PCB Milling (Take One)

Here's a picture of the mill. The "bed" (table thing that holds the board) moves fore/aft, while the motor and tool move left/right and up/down. The mill can cut in three dimensions by precisely controlling these three directions in concert.

Keep in mind that the bed is only about 6"x6". This is precision machinery.

It took about 40 minutes to do the first side and drill some holes. It looks pretty ragged when it comes out, but a little rub with an abrasive pad makes it look shiny and official. 

You can see above where the outline is incomplete. I should have saved that completely for the end, as well as the holes, because the mill likes to do all the thin parts before digging into the the substrate.

And now the Big Lesson:
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The board must be mounted very consistently or else the mill can't do its job correctly. This is especially true for double-sided boards, because everything needs to line up on both sides. For this mill, you place the board against a little guide in the close-left corner for one side, then flip the board and place it against the guide in the close-Right corner. Now it is registering its movements according to the same "landmark" on the board (otherwise this would be a huge ordeal to measure out). (As you may notice in the pics, this mill uses one single piece with a corner at each side)

Anyhow, the board must not have been pressed in the same for both corners, because the holes it cut don't line up. Curiously, the mill had trouble getting through the copper in a few areas on one side, like maybe the board had an ever so slight dip there. Maybe I should try to change the thickness setting so the cut goes a slightly deeper and the tolerance isn't so critical. Obviously I don't want it to cut through the majority of the board, but a teeny bit is okay.

Above shows the computer program's display, with super thin blue lines showing the route the bit (the gray cylinder at left) will travel. I have no idea how it figures this out, but I will say that it just nibbles here and there, poking around, and only occasionally does long stretches like I expected. The computer animation is synchronized with the actual mill, and it is super duper mesmerizing to watch. The only thing I can figure about the nibbling is maybe that it randomizes the puncturing of the copper so it doesn't start peeling. In any case, below shows some detail of the ragged edges before clean up. 

In this picture above, you can also see how the holes are almost a full width off. On the left side here, I think the leftover circles are where the [incorrect] hole on the first side allowed the copper to flex under the bit. However, I don't think the holes were the only issue, because (as shown below), the lines didn't cut completely in other places too. As said above, I think a depth adjustment will improve the results.

Above right is a closeup of the 1/32" bit. That is my index finger. 1/32" is small. 

Thank you Cynthia for the macro lens!!

Well, Folks, that's it for now. I'll let you know how it goes with try two...