I have a drawing file that was created from another drawing that was about 1.5M but the actual used data was very small. After much frustration from not being able to purge all unused items (ran purge many times, used laydel on unwanted layers, ran audit, recover, etc.), I decided the best method was to copy all the desired entities into a new drawing.
With immediate relief, the drawing was then reduced to 62kb (not much data).
I then reattached 2 external references (3.6M & 1.8M) that increased the file size back to about 1.4M. Even after detaching these external references (and purging, etc), the file size is remains a 1.4M when it only has small amounts of desired data.
Why does this happen and are there any solutions?
My overall issue is that I have a large group of drawings that get referenced to make a complete drawing. This becomes very large drawing file that is difficult to work with. I am trying to reduced all file sizes to 'clean up' the drawings a bit.
When you bring in an XREF, AutoCAD needs to be able to process the contents of that file. Since files may contain a variety of custom objects and/or data in order to be shown properly, certain things end up being copied from the XREF into the host drawing. These include, but are not limited to, annotation scales, registered application names, and third-party data (depending on availability and function of object enablers).
Not every "object" in AutoCAD is a drawing entity - many are data-only and have no corresponding entity in the drawing proper. With no visible entity its easy for users to forget about or not even be aware of this extra data, allowing it to follow from drawing to drawing as users insert, XREF, and copy-paste their way through their jobs. This is where WBLOCK can hold an advantage - if you just WBLOCK your non-intelligent items to a clean file the abandoned-in-place data will not follow. At least, provided its not attached directly to the objects, but thats another issue...