By Steven Wasser - President, Verne Q. Powell Flutes
What’s in a name?
In this case a lot, but the name itself is something we just made up
because it sounded like fun.
Zinki is the name we’ve given to Powell’s patented
process for extruding tone holes on one of our CNC machining centers.
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The "Zinki" CNC Machine |
The traditional process for extruding tone holes generally involves at
least 3 separate steps, each one involving a different setup on a different
machine, as follows:
1. Make
a small hole in the tube where the tone hole is going to be. Usually this involves drilling or punching an
egg-shaped hole.
2. Load
solid pulling balls into pockets in an arbor, then slide the flute tube over
the arbor and place on a machine. Position
dies over each tone hole. Connect a spinning
shaft to the pulling ball and pull up through the die, pulling flute tubing with
it to form the tone hole.
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Traditional pulling ball. |
3. Remove
the tube from the pulling arbor and place it on another machine. Face each tone hole level with a cutting
tool, then use a special tool to roll over the tone hole edge to (a) eliminate
the sharp edge and (b) reinforce the tone hole.
The process normally takes 30-45 minutes and uses both
extrusion - a brute force technique - and spinning to form the tone holes. The force required has a tendency to pull
metal from the tube into small ripples alongside the tone holes. And each time a flute tube goes from one
setup to another, accuracy is lost.
Powell’s Zinki technology delivers the pulling
ball from the outside of the flute tube, rather than pre-loading it on an arbor
inside the flute tube. In order to do
this Powell needed to figure out how to put a big ball through a small hole. Instead of a single large ball, the Zinki pulling
ball is actually a series of small balls which can expand and contract. The details can be
viewed at U.S. patent #7,420,109B2.
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Close-up on Zinki pulling ball. |
With Zinki the balance between extrusion and
spinning shifts to spinning. The result
is a highly accurate tone hole with little if any rippling on the tube.
The last step in Zinki is to “kiss” the top of
the tone hole with a diamond facing tool to make sure that it is level.
And all this takes place in a fraction of the
time for traditional tone hole extrusion.
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Powell Conservatory (Drawn Tone Holes) |
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Close-up on drawn tone holes. Red arrow points to the rolled edge. |
I like your post and it is so good and I am definetly going to save it. One thing to say the In depth analysis this blog has is trully remarkable.
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Very interesting...I have a Powell Sonaré PS-709 & as I've learned more about the Powell flutes in general I've been curious about what made your drawn tone holes different. Now I know! Thanks Powell!
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