Les, dude, thanks.
Having been a machinist once on Bridgeport milling machines, I recognized that everything you were saying was spot on.
I can save a serious chunk of dough making the 3D ... maybe even 4D rig myself, with surplus steppers and my own circuit boards from scratch...
and spend the money where it really matters: the spindle itself. Something ridiculously fast with close to zilch run-out.
Thanks for all the links and tips; this is soooo the way to go, I'm never looking back at etching again...just gonna use the protoboards that match up to breadboards until I get the PCB milling rig done, and then convert straight to milling. (routing).
My God, I can't even imagine .005 run-out! They actually make spindles that bad?
When I get my steppers working I'll post the circuits and rig here...with new PCB's made on my PCB mill, that is ;)
Just to theorize a little....it did just recently occur to me that this could also be done by using, instead of a rotating spindle with a V bit and drills, a very fine, very high speed/pressure jet of abrasive...either air based or water based. I know such things are made....I remember reading of one that had a diamond head, because the jet of water that came out was under such high pressure and at such an insane speed it cut through inch steel plate like it was butter...soft butter.
Now, THAT would be a fast method. In fact, the table would have to move FAST to keep the jet from just boring right through....heh heh heh...but it could be done, no doubt about it. I'll have to google if there are any micro-jet rigs/heads for such a thing. And incredibly fine abrasive.
Best, Charlie
--- In Homebrew_PCBs@yahoogroups.com, Leslie Newell <les.newell@...> wrote:
>
> Hi Charlie,
> > Yes, there are two worries that I mainly have about using a 3D router:
> >
> > burring and minimum trace width/clearance.
> >
>
> With the right equipment you can get quite fine traces. I have seen
> boards made this way with two tracks fitting between 0.1" pitch pads. To
> achieve that sort of resolution you need a very accurate spindle as even
> 0.005" out of center can make a big difference. If your spindle is not
> perfectly concentric the cut width will increase and you often get
> problems with burring. If you get burring, stop cutting and rotate the
> cutter in it's collet by 45 degrees and try again. Repeat until you find
> the 'sweet spot'. A worn cutter will of course also cause burring.
>
> > I'm pretty sure surface mount would be "out"...but maybe not.
> >
>
> Fine pitch such as QFP packages is out but other surface mount is fine.
>
> > On the other hand, once it's setup and debugged, it's repeatable, fast
>
> Not as fast as you would think. Routing is slow but you can just leave
> the machine to get on with it. It is also generally quite noisy due to
> the high spindle speeds (15,000RPM to 100,000RPM, depending on how deep
> your pockets are).
>
> > , and the automated hole drilling is not to be sneezed at; I find the hole drilling part by far the biggest hassle and would love to have it done automatically....I suppose
> >
>
> Yes, drilling is far faster and more accurate than hand drilling. Before
> I went over to routing boards I used to photo etch then CNC drill.
> Aligning the board was always a PITA.
>
> > However, if the hole diameters were standardized to one size (in some circuits this is doable, even if it isn't optimal), one bit could do it all: routing and drilling...all in one multi-stepped set of passes. That would be pretty cool. It would have to be a carbide or even diamond bit, at a very high speed, maybe even with water cooling, but I'm sure it's achievable.
> >
> > And, now that I think about it more, actually larger holes would, of course, be achievable: just program it in to to mill the hole out larger.
>
> Don't go there. Thin routers break VERY easily. In my experience
> anything below 1.5mm (1/16") is asking for trouble. Cut the tracks with
> a V cutter like these
> <http://cgi.ebay.co.uk/5-x-45-Carbide-PCB-Engraving-Bits-CNC-Router-Tool-T14-/250522253434>
> then drill with normal carbide drills. You can get plastic collars that
> fit on drill shanks to set the depth. Once you have the machine and
> collars set up you can change cutters quite quickly because they always
> fit in the collet at a fixed depth.
>
> You don't need any form of coolant. It just makes a mess. Use decent
> vacuum extraction to keep the abrasive dust out of your machine and out
> of your lungs. As far as hold-down is concerned, vacuum works quite well
> if the vacuum is strong enough. A vacuum cleaner is definitely NOT
> strong enough. When drilling and routing parts out you need to cut all
> the way through plus a bit so you need a backing sheet of some sort. For
> vacuum this sheet needs to be porous. 6mm (1/4") MDF works and is pretty
> cheap. I just use double sided adhesive tape to hold the boards down. It
> is quick and easy. You need to experiment with the tape. White 'carpet'
> tape sticks well but is a pain to remove and tends to clog cutters.
> Transparent tapes generally work quite well but can be difficult to find.
>
> For double sided boards, drill a couple of locating holes in your blank
> board and use them to locate the board on pegs on your table. These
> precisely locate the board when you flip it over.
>
> One stumbling block is the software to generate tool paths. It can be
> quite expensive. The free offerings are generally rather quirky. I quite
> like Visolate <http://sourceforge.net/projects/visolate/> though it
> takes some trial and error to get it working correctly. Instead of
> slavishly following the track outlines it calculates the minimum cut
> length to achieve the desired connectivity. The resultant tracks look
> odd but it works well. Cutting time and cutter wear is considerably less
> than most other methods. There are some pics here
> <http://www.mit.edu/~vona/Visolate/Visolate-info.html>. Visolate won't
> do the drilling.
>
> I use SheetCam <www.sheetcam.com> for drilling. Actually what I do is
> generate the tracks in Visolate them import the tracks and drill files
> into SheetCam. I can then lay them out as I want them before cutting.
>
> Les
>