why we have to take .dxf file for our simulation

hello
i want to know that why we take .dxf file of our simulation for our fabrication.
when i went to fabrication, the fabricator of antenna asked me the .dxf file so i want to know that how .dxf file helps to get the design.
when i convert my ie3d file into .dxf file i got the image of my design but i want to know how will .dxf file create the design for printing.
will i get the exact dimension of my patch like the dimension of my patch is 55mm x 87mm and so will i get the same dimension for printing also.

It's just for fabrication. The manufacturer is not interested in your design but the pattern at each specific layer of your design. In the manufacturing phase the following items are required:

* A dxf file containing the conductor pattern at each layer of your design. In the dxf file you can select any unit. (Also gerber formats are available, but dxf is readily enough).
* a specification file containing information about the design like: dielectric thicknesses at each layer, copper thicknesses, plating thickness and type, units of drawing, specifications of the vias and other information critical to your operation.
* optionally you can add gerber files of eachlayer of your design but do not forget to add gerber information into the specification file.

thanks for the explaination,

DXF is the ASCII data interchange format of the AutoCAD CAD tool. This is around for many years and has become a de-facto standard for 2D drawing data. It is quite simple and efficient, and easy to read.

Your PCB manufacturer's software does not support IE3D files, but DFX layout can be imported into many CAD/EDA systems.

When handling DXF files, make sure to tell your PCB manufacturer what units you have used. The DXF file has only numbers, but no information about the units. As taylane has described, you need a little document to specify the units and also the layer names, if they are not obvious.