How to merge common edges on a drawing ?

Hello, I've a problem with Solidworks 2014. I would like to export a DXF assembly of 2 parts and then, cut it on waterjet machine.

Actually, if I don't delete the common edges of the 2 parts, the machine goes twice on the same line and we waste time on big series. It's because Soliworks don't merge a common edge of 2 parts when I export it in DXF.

To solve this problem, I actually have to delete line after line of the common edges on the different assemblies I have to do.

I would like to know how can we delete (or merge) easily the common lines of an assembly when we export it in DXF ?

To image this problem, you can find 2 screenshots of an assembly with 2 basic pieces :

[IMG]http://i62.tinypic.com/nbc1au.jpg[/IMG]

Actually, I have to delete the common lines with this option but it takes a lot of time :

[IMG]http://i61.tinypic.com/2r4u935.jpg[/IMG]

Thank in advance,

Daniel.

SolidworksDrawings And Detailing