DRAW COMMANDS

Figure 4.1: Three methods of using draw commands entry

DRAW COMMANDS

4.1 Line

This is the fundamental drawing command. Use the line command to construct a line from one endpoint to the other. One or several line segments can be drawn with the line command. You can specify the endpoints of lines using two-dimensional or three-dimensional coordinates.

Draw toolbar :

Menu : Draw > Line

Command line : line or type “L”

From point: Specify a point or press ENTER to continue from the last line or arc To point: Specify a point

To point: Specify a point, enter u or undo, enter c or close, or press ENTER

AutoCAD draws a line segment and continues to prompt for points. You can draw a continuing series of line segments, but each line segment is a separate object. Press ENTER to end the command.

For example, the following command sequence draws a single line segment ( figure 4.2 ).

An arc is part of a circle; it is a regular curve of less than 360 degrees. The arc command in AutoCAD provides eleven options for creating arcs. An arc is one object. Arcs are always drawn by default in a counter-clockwise direction. An arc command can be reached by the following way

Draw toolbar :

Pull-down menu : Draw > arc

Command : arc

There are a number of ways to create arcs. The 3 points arc option is the default for the ARC command.

3 point arc

This command option identifies the location of the 3 points of the arc. We can use the keyboard and specify the coordinates or we may use the mouse to point the coordinates.

Figure 4.3

Start, Center, End

The radius is defined by the first two points that you specify.

Figure 4.4 Start, center, angle

The angle is the included angle between the sides from the center to the endpoints. A negative angle can be entered to generate an Arc in a clockwise direction.

Figure 4.5 : Start, Center, Length

Length means length of chord. The length of chord is between the start and the other point specified. A negative chord length can be entered to generate an arc of 180+ degrees.

Figure 4.6

Start, end, angle

The included angle is between the sides from the center to the endpoints. Negative angles generate clockwise arcs. The angle for figure below is 70 degrees.

Figure 4.7

Start, end, radius

The radius can be picked or entered as a value. A negative radius value generates arcs of 180+ degrees.

Figure 4.8

Start, end, direction

The direction is tangent to the start point.

end direction

start

Figure 4.9

Center, start, end

The option is like start, center, end but in a different order.

start end

center

Figure 4.10

Center, start, angle

This option is like start, center, angle but in a difference order.

angle

start

center

Figure 4.11 Center, start, length

This is similar to the start, center, length option but in a different order. Length means length of chord.

The new Arc continues from and is tangent to the last point. The only other point required is the endpoint of the arc. This method allows drawing arcs tangent to the preceding Line or Arc.

4.3 Circle

The CIRCLE command has many options, these include center, radius; center, diameter;

two points, three points; tangent, tangent, radius; tangent, tangent, tangent.

Draw toolbar :

Menu : Draw > Circle Command line : circle

Circle by Radius Mode:

Use the Circle command and the Radius mode to construct a circle by a radius value specified by the user. After selecting a center point for the circle, the user is prompted to enter a radius for the desired circle. Study the prompt below and illustration for constricting a circle using the Radius mode.

Command : CIRCLE

3P/2P/TTR/<Center Point> : ( Mark the center at ‘A’ ) Diameter/<Radius> : 1.50

Figure 4.13

Circle by Diameter Mode

Use the Circle command and the Diameter mode to construct a circle by a diameter value specified by the user. After selecting a center point for the circle, the user is prompted to enter a diameter for the desired circle. Study the prompt and illustration below for constructing a circle by using Diameter mode.

Figure 4.14

Command : CIRCLE

3P/2P/TTR/<Center Point> : ( Mark the center at ‘A’ ) Diameter/<Radius>: Diameter

Diameter : 3.00

3 Point Circle Mode:

Use the CIRCLE command and the 3 Point mode to construct a circle by 3 points identified by user. No center point is required when entering the 3 Point mode. Simply select three points and the circle is drawn. Study the prompt and illustration below for constructing a circle using the 3 Point mode.

Command : CIRCLE 3P/2P/TTR/<Center Point> : 3P

First Point : ( Select the Point at ‘A’ )

2 Point Circle mode:

Use the Circle command and the 2 Point mode to construct a circle by selecting 2 points.

These points will form the diameter of the circle. No center point is required after entering the 2 point mode. Study the prompt and illustration below for constructing a circle by using the 2 Point mode.

Command : CIRCLE

3P/2P/TTR/<Center Point> : 2P

First Point : ( Select the Point at ‘A’ ) Second point : ( Select the Point at ‘B’ )

Figure 4.16

Tangent-Tangent-Radius Mode - Method # 1:

This mode is very powerful when constructing a circle tangent to two entities. Illustrated below is an application of using the TTR mode to construct a circle tangent to two line segments. Study the prompt below to create this type of circle.

Command : CIRCLE

3P/2P/TTR/<Center Point> : TTR

Enter tangent spec : ( Select the line at ‘A’ )

Enter second tangent spec : ( Select the line at ‘B’ ) Radius : 1.4

B

( A )

A

( B )

Figure 4.17

Tangent-Tangent-Radius Mode : Method # 2:

Illustrated below is an application of using the Circle TTR mode to construct a circle tangent to the line segment on another circle. Study the prompt below to create this type of circle.

Command : CIRCLE

3P/2P/TTR/<Center Point> : TTR

Enter tangent spec : ( Select the line at ‘A’ )

Enter second tangent spec : ( Select the circle at ‘B’ ) Radius : 1.3

( B ) ( A )

Figure 4.18

Tangent-Tangent-Radius Mode : Method # 3:

Illustrated below is an application of using the Circle TTR mode to construct a circle tangent to another two circle. Study the prompt below to creating this type of circle.

Command : CIRCLE

3P/2P/TTR/<Center Point> : TTR

Enter tangent spec : ( Select the circle at ‘A’ )

Enter second tangent spec : ( Select the circle at ‘B’ ) Radius : 1.00

( A )

( B )

Figure 4.19

4.5 POINT

Use the point command to identify the location of a point on a drawing. This point may be used for reference purposes. The Osnap-Node or Nearest options are used to snap to points.

By default, a point is displayed as a dot on the screen. This dot may be confused with the existing grid dots already on the screen. To distinguish point entities from grid dots, use the chart at the right to assign a new point type; this is accomplished through the Pdmode system variable. Entering a value of 3 for Pdmode display the point as an ‘X’. The Pdsize system variable controls size of the point. Use the prompts below for changing the point mode to a value of 3.

Command : Pdmode

New value for variable PDMODE <0> : 3

Command : Point

Point : ( Mark the new position of a point using the cursor or one of the many coordinate systems )

Use the DDPTYPE dialog box below for dynamically selecting a new point mode and point size.

Figure 4.20 : Point Style dialog box

ACTIVITY 4a

ANSWER ALL THE QUESTIONS BELOW.

4.1 Draw the figure below with line, arc and circle command.

Figure 4.21

Figure 4.22