Homebrew_PCBs

I am surprised at the air consumption and that they would use
electric motors for drilling. the motors would be much bigger than a
similar power air motor.

Dave




--- In Homebrew_PCBs@yahoogroups.com, "twb8899 <twb8899@y...>"
<twb8899@y...> wrote:

> Jan,
>
> The big professional drilling machines all use electric spindles

but

> some have air bearings for rotation. These air bearing spindles

have

> no ball bearings and therefore no metal to metal contact.

Everything

> spins on an air cushion with almost no run out. Very small holes

can

> be drilled with this type of spindle. The spindles are electric
> driven to obtain the torque needed especially for larger holes.
>
> All of my machines had ball bearing spindles, however, the spindles
> did slide up and down in a cushion of air for very fast action. The
> XY table also rides on an air cushion against the granite table.
> My favorite machine was an Excellon EX-200 Driller/Router. This was
> considered a "small"(6500 lbs!) machine. It had three spindles and
> could drill or route three stacks of panels up to 12" x 24". It

also

> had an optical scope for digitizing. We used this machine for all

of

> our engineering and prototype work. The original specifications

said

> this machine could drill 400 holes per minute. This was probably

true

> for a .1" grid drilling only one deep. Our average drilling rate

was

> around 150 holes per minute when drilling three panels deep.
>
> I shut off the auto tool changer mode since it just wasn't reliable
> (ask any Excellon service tech!). Several types of spindles were
> available but I used the 60,000 rpm drill/route spindles on the EX-
> 200 and 80,000 drill only spindles on the other machines. The air
> requirements for these machines was about 20 cfm at 90 psi.
>
> Tom
>
>
> --- In Homebrew_PCBs@yahoogroups.com, JanRwl@A... wrote:
> > In a message dated 1/15/2003 2:29:33 AM Central Standard Time,
> > twb8899@y... writes:
> >
> >
> > > Hope this info answers some of the bit questions.
> >
> >
> > Wow! Thanks, Tom! That is VERY useful to us hobby-folk!
> >
> > Yeah, I watched a 4-quill CNC PCB-drill with "pods" change its

own

> bits, and
> > all SEEMED to be fine, but I just could NOT help thinking, as I
> walked away,
> > "This CAN'T be so reliable ALL the time?!!!" GOOD to hear it

isn't!

> >
> > Interesting you say the quill motors are electric. I was told

they

> are
> > PNEUMATIC, to run at 100,000 RPM! Hmmm...
> >
> > Jan Rowland
> >
> >
> >
> >
> >
> > [Non-text portions of this message have been removed]