This is the only style available unless you have previously created a new style with the Multiline Style command. Follow the command sequence below to see how the Multiline command works and then try changing the Justification and Scale options.
TRIM projects the cutting edges and the objects to be trimmed onto the XY plane of the current user coordinate system (UCS). Note: To select cutting edges that include blocks, you can use only the single selection, Crossing, Fence, and Select All options. Select objects. Specifies objects individually.
To trim objects, select the boundaries and press Enter. Then select the objects that you want to trim. To use all objects as boundaries, press Enter at the first Select Objects prompt.
Move, copy, Rotate
- Click Home tab
Modify panel
Move, Copy, and Rotate drop-down
Copy, Move then Rotate. 
Find - In the drawing area, select the object to copy and press ENTER.
- Select the point around which to rotate the object.
- In the drawing area, click to indicate the position to which you want to move the object.
- In the command line, specify the angle to rotate or in the drawing area, or click to indicate the new position.
- Press ENTER.
Fillet
Toolbar---Modify---Fillet
Pull-down---Modify Fillet
Keyboard FILLET short-cut F
The Fillet command is a very useful tool which allows you to draw an arc between two intersecting lines or adjacent polyline segments. You first need to use the command to set the required radius and then a second time to select the two lines.
Chamfer
Toolbar---Modify---Chamfer
Pull-down---Modify Chamfer
Keyboard CHAMFER short-cut CHA
The Chamfer command enables you to create a chamfer between any two non-parallel lines as in the illustration below or any two adjacent polyline segments. Usually, the Chamfer command is used to set the chamfer distances before drawing the chamfer. Follow the command sequence below where the chamfer distances are changed to 20 before the chamfer is made.
Stretch
Toolbar---Modify---Stretch
Pull-down---Modify Stretch
Keyboard STRETCH short-cut S
The Stretch command can be used to move one or more vertices of an object whilst leaving the rest of the object unchanged. In the example below, a rectangle has been stretched by moving one vertex to create an irregular shape.
Scale
Toolbar---Modify---Scale
Pull-down---Modify Scale
Keyboard SCALE short-cut SC
The Scale command can be used to change the size of an object or group of objects. You are prompted for a pick point about which the selection set will be scaled. Scaling can then be completed by picking a second point (not always easy because it can sometimes be difficult to precisely control the scaling) or by entering a scale factor at the keyboard. For example, a scale factor of 2 will double the size of the objects in the selection set and a factor of 0.5 will half them.
Array
Toolbar---Modify---Array
Pull-down---Modify Array
Keyboard ARRAY short-cut AR
The Array command makes multiple copies of selected objects in a rectangular matrix (columns and rows) or a polar (circular) pattern. This command has been completely transformed in AutoCAD 2000i. It is now completely dialogue box driven with the option to see a preview of the array before it is created. You can also now create rectangular arrays at a user specified angle example, this constitutes a major improvement in usability.
Now start the Array command. First of all, make sure that the Rectangular Array radio button is selected and that you are looking at the Rectangular Array dialogue box and now follow the steps below:
Click the Select objects button. The dialogue box will temporarily disappear enabling you to select the rectangle you just drew. Press the Return button on your keyboard to complete the selection. You are now returned to the dialogue box and the message immediately below the Select Objects button should read "1 objects selected".
Enter the number of rows required in the Rows edit box. For this example, enter the value "3". Notice that the schematic preview on the right hand side of the dialogue box updates to reflect the values you are entering.
Enter the number of columns required in the Columns edit box. Enter the value "2".
Enter the row offset in the Row Offset edit box. This is the distance DR in the illustration above. Note that this is not the distance between rows. In this example, our rectangle is 10 units high and we will enter a row offset of 15. The result will be a 5 unit gap between rectangles.
Enter the column offset in the Column Offset edit box. The same parameters apply as for the row offset. Enter a value of 25 to give a 5 unit gap between our rectangles.
Click on the Preview button. Once again, the dialogue box disappears and the specified array is temporarily drawn so that we can preview it. We are now offered 3 choices. If the array isn't quite right, click the Modify button to return to the Array dialogue box. If you are happy with the array, click the Accept button, the array will be permanently drawn and the command is ended.
You should now have an array that looks similar to the one in the illustration above consisting of 6 rectangles arranged in 3 rows and 2 columns. As you can see, this command is very powerful and can save lots of time if used carefully.
Offset
Toolbar---Modify---Offset
Pull-down---Modify Offset
Keyboard OFFSET short-cut O
Offset is probably one of the most useful commands for constructing drawings. The Offset command creates a new object parallel to or concentric with a selected object. The new object is drawn at a user defined distance (the offset) from the original and in a direction chosen by the user with a pick point. You can offset lines, arcs, circles, ellipses, 2D poly lines, x lines, rays and planar splines.
Mirror
Toolbar---Modify---Mirror
Pull-down---Modify Mirror
Keyboard MIRROR short-cut MI
The Mirror command allows you to mirror selected objects in your drawing by picking them and then defining the position of an imaginary mirror line using two points.
AutoCAD provides a whole range of dimensioning tools which can be used to quickly dimension any drawing without the need for measurement. Dimensioning in AutoCAD is automatic; lines, arrows and text are all taken care of by the dimension commands. AutoCAD dimensions are special blocks which can easily be edited or erased as necessary.
AutoCAD provides lots of control over the way dimensions look. Using a system similar to text styles, dimension styles allow you to design dimensions so that they look just the way you want them to.
The Linear Dimension Command
The Continue Dimension Command
The Baseline Dimension Command
The Aligned Dimension Command
