This chapter illustrates techniques by which you can manipulate drawing objects. It illustrates how to erase, move, copy, rotate, enlarge and reduce drawing objects. You will also learn how to use the edit functions as a drawing aid tool to make quick corrections.

The chapter ends with a read-through exercise that illustrates the basic steps to draw an engineer’s office and an engineering complex plan.

Changes that may look extremely difficult on a drawing board can be easily accomplished with CADD. Even if you have to make a major change, chances are that you won't have to redraw it from scratch. You can manipulate the diagrams in a number of ways and may be able to rearrange the existing pieces of the drawing to fit the new shape.

The following are the basic capabilities of the edit module:
 

Note:

The erase function is very powerful; it must be used with great caution. It can erase large amounts of information within seconds. If you make a mistake while erasing, be sure to take quick action. You can use the undo feature of CADD to instantly disregard the effect of the last command. Do not go any further with the mistake; it will only make it more difficult to fix the drawing.
 

To move the objects, the first step is to select the objects that are to be moved. The second step is to indicate a base point. The base point acts as an anchor for the selected objects. Finally, indicate a relocation point (or destination point). The relocation point determines the new location of the selected objects. All the objects are moved relative to the base point and the relocation point. Let's say you indicate the relocation point 4'-0" to the right of the base point. All the selected objects will be moved 4'-0" to the right.
 

Using the copy function is quite similar to the way the move function is used. First, you need to select objects using any of the methods described earlier. Then you need to indicate a base point and a relocation (or destination) point. The copied objects are placed according to the relocation point.

Making Multiple Copies in a Rectangular Form

There are separate functions available in CADD that allow you to make multiple copies in a linear or rectangular fashion (commonly known as a rectangular array). You can make hundreds of copies within seconds. You don't need to enter a base point and a destination point. You just need to select the objects, specify how many rows and columns you need and the distance between them.

Making Copies in a Circular Form

CADD allows you to make multiple copies of selected objects in a circular fashion (commonly known as a polar array). You need to enter the center point of array, number of copies required and the rotation angle. The center point of the array is a point around which the copies are arranged. The rotation angle determines the extent of the rotation, and the number of copies you specify are equally spaced between the rotation angle.
 

When you enter a command to change the drawing appearance, you are prompted to select the objects you want to change. You can select the objects using any of the methods discussed earlier. After the selection is made, you can specify what you want to change, and the selected objects are changed accordingly.

The edit functions allow you to do the following:
 

Cutting Drawing Objects Along an Edge

CADD allows you to erase drawing objects along a selected edge (this technique is often called trimming). When you use this function, you are prompted to select the drawing object that is to be used as the cutting edge and then select the objects that are to be erased along that edge.

Drawing Parallel Lines and Arcs

CADD allows you to draw parallel lines, arcs or splines using previously drawn objects as a reference. This technique is often called offsetting. To draw an offset parallel line, you need to select the drawing object to be used as a reference and then specify the distance and direction of the offset. A parallel drawing object is drawn at the specified distance.

Extending Drawing Objects to an Edge

CADD allows you to extend lines to a selected drawing object. Often you need to extend lines to construct a drawing and to fix any graphical errors. To extend lines, you need to select an edge to which the lines should extend and then select the lines to be extended.

Dividing an Object into Equal Parts

CADD allows you place dividing marks on a drawing object such as a line, arc, ellipse or spline. To use this command, you need to select an object and specify how many divisions are required. This function places markers at equal distances on the drawing object.

Making Sharp and Rounded Corners

CADD allows you to make fine corners of any two lines or arcs. This technique, often called filleting, is the quickest way to join the missing corners of lines and arcs. With this function active, to make a corner all you need to do is select the lines or arcs that have missing corners. CADD automatically extends or shortens the selected objects to form a corner. You can also specify whether you want a sharp corner or a rounded corner.

Making Chamfered Corners

CADD allows you to make a chamfered corner between two lines. It works quite like the fillet command. When you enter the chamfer command, you are prompted to select the lines that are to be chamfered and enter a chamfer distance. The chamfer distance determines the size of the chamfer.

Stretching Diagrams

CADD allows you to quickly change the size of diagrams by stretching lines, arcs, splines, etc. This function is very helpful to make quick alterations to drawings. To use the stretch function, you need to select the drawing objects to be stretched and specify the distance and direction of stretching.

Enlarging or Reducing Diagrams

CADD allows you to enlarge or reduce diagrams in a convenient manner. To enlarge or reduce diagrams, you need to select the objects and enter a scale factor. The scale factor determines by how much the diagrams are to be reduced or enlarged.

Rotating the Drawings

CADD allows you to rotate selected drawing objects to a specified angle. To rotate, you need to select the drawing objects, enter a reference point (or base point) and the rotation angle. The base point acts as a pivot point around which the objects are rotated. The rotation angle determines by how much the objects will be rotated and in which direction.

Mirroring Drawings

CADD allows you to create mirror images of drawings. This capability is very useful when you want to draw something that is symmetrical on both sides. You need to draw only one half of the drawing; the rest of the drawing can be completed using the mirror function. To make a mirror image, you need to select the objects to be mirrored and indicate a mirror axis. The mirror axis is an imaginary line along which the diagram is mirrored.

Refer to CADD PRIMER for details on all the above topics.