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How to delete an empty union (Altium 17.1)


I am creating PCB unions to make board revisions to a multi-channel design. I'd originally done the initial layout with rooms, but once the identical sections were copied over I deleted the rooms since there were some components that had to encroach on rooms to make the design fit.  Now I've got the 2nd rev in progress and found that I can group what was originally in the rooms into PCB unions to help with positioning of the changes.

I've somehow managed to create an empty union. I can click on it (nothing is highlighted/masked since there's nothing in it) but I cannot delete it. Normally you right click the union and break (all) the components out of it, but that option isn't available since there's nothing in the union.

Has anyone managed to do this and figured out how to get out of it?

How do you know the union still exists? Since you cant normally click on a union, only on objects in one.

Few ideas
- Can you draw box around it to highlight it and hit DEL key?
- Try going to Board Planning Mode (press 1) and see if you cant select/delete it any better when in that mode.

I see the empty union in the PCB list window, under "Unions". It has zero primitives in it.

There's nothing to select in the PCB window itself, it only seems to exist in the PCB window.

Yep, I've seen that too. Don't know of any way to delete them.  Unions seem to be lower-class objects, in that they can't be selected or edited or queried (aside from InUnion(number) only).

Possibly there are more hooks via scripting interface.  If not, I guess the only solution would be to edit the PcbDoc directly -- reverse-engineer the format, find where unions are enumerated, delete the empty ones, then repack the file so all headers and offsets are still valid.

Possibly we can convince Altium to address it as a bug, if we find a way to crash it.  Can we produce enough empty unions to cause faulty behavior (maybe corrupting other unions, or making a ridiculously oversized file, or outright crashing the program)?


Hello guys,

I was looking for the exact same feature and finally found that there is now a dedicated context menu entry "Delete selected Unions" in the PCB panel. Screen capture attached.

Hope this could help others.


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