You can convert a complex entity, such as a block or polyline, from a single entity into its component parts. Exploding a polyline, rectangle, donut, polygon, dimension,or leader reduces it to a collection of individual line and arc entities that you can then modify individually. Blocks are converted to the individual entities, possibly including other, nested blocks that composed the original entity.
With the following exceptions, exploding an entity usually has no visible effect on a drawing:
If the original polyline had a width, the width information is lost when you explode it. The resulting lines and arcs follow the centerline of the original polyline. If you explode a donut, its width becomes 0.
If you explode a block containing attributes, the attributes are lost, but the original attribute definitions are retained. The colors and linetypes of objects in exploded block references can be modified individually.
Colors, linetypes, lineweights, and print styles assigned BYBLOCK may be different after exploding an entity, because they will adopt the default color, linetype, lineweight, and print style until inserted into another block.
You can explode polylines into simple line segments and arc segments, which neglects the width of a polyline. The exploded lines and arcs are placed along to the center line of the polyline. To be taken as a polyline object, the donut would be changed into two arcs that form a circle ( with width as 0) after exploding.
Explode Dimensions and Hatches
You can explode a dimension or a hatch into individual objects (such as lines, texts, points and 2D solids). all associativity is lost after exploding.
Explode Block References
You can explode a block reference into individual objects. if a block to be exploded contains attributes, the attribute values are lost and leaving attribute definition. If you explode a block that contains polyline objects, you have to explode the polyline separately.
To explode a block
Choose Modify > Explode.
Select the block.
Command line EXPLOD
Explode External References
You can not explode external references or the dependent blocks as they are linked or attached to another drawing.
EXPLODE: Explodes a compound object composed by multiple objects (blocks, polylines .etc) into single objects
System Variables Reference
EXPLMODE: Controls whether the EXPLODE command supports nonuniformly scaled (NUS) blocks