By Dennis Collin
A common question I receive whilst training AutoCAD is ‘What is the difference between a block and a group?’ or ‘When should I use a group over a block?’ The two functions at first glance are similar, but each have a slightly different purpose. Blocks have been within AutoCAD since the earliest versions. Blocks contain objects that can only be manipulated as a collection of objects. Blocks are used for symbol elements, which are repeated throughout a drawing and can be used to represent such features as furniture or equipment within a building, or components or subcomponents within a wider assembly drawing. A block is defined outside of a file, either as a separate drawing or the block editor. Once inserted or applied to the main drawing any changes to the block will be applied to all blocks of the same name in the drawing.
Groups are a slightly newer feature and were introduced to AutoCAD to provide more flexibility for repeated selection operations. A group is an ideally logically named saved selection set which is defined within the drawing. Elements within this set can be selected individually or together as needed. A typical example of a group might be a collection of elements like a typical bathroom or kitchen layout. Groups are intended to be more ad-hoc in nature and are designed to be modified and ungroup should the situation require it. Whereas a block definition is perhaps less likely to be changed as frequently and are more permanent in style than a group.
Groups will be unique to each drawing, whereas Blocks can be transferred to other drawings using such interfaces like the Blocks Palette, Designcentre or Tool Palettes which in turn become libraries of commonly used components. A group arrangement will be more flexible in nature and can be maintained or ungrouped as circumstances require. Should a group need to be shared to other drawings, it would need to be converted to a block and then shared via a suitable ‘library’ environment or copy and pasted between source and target drawings. Groups themselves cannot be transferred between drawings. The elements will be copied but the grouping structure itself is lost.
Personally speaking I tend to favour the use of blocks over groups as they tend to be more reusable, and should I wish to break them down, blocks can be easily exploded as individual elements. This makes the distinction between the two functions very fine. However, for users who need to repeatedly select elements, add and remove elements to that selection easily without having to work in a structured way like a block find using Groups a more useful workflow.
One of the great benefits of AutoCAD’s longevity is that the software is very flexible in how it can be used and suits different workflows and situations to produce technical documentation in the most efficient way for each organisation.