Part 7
Module 33: Blocks
Learning Outcomes
When you have completed this module, you will be able to:
- Describe a block and explain how blocks are stored and inserted in a drawing file.
- Describe how blocks work with layers.
- Apply the BLOCK and INSERT commands.
- Explain the importance of layer 0 when blocks are created.
Blocks
A block is a collection of drawing objects that acts as one object. After defining a block, it can be inserted into the current drawing as many times as required. It can also be inserted into other drawings or shared with other users. Regardless of the number of times a block has been inserted into the drawing, it will not significantly change the size of the drawing’s database. The EXPLODE command can be used to explode a block back into its individual drawing objects.
Every drawing file has an invisible data area called the block definition table. The block definition table stores all block definitions in that drawing and contains all of the data associated with each block. It is these block definitions that the INSERT command refers to when it is used to insert a block into the drawing. The only way to remove a block from the definition table is to purge it using the PURGE command. All inserted blocks must be deleted before the block definition can be purged from the drawing. Purging is taught in Module 34.
The BLOCK command is used to create a block in the definition table. The INSERT command is used to insert a block, from the definition table, into the drawing. A block can be scaled and/or rotated when it is inserted or it can be scaled and/or rotated after it has been inserted by changing the block’s properties or by using the SCALE and ROTATE commands.
There are two methods available to edit an existing block. The first is to insert the block into the drawing, explode it, and make the necessary changes. After the changes are made, redefine the block and assign the original name. When a block is edited and redefined, it will overwrite the block definition in the block definition table and all insertions of that block will change to appear as the revised block. The second method is to use the BEDIT command. BEDIT is taught in the AutoCAD 2D Advanced book.
Blocks can also have intelligence, called attributes, attached to them. After blocks with assigned attributes are defined and inserted into a drawing, the data attached to them can be extracted.
Attributes and data extraction are taught in the AutoCAD 2D Advanced book.
It is essential to know how blocks and layers work in a drawing. When a block is inserted in a drawing, it will reside on the current layer but it is more important to know what layer the drawing objects, that were used to create the block, were drawn on. See Figure 33-1.
AutoCAD Command: BLOCK
The BLOCK command is used to create a block in the block definition table in the current drawing.
Shortcut: B
AutoCAD Command: INSERT
The INSERT command is used to insert a block into the current drawing fro