Hi If you ever get a chance to visit a PCB fab it’s an interesting sort of process. No two of them are quite the same. The gear they have does impact what they can or can’t do. Every one I have ever visited has done routing on the boards. That may be because it is a very common requirement on industrial boards. Essentially they just swap out he drill bit for a routing bit and go with it. It’s not quite that simple, but almost. The big reason you don’t see it done on the low end boards is that it takes time. The machine isn’t a cheap item so in this case time is money. It’s the same reason a “real” fab will hit you with a charge for the number of holes you want on the board. Same basic issue - time on the machine.
Bob > On Apr 28, 2017, at 2:31 PM, Bob Stewart <b...@evoria.net> wrote: > > Hi Bob, > It may be because the process of cutting the boards apart is not part of the > board milling process. Yes, cutting holes in boards for through-hole parts > is part of the business - round holes. The fab house for OSHPark won't make > oval holes. They won't overlap two holes, either, nor make square notches. > This is only a guess, but I'd say that this is because they use actual drill > bits to make those holes, rather than a laser. Drill bits are expensive, and > it takes a lot of time to change a drill bit when you've got hundreds of > boards to mill. It's not something I would want to do, either, without a > serious penalty for the customer for a broken bit due to odd shaped holes and > missed deadlines. > > And OSHPark seems to use different fab houses for the small runs vs the large > (10+) runs. With the small runs, the boards are connected to each other by > small tabs. Often small boards arrive still tabbed together. I don't know > whether they route the distance between these tabs, or use a laser. On the > larger runs, there are no tabs, and the board edges are smooth, as if they > were cut apart in one single operation not part of the milling process. > > NB, I don't work for a fab house, nor have I ever toured one. > > Bob > > > > From: Bob kb8tq <kb...@n1k.org> > To: Discussion of precise time and frequency measurement <time-nuts@febo.com> > Sent: Friday, April 28, 2017 1:06 PM > Subject: Re: [time-nuts] TAPR Oncore M12+ kit > > Hi > > If you go with the PCB approach, the nice thing is getting stuff like > the slot for the D connector done at the PCB fab. That way you > have something that drops right in and works. The downside is that > not every pcb house is happy doing that sort of “CNC work”. I > have absolutely no idea why. They all have to run some sort of gear > to cut the boards apart. Cutting slots or weird holes with it is pretty > trivial. > > Bob > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.