Re: Milling Circuit Boards

Hi John,

Thanks for the comments. So KellyCAM can do offset on a .DXF file? And
output Gcode, or cut it? More ways to do things! 5 boards per bit
sounds a little rough, but then I haven't priced the bits at "think an
tinker". Ballendo has posted previously that a Dremel mill can be used
to replace the spindle of the Sherline (and provided a drawing), so that
might work for you too! I have a pair of 12" ball screws with light
motors that I'll eventually press into this service, after a few of my
"other" projects get done!

Alan KM6VV

kleinbauer@... wrote:

>
> 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