to run first (Figure 12).
Start in the Generation Options tab by changing the
parameters to match the board thickness (milling depth),
clearance minimums and maximums (isolation default/
maximum), and the etching tool size (Figure 13).
Remember to un-check the "Generate top outlines/drills"
as we are doing a single-sided PCB with traces on
Next up is the Machine tab. You can modify the
parameters to match your CNC machine including Spin
Up Time and Drill Dwell (in seconds), drill depth (I used
0.070" for 0.064" copper clad), and tool change position
in x, y, and z (the CNC will move to this position for a tool
change). The GCODE Style tab allows you to select the
appropriate version; in our environment, we chose EMC
for EMC2 under Linux.
After making these changes, choose "Accept and
make my board." You should see a pop-up asking to run
Windows’ viewer (Figure 14). After accepting this, there
should be a series of drawings, each followed by a "close
this window" dialog box (Figure 15).
When done, the PCB-GCODE plug-in will generate
etch, drill, and mill files, typically located in the "My
Documents/Eagle" folder on your machine. The "etch" file
contains the mechanical etching of traces and pads; the
"drill" file contains the holes to be drilled; and the "mill"
file contains the perimeter cut information for the
HERE THERE BE PENGUINS!
At this point in our environment, we simply copy the
".ngc" files to a "thumb drive" and take that over to the
Linux machine we have connected to the Fireball v90.
Once the files are copied, a few small changes need to be
made before we start. First, the drill file has to be edited
for tool changes. Look for lines that start with M06 and
put everything from the semi-colon to the end of the line
in parentheses. For example, this: "M06 T01 ; 0.0320"
should become this: "M06 T01 (; 0.0320)" This change will
make EMC2 stop and ask for a tool change.
Setting the depth for PCB etching may be a bit
tedious. Typically, you start with the z axis "zeroed" on the
surface of the copper clad (this can be done by eye or by
placing a small piece of paper under the bit and then
owering the z axis until the paper is pinned. Then, back
A THANK YOU ... OR TWO ... OR MORE ...
I want to thank Paul Atkinson for all his help in preparing
the material for this article and his wife Dolly for letting
Paul come out and play (thanks for the pizza too!). Also,
special thanks go out to Len Shelton of PROBOTIX for
his unflagging dedication to the vision of home-CNC and
his top-shelf customer support. Plus a quick shout-out to
the guys at Precise Bits — you really know your stuff!
■ FIGURE 11. Type "RUN" in the command line on
EAGLE to start PCB-GCODE.
■ FIGURE 12.
■ FIGURE 13.
Options tab from
■ FIGURE 14. PCB-GCODE prompts you to open the
Windows Viewer to see the results.
■ FIGURE 15. The trace isolation "etch" path generated
July 2009 63