Boundary Trim in AutoCAD

At one point or another, we are all faced with the tedious prospect of breaking or trimming a large number of drawing objects on different layers. There are two great commands for automating this that are hidden away in AutoCAD Map 3D. Now that AutoCAD Map 3D is included for free with AutoCAD to anyone on subscription you should take advantage of them.  You just need to download and install the AutoCAD Map 3D Toolset.

You can find the Boundary Trim and Boundary Break commands on the Tools tab of the ribbon in the Planning and Analysis workspace or by typing the commands MAPTRIM and MAPBREAK respectively.  Both commands are similar but in the post we will focus on the Boundary Trim command.

The Boundary section controls what object is used to determine which objects are trimmed and where they are trimmed. You can select an object in the drawing (a closed polyline or circle), or you can define a closed polyline by picking the vertices.

The Objects to Trim section controls what gets trimmed. You can select objects manually, by picking them on screen, or you can use powerful filtering tools to automatically select objects on certain layers.

The Trim Method section controls how the objects are trimmed, either inside or outside the trim boundary. You can also choose whether to ignore objects which have topology data and/or whether to retain data attached to objects after they are trimmed.

The Objects That Cannot be Trimmed section controls how the command treats objects like text, which cannot be trimmed. You can choose whether to ignore such objects that intersect the trim boundary, delete them, or to delete them only if their insertion points are inside (or outside) the trim boundary.

Anyone who has used AutoCAD’s standard trim command on large groups of objects can immediately see the value of this tool, particularly when you need to be selective about which objects are trimmed.  The tool is particularly useful for dividing very large datasets into individual “tiles”, such as a city-wide drawing into individual files for a map grid.