Adam,
The Excellon Uni-Drill uses a dc motor and lead screw to move the
spindle up and down. There is a series of adjustable limit switches
to set the travel distance. The air operated clamping "foot" is
between the optical scope and table surface and clamps the board
before drilling to prevent movement that would break drill bits.
When the foot switch is depressed the pressure foot clamps the board,
spindle travels upward, drills through the panel, drill retracts and
the clamp releases. You can watch the drill bit come through the
board in the screen.
The Nawide and Aetna machines use an air/hydraulic spindle feed with
the feed rate controlled by a needle valve. The Nawide machine is
very quiet because it has a dc motor and belt driven spindle. Any of
these machines can also be operated with a stylus and drill template.
The optical scope is used to make a master template and then the
stylus is used to "trace" the template pattern and drill the board.
An experienced operator can drill 80 holes per minute in a stack of
three boards in the stylus mode. If I'm drilling a single lot
prototype I just use the scope at about 20 holes per minute.
If there is any interest I will post some photographs of these
machines which would answer most of your questions. You would be
impressed with the accuracy of these machines not to mention the ease
of use and reduction of operator fatigue.
Tom
--- In
Homebrew_PCBs@yahoogroups.com, Adam Seychell
<adam_seychell@y...> wrote:
>
>
> twb8899 wrote:
> > Adam,
> >
> > I like your drilling machine. If you flipped it over and put an
> > optical scope and air clamping foot on it you would have almost
the
> > same machine John is referring to. There were several
manufacturers
> > of these machines with the most popular one made by Excellon. It
was
> > a Uni-Drill model 1230. The actually came with a stylus assembly
for
> > template drilling and the optical scope was optional but almost
> > everyone bought the scope.
> >
> > They use a Precise #65 spindle with a variac speed control. You
can
> > still find these machines if you look hard enough but many of
them
> > went to the dump which is a shame.
>
> That would be a sore sight. Although I can understand many
> professionals simply have no use for a manual drill machine. I've
> heard the stories about the PCB business going through a rapid
> change in 1980's, even here in Australia. One business man told
> me the only places who survived were the ones who could get the
> new and automated processes working the quickest. This guy's
> business specializes in low volume, DS PTH, aimed at a lower cost
> solution for prototyping. He knew of PCB fabricator that went
> under, simply because they had reliability problems in the new
> plated through hole line.
>
> Unfortunately I haven't seen any of the drill machines here in
> Australia. I'd be very interested just looking how they are
> built. How was drill feed operated ? Was this foot pedal control
> or more elegant motor drive feed or hydraulics ? For quick
> experiment I attached a bike brake cable to the arm on my
> machine, hoping to operated the down feed by pulling the cable.
> It turns out there is far too much friction in the cable and you
> loose the "feel" and fine control of the drilling.
>
> What is an "air clamping foot" ?
>
> I'm imagining foot control would make drilling a lot easier
> because it gives you two hands to position the PCB for drilling.
>
> Adam