It will be far greater end result if you use more conventional methods. Do a little searching on using laser jet prints and transferring them to copper board. Then etch. Note the copper has to be very clean. use a scotch bright then clean with denatured alcohol prior to transferring the mask. If your board isn't too big Eagle will allow you to generate a circuit and layout for printing. I believe you will have poor quality of traces if you pursue 3D print a mask. It may work with traces that are .125" wide but why use a clumsy method when the procedure/process for making boards is perfected even for hobbyist use. There are also several quality board houses for boards under about 6 square inches where you can get 3 perfect boards for $30 - $50 and they use the files generated by Eagle. You can also use CAD and generate a dxf file to print as a mask. The method you propose is the wrong direction to go imo. I am an electronic technician since 1980 and have successfully built many high quality boards. Good luck to you.