On Wed, 14 Dec 2005 19:25:31 GMT, jimbo <jimREMOVE@xxxxxxxxxxxxx>
>The way the device works is that the drill bit is a soft metal
>tube driven by the piezo unit in a slurry of cutting grit (~100
>grade silicon carbide) in liquid (mineral oil or water). The
>action of the tube pounding grit against the substrate (jewelry
>bead, gem, or anything with a hardness lower than that of the
>grit) simultaneously eats away at the bit and the substrate, thus
>drilling the desired hole.
> From the design specs of manufactured multi-thousand dollar
>units, it appears that I want something that drives a
>piezoelectric transducer at around 40kHz.
>I'm starting from square one. I can wield a soldering iron and
>have played with the 300-in-1 type electronics kits a bit over the
>years, but am not at the point of being able to design a circuit
>for anything like this.
>It appears that I need suggestions for:
>1. a signal generator capable of operating at 40kHz (am willing to
>experiment with different waveforms to see which is most efficient
>2. an amplifier
> - capable of good slew rates at 40kHz
> - high input resistance matched to the piezo transducer
>3. good candidate piezo transducer
>Thanks for any help in advance.
Many industrial piezo devices typically run at high voltages
(1000 V is not uncommon), which makes the amp design a
problem even if you are a pro. One alternative might
be to tear apart a plastic piezo horn tweeter. Some of
these have decent response up to 40 kHz, although the
response has many dips and peaks. You'd want to
tune to the nearest peak, whatever the frequency.
That will depend on the mechanical structure that
you come up with to couple it to the cutter bit.
My guess is that despite herculean efforts to reduce
mass, this is not going to be in the same ballpark
as the commercial units as far as cutting speed.
The piezo tweeters just can't handle all that much
power. But it might be fun to experiment with!
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