Drawing a PCB by exact dimensions using EAGLE PCB isn’t quite the easy thing. An easier approach would be to draw it in AutoCAD and then import.
Importing is quite easy. This is how it goes. This is my simple pcb 😀
Now what you need is to save the drawing to DXF format by going to Save As and chose AutoCAD 2004 DXF form the Files of type drop down menu. Name your file and save it.
Now you need to convert this file to something that EAGLE would understand – a script. For this to work I use a simple DXF so SCR converter by http://www.micromagicsystems.com/
Here is the app:
Load the file and hit convert. You need to provide destination for both input and output file.
Now you go to EAGLE PCB and select File -> Script. Find the SCR file and open it. Now you should see the exact same PCB form the AutoCAD drawing.
However you will need to place holes and drills. Those you see now are drawn on the Dimensions layer AND WILL NOT FORM ANY ACTUAL DRILLS. Here is a trick that helps me dealing with this.
It is wise to put some sort of a mark for the center of the holes when drawing the PCB in AutoCAD. A small cross would do just fine. After importing the drawing to EAGLE those crosses will be used as a markers to show the exact place of the holes and drills. This is how I do it:
After the import you need to zoom in to the center. Turn your grid on (I use dots) and carefully align the center of the hole and the marker. Take note that after the import the grid is set to Finest(which is 1 mil) You might need to use the Change command to make the lines 0 mils in width. It’s easier to see the grid this way. Now use the move command to get the hole or drill. The holes are usually placed on the schematic so they have names like H1, H2 .. etc. To grab the hole just type its name in the command line.
It is a tricky job but with some practice you will get used to it 🙂 When you are finished aligning the holes you can delete the markers. Now you change your grid back to normal.