Homebrew PCBs

Alan,
     Mechanical Etching bits can only move  .0004 to .0006" per
revolution of the spindle. This limits the machines that can make
circuit boards. I always get a laugh when I see an adapter to hold
a Dremel in a Bridgeport. A ton of power but not enough speed to 
engrave or mill circuit boards. PCBMills run 15,000 to 30,000 rpms.
     If you search the internet you will see a few test boards that 
are milled. I have only seen a few real boards that are milled. There 
is alot of talk about using dental bits. I use a bit that was 
designed for milling circuit boards. The best you can hope for is 800 
inches of copper per bit. People ask me about milling 12" by 12" 
boards all the time. Good luck with that idea. Even a few traces on
a 12" by 12" board will add up to 800 inches very quickly. A 12" 
trace is really 24" long.

                                        John 


--- In Homebrew_PCBs@y..., Alan Marconett KM6VV <KM6VV@a...> wrote:
> Hi John, 
> 
> Yes, I can see that you've spent a lot of time and energy designing 
your
> boards and mills.  And writing manuals and preparing plans for 
projects
> also takes considerable effort!  Hopefully you will get to a point 
where
> you CAN make a reasonable profit.  
> 
> If your customers want something (and will pay for it), then you 
should
> have a market.  I do see a lot more boards and other CNC products
> available then when I started.  
> 
> I have several unipolar drivers, don't get me wrong.  And for the
> experimenter on a tight budget, they DO offer an advantage over the 
more
> costly "modules".  You're correct, high rapid's and feeds are not 
needed
> by a hobbyist!  Plus, unipolar drivers have the advantage that you 
are
> less likely to "fry" them while you're learning!  And it's FUN to 
see
> what you can do with as little as possible!  Anyone can lay out $5K 
or
> whatever and buy a turnkey package.  But to build and get it running
> yourself, that's another story.
> 
> I currently have my Sherline set up for CNC milling (my PCB router 
is
> not finished yet), so I think your board is a little too big for 
it. 
> I'll have to consider this a "paper" exercise, until such time as I 
can
> cut the board.  As I've said, I'm more interested in technique and 
some
> "real" examples to compare to my Gerber/Gcode efforts.  Knowing what
> you've done on your board would help me to get my process (and 
program)
> tested out.  Thanks for the kind offer!
> 
> Alan  KM6VV
> 
> 
> crankorgan wrote:
> > 
> > Hi Alan,
> >         I sell 4 axis unipolar controllers. They are heavy duty. I
> > kept getting asked to make a Bipolar board. So I added a L298 to 
my
> > design. A simple cheap board for experimentors. What it comes 
down to
> > is they save $10 buying my board while I loose hundreds designing 
and
> > debugging it. What I find is people are unable to find anything on
> > the internet. Maybe they use the wrong search engine. I was told 
when
> > people ask for something, make it avalible. I should have bought a
> > batch of Dan's boards and resold them! Now that a Business!
> >       There are several people besides myself who sell unipolar
> > driver boards. A first mill only needs 12" per minute. A Dremel 
can
> > only handle 8" per minute with a 1/8" bit. Going 20" per minute 
with
> > a bed that is only 6" X 6" is insane for a beginner. Cheap 
unipolar
> > drivers can run cheap motors at 20" per minute. I myself only 
work at
> > 6" per minute. But because my GCodes are very efficent, 
effectively I
> > am milling faster.
> >        Mill a Tit 4 Tat and I will send you the instruction 
booklet
> > via Email. There is a photo of the board under How to Mill Circuit
> > boards.
> > 
> >                                     John