I’ve been spending a lot of time on CNC lately.  Quite a while ago I wrote about mounting my Olimex MT-128 circuit board in a plastic box to make it easy to take with me places.  That was a good idea, and it certainly kept the cat away from my projects.  Unfortunately, it also made it quite difficult for me to work on a project.  The problem was in getting to the back of the circuit board to plug in programming headers, connect to pins, etc.  For some reason it took a while for me to realize the neatest, cleanest solution: mount the experiment board to the top of the pencil box.  Genius!

Not so fast, though.  I tried that once before and it was mostly a failure.  Trying to hack up a flimsy plastic box with any precision is no easy task.  This time, though, I was armed with a lot of recent CNC experience.  I opened up TurboCAD and drew up the dimensions (or so I thought) of the faceplate.  Before machining, I printed it out.  It’s a good thing, too.  My dimensions were way off.  Have I mentioned that I can’t measure very well?

Fortunately Olimex has a drawing with dimensions for the board on their website.  Using those, I was able to create a perfect drawing. 

Next, I exported to a DXF and pulled the file into CamBam to define cutter path and create the CNC G-Code.

When I loaded the code onto my mill and cut the shape, the results were…terrible!  I didn’t support the plastic from the bottom, and it flexed so much that the dimensions were all over the place.  This evening I cut a 2x4 to fit under the box lid.  To mount the board to the mill I recessed two holes in the board, then I clamped the pencil box lid from the top.

I think the results the second time around speak for themselves (despite some fisheye from the camera).