Making Printed Circuit Boards with the Fab Lab

Marc Boon, Feb 2008

Step 3: Creating files for driving the Roland Modela milling machine

To create the CNC files which will drive the Roland Modela milling machine, we will use Eagle's CAM Processor. The CAM Processor can create output files for a variety of plotter and printing devices. The Roland Modela is not one of them however, but we can define it ourselves, by specifying the required commands for this machine in a file called eagle.def, located in the bin folder of the Eagle installation. By adding a few line to this file, the CAM Processor now knows this machine as an output device, and can generate CNC files for it.

Replace the file eagle.def in Eagle's bin folder by this file, and restart Eagle, after saving your board and schematic.

Now, open the saved layout again, and start the CAM Processor by hitting the 4th button on the main toolbar. In the CAM Processor, load the job using the menu command File | Open.. | Job..
CAM Processor

This dialog contains the definition of a CAM job. It contains two sections: Contour Milling, and Hole Drilling. Each section specifies a device (from the modified eagle.def), an output file, some options, and the layers used.

All settings are predefined in the CAM job, and should not be modified. The only exception are the X and Y offsets in the lower left corner. Since we are milling the bottom side, the layout is mirrored (hence the checkbox labeled 'Mirror' is checked). However, mirroring the layout means that all coordinates will be mirrored around the Y-axis, translating positive X-coordinates to negative ones. We will have to offset our layout so it will be in the range of the milling machine's coordinate system. Checking the checkbox labeled 'pos. Coord' is supposed to do this, but is doesn't do it properly (it adds too much offset). So we leave this unchecked, and specify the offset manually.

For our project (and in general, for most projects), the X-offset should be equal to the width of the board, which is 1.9 inches wide in our case. Using this offset, the mirrored layout should be in the range of 0-1.9 inch. The Y-offset can be left at zero, unless we want to shift the milling region upwards a bit. This depends mostly on how the material is fixed on the milling machine. The correct offsets for our project are already filled in in the CAM file Make sure the offsets are the same for both Contour Milling and Hole Drilling sections!

To create the files, which will be send to the Roland Modela milling machine in the next step, click on the Process Job button. If it gives you a warning about layer 'Drills' not being active, click OK.
The output files will be created in the project folder, and if your board is called microtv.brd, the files are microtv.mill and microtv.drill.

Now on to Step 4: Milling and drilling the pcb.

Back to start.