proper way to draw cutouts

[djacobow]

I'm designing a circular board. It's easy enough to make the board outline a circle and send that to a prototyping shop, but since they charge you for the enclosing square, I figured I'd take advantage of that space for some small boards.

Fair enough, except that now I need to carefully draw cutouts so that my boards are all mostly separate from each other, but not entirely, so that the whole thing stays together until I cut it at home.

The OSH Park design rules specify that cutouts are OK, but that the minimum cutout is 100 mil and that the corners will be round. I presume this means that the router bit is 100mil.

Now, I'm using diptrace, and no matter what width I specify for a board cutout, it always draws the same width line, which is confusing, and leads me to believe that when I draw a cutout I am specify the edge of the cutout area, not the center of the bit, if that makes any sense.

For example, if I want a channel of 100 mil, I don't just draw a line in "board cutout" set to width=100mil, but I draw a box, 100 mil wide. Is that correct?

I've looked at my gerbers in a viewer and the lines drawn are still very thin, so again, that seems to confirm my suspicion that I am specifying the shape of the cutout area, not the placement of tool; the board people will take care of that.

Is that so?

Another sub-question: If I want sub-boards routed out entirely, can I just specify a routed shape that cuts out the whole board, and they'll just send me all the "pieces" or so I need to leave connecting tabs to hold everything together? And assuming the latter, how thick/strong must those be?

Regards,
Dave J

[djacobow]

Nobody, eh?

Well, my plan to utilize this space has been thwarted for now by the pin limitation in DipTrace which I am not prepared to pay to remove.

:-(

[Wilksey]

I can't help with the question as I don't use DT much, but you can get a non profit license key from Novarm that will expand your pin limit to 1000 I believe for free, not sure if that would help you with the pin limit?

[kizzap]

To draw "cutouts" as you describe, all you have to do is draw them into the board outline layer. I believe off hand that the router bit they use is 2mm, but I am not 100% sure on that.

[tekdemo]

Howdy! Dan from OSH Park here. Figured I'd drop in and answer your questions.

The OSH Park design rules specify that cutouts are OK, but that the minimum cutout is 100 mil and that the corners will be round. I presume this means that the router bit is 100mil.

Correct!

Now, I'm using diptrace, and no matter what width I specify for a board cutout, it always draws the same width line, which is confusing, and leads me to believe that when I draw a cutout I am specify the edge of the cutout area, not the center of the bit, if that makes any sense.

For example, if I want a channel of 100 mil, I don't just draw a line in "board cutout" set to width=100mil, but I draw a box, 100 mil wide. Is that correct?

I've looked at my gerbers in a viewer and the lines drawn are still very thin, so again, that seems to confirm my suspicion that I am specifying the shape of the cutout area, not the placement of tool; the board people will take care of that.

Is that so?

Yup. You're detailing where the edge of the board should be, and the fab will actually specify the tooling path. This is done for a couple reasons. One of which is because the fab needs to re-do the routing path anyway, since they have to account for the support tabs. Another major reason is because sometimes the fab will sometimes opt to use a 68 mil routing tool, which would make all the user-entered routing paths incorrect.

Another sub-question: If I want sub-boards routed out entirely, can I just specify a routed shape that cuts out the whole board, and they'll just send me all the "pieces" or so I need to leave connecting tabs to hold everything together? And assuming the latter, how thick/strong must those be?

As hinted above, the fab will add in the support tabs. All you need to do for us is draw all the edges for the various boards, and we'll take care of the rest. You can of course draw in your own tabs, but it's typically not worth doing unless you have specific requirements about placement, or if you want copper interconnects.
We  try to leave panelized designs intact, so you'd most likely get them attached together.

[djacobow]

Dan, thank you very much. All my questions answered in full! That's service!!! :-)

Regards,
Dave J

Howdy! Dan from OSH Park here. Figured I'd drop in and answer your questions.

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