Hi Alan,
I don't mind the short life of the tool, its the
cost. The bits are $7 each when you buy ten and you have
to buy ten!
I am milling at 6" per minute with a Dremel. That's
15,000 RPMs. The bits can move .0004" to .0006" of feed for
every RPM. That's the speed limit. So if you own a Taig or Sherline
you are out of luck unless you bought the 10,000 RPM spindle. That
gives you 5" per minute for $1000 worth of machine. Alot of the
EXPERTS out there never mention this. This is how I know they have
their boots on and their shovels in hand. There are no bits out there
that can mill boards with slower spindle speeds unless you
slow the feedrate down to a snails pace. Have you ever droped by
Think and Tinker? That where I get my bits and info.
A real circuit board machine has a 20,000 to 50,000 RPM
spindle. I ran my Dremel at 20,000 for awhile. 15,000 RPMs gives
me good Dremel and bit life. I have made over 200 4" X 6" boards
to date. I save the old bits. There are people out there that
do re-sharpening. I might even give it a try myself.
John
--- In Homebrew_PCBs@y..., Alan Marconett KM6VV <KM6VV@a...> wrote:
> Hi John,
>
> Thanks for the comments. I hadn't looked for PVC on ebay. Should
be a
> lot cheaper to ship then BRASS! I have some Plexiglas, but I doubt
if
> that is suitable. I've heard of some dense foam (PDF or
something??)
> that is used on routers, but I have no source for it.
>
> I'm aware that PCB stock is available in 1 and 2 oz foil weights,
but I
> hadn't heard of the copper being any more or less soft. Copper WILL
> work harden, but that shouldn't apply here.
>
> Yes, milling a board first is a FAST way to get a prototype, and if
a
> Gerber file is generated, then the files can be sent off for
commercial
> boards.
>
> I'm a little dismayed at the short life of the bits. Especially if
they
> don't make it through a complete board! What speed spindle do you
> have? I have a Dremel tool that will have to do for a while.
>
> Yes, you are certainly doing OK for a $125 machine! After that,
it's
> the "law of diminishing returns", I'm afraid.
>
> Alan KM6VV
>
> crankorgan wrote:
> >
> > 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
> > > >
> > > > To unsubscribe from this group, send an email to:
> > > > Homebrew_PCBs-unsubscribe@y...
> > > >
> > > >
> > > >
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> >
> >
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> >
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> >
> >
> >
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