Hi,
I've logged way more hours than I care to remember on a Exelon bottom drill
and it was hands down the best way to drill accurate holes in PCB
prototypes. The largest board I did as I recall had about 4,500 holes. Only
broken drills were when I did something stupid like not set the feed
correctly. We normally drilled boards 5 up. I had replaced the original pure
optical targeting with a B&W CCTV camera (it was the mid 70's). The
alignment was easy. Turn-on the camera and monitor, let them warm-up for an
hour. Then we drilled a single hole in a waste area with the board clamped
in position, taped a large target to center the hole. A .030 hole was about
5 inches across, you would be amazed at how accurate the human hand is with
good visual feedback. The nice thing about the bottom drill was all the
waste was on the bottom so the optics stayed clean.
Anyway I've moved on from the PCB business after the EPA started closing
down the small PCB houses. Now working at Microsoft as a SAN engineer and
doing hobby CNC systems in my spare time. The point is I use a very nice
software package called CentreCam for optical alignment/edge finding and
measurement on my CNC.
I have no association with them just like and use their product. With it you
can overlay several different types of targets on a webcam image. In the
link provided just click on the Software Download button. You do need to
provide Email, Name and Country I've never gotten any spam from them.
http://www.miketreth.mistral.co.uk/centrecam.htmThanks,
Ron Cody
KF7MKY
"Good decisions come from experience, experience comes from bad decisions."
-----Original Message-----
From:
Homebrew_PCBs@yahoogroups.com [mailto:
Homebrew_PCBs@yahoogroups.com]
On Behalf Of Henry Liu
Sent: June 09, 2011 11:22 PM
To:
Homebrew_PCBs@yahoogroups.comSubject: Re: [Homebrew_PCBs] Precision Drilling of PCBs
If you have a motorized XY table (such as a CNC sherline mill), you could
mount the camera with some cross hairs and have a drill button that will
offset correctly automatically and drill.
Alternatively you could use a manual XY table with a digital readout and
again offset the known distance. You could even do it manually. Your work
flow would be see hole in crosshairs, move known XY offset, drill, move back
known XY, repeat.
Henry
On Thu, Jun 9, 2011 at 3:09 PM, Lawrence Kincheloe
<
lokimail@...>wrote:
>
>
> If I understand the problem correctly...
>
> An easier solution might be to map out the distortion using something like
> grid paper and use a clear stencil for "cross-hair" like grid lines.
>
>
> On Thu, Jun 9, 2011 at 4:30 PM, Leon Heller <leon355@...>
> wrote:
>
> >
> >
> > On 09/06/2011 20:51, Boman33 wrote:
> > > A very long time ago commercial hand drilling was done with the drill
> > > mounted under a table and a microscope with cross hairs was used on
the
> > top.
> > > The drill was on an air cylinder so when things were lined up a
> > footswitch
> > > was pushed. No parallax. A similar rig was also used to create a NC
> paper
> > > tape so additional boards could be drill automatically.
> >
> > They had one of those at a French university where a friend of mine
> > works. I tried it out when I was working there, and it works very well.
> > They got rid of it when they closed down their in-house PCB fabrication
> > facility. It was made by Excellon, who invented the drill file format
> > that we still use. Someone in the UK actually offered me one of those
> > machines three or four years ago, but I wouldn't be able to get it up
> > the stairs here.
> >
> > Leon
> > --
> > Leon Heller
> > G1HSM
> >
> >
> >
>
> [Non-text portions of this message have been removed]
>
>
>
[Non-text portions of this message have been removed]
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