EAGLE and the Milling Machine

Eagle is a great program for creating schematics and from there creating a layout of your circuit board.  You can send this board layout to a PCB manufacturer for a service charge or you can use a milling machine to etch your circuit into copper plates.  

You’re board layout, when completed will look something like this:

STEP 1:  In order for this to be millable we only need two of these layers to be visible.  Click here and change the display so that only the layers marked “bottom” and “pads” are highlighted.

Now we should be able to only see what we need to mill: the traces and solder pads.

STEP 2:  Exporting this image as a PNG usable by the milling machine fab module.  Go to file, click “export” then click “image”.  This window will pop up.  Be sure to check the “monochrome” box, this changes the image to black and white.  Then change the resolution to 500 dpi.  

STEP 3:  You’ll need another PNG file from EAGLE to cut out your board as well as to drill the holes for the solder pads.  Change the display again, this time leaving “pads” and “dimension” highlighted.  Again, export the image as monochrome and change the dpi to 500.  It will look like this:

Unfortunately this isn’t quite what we want yet.  You will have to use another image editing program.  (I’m using GIMP).  Simply use the paint bucket tool to fill in all of the black space (on the right of the thin white line) with white.  

Next:  To be sure that the milling fab module will recognize the outline of your board simply use a

brush tool (hold shift for a straight line) to make a thicker outline of the board.  This should be in black.  

STEP 4: The Fab Module

To get to the fab module type “fab” in the terminal.  Since we are using our image to mill out a circuit board click on “Roland Modela(.rml)” from” image (.png) to:

From here we will have to import your image file into the roland modela.  Click on “load.png” and select your trace file.  You will then see your image on the left side of your screen, we’ll need to create a path from here.  Click on the arrow at the top of the screen and select “mill traces (1/64)”.  This is telling the machine what size bit you will be using.  Another thing to take note on is the number underneath where it says “offsets”.  The default number is 4 which will work fine however keep in mind that this controls how many passes the milling machine will make over your image.  Selecting -1 will tell the machine to keep milling your board until the only copper left on it is where your traces are.  (Otherwise the machine only passes around your white lines however many times that have been specified, in this case 4).

STEP 5:  Setting the X,Y,Z coordinates on the milling machine.

The fab module gives you the option to set your x min and y min coordinates.  These will be the “0” point on your board.  Typically you would want to set this as near the corner of your copper sheet as you can (to save material) but you can set these points wherever, as long as your image will still fit.  Once these are set you will have to set the Z axis on the machine manually.  Do this by holding down the down arrow on the face of the machine until it just drills into the surface of your board.  Once this is set click on “make .rml”.  After you click “send it!” the machine will begin and all you have to do is wait!