Mirroring PCB

 It looks like the method I will need to use is to export the layers individually to a .plt file and import them back in on the appropriate layer.

I am trying to export the clines referenced to the origin of the board.  How do I set the origin when exporting the .plt file?

The easiest way is to create some "dummy" layers in the cross section and then use the Edit - Change command and zcopy to move the clines and shapes to the required layer. Then when you've finished remove the "dummy" layers. 

Hi,

If you are looking to mirror (flip) select traces you can use the RMB Menu "Mirror Geometry" via the Move or Copy command then you can change the traces to the new layer.

If you are looking to flip the entire board or a large circuit you can generate a Place Replica to perform this task.  Once you generate a Place Replica of the components, clines and vias it will become a group that can be moved as one element, mirrored(flipped) to the opposite side of the board.  This effectively mirrors the entire design with top side traces being moved to the bottom side, etc.  Once it is flipped you can Disband the group so they are no longer related.   Let me know If you haven't used Place Replicate before I can quickly go thru the basics.

Hope this helps,
Mike Catrambone

I am not aquainted with the RMB menu.  The only mirror command I have been able to find is under the  Edit menu and it only affects Groups, Symbols, and Text.  I tried to group my symbols, vias, and clines, but when I mirrored the group, the clines did not mirror.

 I have not had any experience with Place Replica and again I have never seen it in my menus.  I am running Allegro PCB designer and I am not sure I have all the features you are talking about.

If you start the Move Command (Edit > Move) then window a couple of Clines, select an origin point to move the Clines and once they are on your cursor click on the Right Mouse Button (RMB) to get access to Mirror Geometry.  This will allow you to mirror the elements while they are attached to your cursor then place them back down.  The same "Mirror Geometry" RMB Menu option is available with the Copy command as well.  This only works for Cline, Vias and Shapes and if you select a component the "Mirror Geometry" option will be greyed out on the Right Mouse Button Menu.

Which Version of Allegro are you using?