Re: Milling Circuit Boards

Hi Alan,
I laid out my design on .1 grid paper. Then in TurboCad
I turn on the grid! I then redraw the traces ending them at
the nearest line. All the traces are square in nature. Since I
deal with digital signals, the size of the trace can be larger
than needed.
Like I said, the trick is in the drawing! Make the outline
of each trace one continous line. You can click on turns, but
don't hit finish until you come back around to the beginning of
the trace. Draw the board in four or more sections. Don't jump
around, drawing a little here and a little there. If you jump around
your machine will spend more time moving than cutting. If you hit
finish several times on one trace, you will be treated by see the Z
axis move up than down for no reason.
Save the file in DXF format. Import into KELLYCAM and
SCALE and OFFSET the drawing. I also use the FIND and change
feature in KCam to fix some rapid speed moves that get mixed
in. I am only milling at 5" per minute. I designed my machine to mill
wax and plastic. So far the machine is performing well. I have made
ten six IC circuit boards so far. I am getting 5 boards per milling
bit. I am using the mechanical etching bits from Think and Tinker.
They say to run the bit at 30,000 rpm. I am running at 3,000! I put
three drops of motor oil on the board and then spread it around.

John

--- In CAD_CAM_EDM_DRO@y..., Alan Marconett KM6VV <KM6VV@a...> wrote:
> Hi John,
>
> Thanks for the update. Sounds like you had best results by drawing
in a
> CAD program, doing the outlines as toolpaths? Perhaps you'd like to
> share the .DXF and Gcode files for this or a smaller example? I'd
like
> to study it!
>
> Must have been a lot of work to do the offsets for each "trace
island".
>
> Alan KM6VV
>
>
> kleinbauer@j... wrote:
> >
> > Hi All,
> > Here is an update! After spending countless hours using
> > TOPO,TurboCad,Eagle and Target here are my findings. TOPO will
> > take a BMP and turn it into a DXF. The problem with using TOPO
> > to make circuit boards is, the program adds tons of up and down
> > commands. The conversion is also plagued with the traveling
> > salesman syndrome.
> > Eagle with it's script looked great until I did a larger
> > circuit board. Three 14pin ICs and some traces resulted in 16,000
> > lines of code.
> > Target had the same problems as Eagle to a lesser degree,
but
> > the program is not a easy to use as Eagle. I went back to TurboCad
> > using a new approach. I found out that when you convert a DXF to
> > a Gcode file, the machine will move the same way as you drew the
> > outlines. The trick is to stay in one area at a time and to draw
> > as much outline at one time as you can before hitting finish. Make
> > each trace of the circuit board one long line. Then hit finish. If
> > you draw each trace as several seperate lines, the machine will
move
> > up and down for each line. Jumping around on the drawing to
touchup
> > or correct will result in a final GCode that will move the same
way.
> > I have a GCode file that makes a six IC circuit with
twelve
> > transistors.(4"X6") My machine takes an hour and twenty-minutes to
> > mill the board. I am hoping to cut this to 60 minutes while adding
> > starter holes for components.
> >
> > John