Re: [Emc-users] cutting spindle

[Ron W. <rj...@al...>]

hi Roland,

yes, air spindles are used for situations where hi speeds are necessary,
such as printed circuit drills where the speeds can go beyond 150,000 rpm.

often the primary issue is bearing life (conventional anti-friction bearings
are rarely used beyond 80,000 rpm) so you also see a combination of
air-bearing, but electric drive spindles (and sometimes with water cooling)
since it is more efficient to use hi-frequency AC drives as opposed to
the cost to operate a compressor and dry the air (at least in an open
air system).

we also have a machine that uses an air motor to power a slitting saw which
rotates at 15,000 rpm with conventional ball bearings, and the motive was
to get the smaller envelope of the air motor, and again the system is open
air.

your proposal to use air in a closed system without an accumulator tank
is certainly interesting.  for a versatile machine where you might want to
make many interchangeable heads the economy of air tools is attractive,
though i doubt it would be wise if you're building a single head machine.
investigate the air motor's lubrication requirement, there is an upper
limit for vane type machines (that require lubrication) and at the highest
speeds you see turbine motors with air bearings so lubrication is not used.
i would also look closely at the issues of cooling the oil mist as you propose
to rid the system of moisture.  i'm thinking that in a closed system that you
would not have a moisture issue after startup so you could use a dessicant
drier to good effect.  also i suspect that if you choose vane motors that
require lubricant mist that you'll have to inject the lubricant after the
compressor and separate it out after the motor with a coalescent filter,
but would have no issue if you pumped the oil back to the injector thru
a filter to rid yourself of particulate matter scraped off the vanes.

-ron

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On Thu, 27 May 2004, Roland wrote:

> Hi
>
> I've googled on this, but found no real hits.
>
> Do people use air tools as spindle motors for high speed machining?
>
> My idea is that I want to use an air tool, but put a collar on it to
> re-coup the air, and make it a closed loop system, with an air-con coil for
> cooling. That way the lubricant stays contained, for longer life, and so as
> not to mess everything, and the air stays dry.
>
> So the tool can be really high powered, smooth and versatile, but seperated
> from it's bulky power source.
> If you used a multicylinder head, you don't even need a tank.
> How does that sound. Am I missing something?
>
> Regards
> Roland Jollivet