"TRIM" does not work as it should

[Timber Dude]

I am trimming out existing contours from within a closed boundary. Sounds simple, right?

Except, each time I click on a contour to trim it the outcome is completely random, one of three things happen:

a.) It trims the line correctly.
b.) It completely misses the trim line and cuts out the entire contour.
c.) It fails to Trim whatsoever and I have to resort to the "BREAK" command.

This seems to be even more of an issue now than it was in previous releases. This happens in 2013, 2014 and 2015.

Another issue is that if I fence a bunch of contours, say 20 and try to trim all at once, the computer hangs and sometimes it crashes CAD.

My contours are all 2D polylines and my trim line is a LWPOLYLINE at elevation = 0m

It seems that the TRIM command does not work as it should and Autodesk really need to fix this as it has only gotten worse over time.

See the attached image for what I mean.

trim.jpg

[Timber Dude]

So... I ran "CONVERTPOLY" and changed them all from "2D Polylines" to simple lightweight "Polylines".

The contours are now behaving themselves and acting consistently in AutoCAD 2014. Still having issues trimming multiple contours at once in 2015 with the machine crapping out and crashing everytime.

[Tom Beauford]

It's probably the linetype. Using trim with a dashed line that doesn't graphicly touch the other line because of a gap causes this. You could change every layer to continuous linetype to trim, then use Layer Previous to get the linetypes back afterwards.