Modifying Commands (part 1)

Modifying commands

Introduction

The AutoCAD drawings are not completed simply by drawing the lines and circles. You need to modify these drawing objects in some ways so that you can create the objects you desire. AutoCAD provides almost all modify tools like Move, Erase, Rotate, Copy and so on. You can see that the command names are very easy to understand. However, the working way of these commands are not always obvious. This chapter will show you how all the Modifying commands work.

All these modifying tools can be accessed in 1 of 3 ways i.e. from the pull-down menu, from the keyboard and from the toolbar. You may use the method which makes you feel most comfortable and easy to use.

Usually the Modify toolbar is displayed by default. If it's not displayed by default then you may display it using the 'TOOLBAR' command or you can go from the pull-down menu i.e. View, Toolbars.... When the dialog box shown in above figure appears, check the box that is next to 'Modify' in the list of Toolbars option.

3.1 Erasing the Object

Command: Erase or E

The 'ERASE' command is one of the easiest AutoCAD commands & is used frequently. This command erases (or deletes) the selected objects from the drawing screen. Simply, you can get the same effect by selecting objects and hitting Delete key.

We can follow any of the following procedure to erase the object.

1. Choose Modify (from the menu bar), Erase

or

2. Click Erase icon (from the toolbar)

or

3. Type ERASE (at the command prompt)

command: ERASE

4. Pick the object to be deleted with the help of pick box.

Select object: (pick the object)

5. Press ENTER key when you are done choosing the objects to be erased.

Select objects: ENTER

If you want to delete (or, erase) the last obj. that you created you can type 'L' at the 'Select objects' prompt. Then, the last object will be highlighted & then you can select more objects or press 'ENTER' to end the command.

3.2 Creating multiple Objects

Drawing the same objects repeatedly for multiple times in same drawing area is not an efficient way to perform AutoCAD drawings. It is boring and time consuming as well. So, AutoCAD provides a set of commands to create multiple objects from one single object.

There are many ways of creating multiple objects. Some of them are listed below:

• Copy
• Offset
• Array
• Mirror and so on...

Copy Command:

The 'COPY' command is used to create 1 or more duplicates of any object or the objects that you have created in previous drawings. When you have to create very complex drawing elements, you don't want to redraw it again and again. So, this command is very worth and time saving command as you can simply copy that object as many times as you want.

Any of the following procedures can be followed.

1. Choose Modify (from the menu bar), Copy

or

2. Click the Copy icon (from the toolbar)

or

3. Type COPY (at the command prompt)

command: COPY

4. Pick objects to be copied

Select objects: (select with pick box)

5. Pick a point to move from.

Base point or displacement/Multiple: (pick point)

6. Pick a point where to copy the selected objects

Second point of displacement: (pick point)

(duplicate objects copied)

The option 'multiple' will allow you to create additional copies of the selected object simply by picking as many new points as you like. In order to end this multiple copy, you just need to press the 'ENTER' key.

Offset Command:

This command is probably 1 of the most worth and useful command to construct drawings. Using this command, we can copy the selected object at a certain distance in/out or, above/below that object. The new object is drawn according to the distance provided by the user and the direction chosen by the user with the help of a pick point. You can offset the objects such as arcs, lines, circles, rays , xlines, planar splines and so on.

Sequence of commands:

1. Type OFFESET (at the command prompt)

Command: OFFSET

2. Type The distance to copy the object)

Offset distance: (number)

3. Pick The object to offset

Select object to offset: (select object)

4. Pick A side to offset the object

Side to offset: (pick side)

5. Pick Another obj to offset

Select obj to offset: (pick side)

(Offsetting a straight line by specifying a distance)

Mirror Command:

It is used to mirror the selected object i.e. we can flip the objects about a given axis to create a symmetrical mirror image. Mirroring an object is useful to create symmetrical objects because we can create half of the object and then mirror the remaining half part(applicable only for the symmetrical objects) so that less time is consumed.

Sequence of Commands:

1. Choose Modify (from menu bar), mirror

or

2. Click the MIRROR icon from the toolbar

or

3. Type MIRROR (mirror at the command prompt)

Command: MIRROR or MI

4. Pick objects to mirror

Select objects: (select the obj to mirror)

5. Pick the 1st point of mirror line: (point)
6. Pick the 2nd point: (point)
7. Type "Yes" to delete the original objects and "No" to keep them

Delete old objects?( Y/ N):

Array Command:

The 'ARRAY' command creates many duplicate objects at a time. It makes multiple copies of the objects in a rectangular matrix (i.e. rows & columns) and a polar (i.e. circular) pattern. Basically, we also study two types of arrays, they are:

-Rectangular Array

-Polar Array

1. Rectangular Array:

For rectangular arrays, you can control the number of rows and columns and the distance between each rows and columns in a dialog box (Array).It is built along a baseline that is defined by the recent/current snap rotation angle. This included angle is 0 (zero) by default, so the rows& columns of a rectangular array are orthogonal w.r.t. (i.e. with respect to) the X & Y axes.

The illustration on the above figure shows the results after creating a rectangular array having 3 rows & 2 columns. In the given figure 'DR' indicates the distance between rows and 'DC' indicates the distance between columns. When you create a rectangular array it is essential to know that the new columns are created to the right of the original object and the new rows are created above the original object.

Now to draw rectangular array:

1. Choose Modify(from menu bar), Array

or

2. Click Array icon (from toolbar)

or

3. Type ARRAY (in the command line)

Command: ARRAY

(A dialog box appears, click on rectangular array)

4. Pick the object to array.
5. Type the no. of rows
6. Type the no. of columns
7. Type The unit cell distance between items in each row.

Distance between rows: ( + number=up, number =down)

8. Type the unit cell distance between items in each column.

Distance between columns:(+number=right, - number =left)

For instance:

Polar Array:

The working method of this polar array is similar to that of the rectangular array. The only difference is that in place of number and offset distance for rows & columns, you need to specify a centre point & the total no. of objects in the array. When you create a polar array, the array is drawn in clockwise or anti-clockwise direction, depending on whether you enter a positive or a negative value for the angle to fill.

To draw a polar array:

1. Choose Modify(from menu bar), ARRAY

or

2. Click the Array icon (from toolbar)

or

3. Type ARRAY (in the command line)

Command: ARRAY or AR

(A dialog box appears, click on polar array)

4. Pick objects to array

select objects: (select with pick box)

5. Type P to draw a polar array.
6. Pick a center point for the array.

the center point of the array: (pick point)

7. Type the total no. of items in the array.

number of items: (any number)

8. Type the no. of degrees to rotate the objects.

degrees to fill : (any number)

If you want to rotate the copied objects, then you can put the angle of rotation in the dialog box.

For instance:

The polar array looks just like the above figure. The illustration in above figure shows the result of a polar array by using an original circle copied eight times about a center point, through an angle 360 degrees.