Homebrew PCBs

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.
> > > > >
> > >
> > >
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> files:
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> > >
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> > >
> > >
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