Chapter 18: Everything from Arrays to Xrefs 407

None of these options (other than opening and editing the xref) affects the xref-ed drawing itself; it continues to exist as a separate DWG file. If you need to delete or move the DWG file that the xref refers to, do it in Windows Explorer.

The fact that the xref-ed drawing is a separate file is a potential source of problems when you send your drawing to someone else; that someone else needs all the files that your drawing depends on, or it will be useless. Make sure to include xref-ed files in the package with your drawing. See Chapter 20 for a procedure.

Both AutoCAD and AutoCAD LT include an additional xref feature called exref clipping. You can clip any kind of externally referenced file or block insertion so only part of it appears in the host drawing. Use the CLIP command to trim away unwanted parts of xref drawings, DWF and DWFx files, raster images, MicroStation DGN files or PDFs. You can even clip block insertions. For more information, look up CLIP in the online help’s Command Reference section.

Blocks, Xrefs, and Drawing Organization

Blocks and xrefs are useful for organizing sets of drawings to use and update repeated elements. When to use blocks and when to use xrefs isn’t always clear, though. Applications for xrefs include

The parts of a title block that are the same on all sheets in a project

Reference elements that must appear in multiple drawings (for example, wall outlines, site topography, and column grids)

Assemblies that are repeated in one or more drawings, especially if the assemblies are likely to change together (for example, repeated framing assemblies, bathroom layouts, and modular furniture layouts)

Pasting up several drawings (for example, details or a couple of plans) onto one plot sheet

Temporarily attaching a background drawing for reference or tracing

On the other hand, blocks remain useful in simpler circumstances. Situations in which you might stick with a block are

Components that aren’t likely to change

Simple components

A simple assembly that’s used repeatedly but in only one drawing

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