Hi Alan,
I only buy scrap PVC 1/4" thick grey. There is a guy on
Ebay who sells several 18" X 18" pieces for around $10 plus
shipping. I have picked up some for even less. You can drill it,
tap it, sand it, and glue it. Hobby stores sell it in thinner
sizes. Robotic people use it. I just mount the PVC to my Bed
which is also PVC. I used to mill my fixtures flat. Now my
designs are more accurate.
Some PCB have foil that is thinner and some have foil
that is softer. The surplus I buy is tough as nails. Not one
trace has ever lifted or torn.
The 60 degree bit will allow you to have an uneven Bed
or board. Some areas will be milled wider, but they will still
be milled! Since my boards come from the same place they are
the same thickness and size. This allows me to come off the
home positions to mill the board.
I consider milling circuit boards a great way to check
a design before you send the boards out to be made. I use the
method to make the boards I sell. I am able to sell a board for
the same price the customer could make it for. I also make a small
profit. The biggest cost is the bit! $7 each and in my case that
is only one board.
I see you asked about wear on the other group. I use a
LFKF-T-Tech type bit. Micro-grain carbide. You get about 600 good
inches and an other 200 inches of so so milling. I have my bit
make starter holes at the end of the run in each pad. That takes the
bit its last mile. The expensive machines spin the bit much faster.
This helps the bit last longer. Several people who use the real
machine told me I am doing ok! Not bad for a $125 machine.
John
--- In Homebrew_PCBs@y..., Alan Marconett KM6VV <KM6VV@a...> wrote:
> Hi John,
>
> Where do you get the PVC, other then a "plastics" store? Anything I
> missed? I think there is a TAP plastics in San Jose, CA.
>
> The 'L' picks up two edges of the PCB? Do you flycut the PVC flat
> first? should true it up.
>
> I have a 60 degree engraving bit that was recommended to me.
>
> Yeah, getting two traces between pads is a little hard to achieve!
I'll
> settle for a single trace. I've seen their sample boards, really
nice.
>
> Are you saying that they use thinner copper or a special board for
> mechanical etching? I hadn't heard that.
>
> Alan KM6VV
>
> crankorgan wrote:
> >
> > Hi Alan,
> > I mount a 8" X 8" piece of 1/4" PVC to my bed
> > using four flat head 10-32 bolts. I run the machine with
> > an old Mechanical Etching bit in it. I cut a fine "L" in
> > the plastic. In the "L" I drill and tap 2-56 bolt holes.
> > I then place a PCB under the bolt heads. This helps me
> > locate where the other screws go.
> > The board is held down on all sides with just the
> > bolt heads. If you use a 60 degree Mechanical Etching bit
> > variations in copper and board will not be a problem. This
> > is if the board is cuped up! The single sided ones I buy
> > are.
> > My machine will do a trace between a pad. Two traces
> > between a pad!!! No way! I have seen the sample boards on
> > those site. Show me the boards made by regular people using
> > their machine. No burrs either, just perfect traces.
> > The boards I use have very thick copper. If I get
> > the money, I will try some PCB made for Mechanical Etching.
> >
> > John
> >
> > --- In Homebrew_PCBs@y..., Alan Marconett KM6VV <KM6VV@a...>
wrote:
> > > Hi John,
> > >
> > > Good tips! When you bolt your boards down, how much deviation
is
> > left?
> > > I just looked at LPKF (again, for the 1000th time), and they are
> > VERY
> > > precise! TWO traces between pads. And I'm thinking that if the
> > depth
> > > is controlled more closely, bit life will be improved.
> > >
> > > Alan KM6VV
> > >
> > >
> > > crankorgan wrote:
> > > >
> > > > Hi Alan,
> > > > I see that! I use the heads of 2-56 bolts to hold
> > > > my boards down. The ones I buy are cuped foil side up. They
> > > > are 4" X 6". The bolts go into a piece of 1/4" PVC. I find
> > > > holding the board by the edge-the best method so far. Since
> > > > all my boards are 4" X 6" I only have to take two bolts out
> > > > and the board slides out the end. The bolts pull the board
> > > > down flat. When I do smaller boards, I have other rows of
> > > > taped holes in the PVC. The Tit4Tat board was 1/2 of the
> > > > 4" X 6" board. I would make two at once. I used to make 4
> > > > 1 axis boards out of one 4" X 6". Tape is fine for doing
> > > > a flat pcb, but most surplus boards come warped.
> > > > How would I fix a warped board when making a double
> > > > sided board? Simple, use one or two bolts in the middle of the
> > blank.
> > > > They then become mounting holes.
> > > >
> > > > John
> > > >
> > > > --- In Homebrew_PCBs@y..., Alan Marconett KM6VV <KM6VV@a...>
> > wrote:
> > > > > Hi Listies,
> > > > >
> > > > > Some activity on the CCED list about LPKF and holding PCB's
> > down to
> > > > mill
> > > > > them. Anyone here have the LPKF system?
> > > > >
> > > > >
> > http://www.lpkfusa.com/products/product/rapidpcbpro/index.htm
> > > > >
> > > > > I'd like to get a closer view of the Z height "tracking
donut"
> > on
> > > > this
> > > > > machine. And, I'm in the process of downloading a demo of
their
> > > > > program.
> > > > >
> > > > > Alan KM6VV
> > > > > P.S. I'm also looking at a low-cost Gerber to Gcode
translation
> > > > program
> > > > > that should be available soon! More details when past beta.
> > > >
> >
> >
> > Be sure to visit the group home and check for new Bookmarks and
files:
> > http://groups.yahoo.com/group/Homebrew_PCBs
> >
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> > Homebrew_PCBs-unsubscribe@y...
> >
> >
> >
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