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MMD > Archives > May 2016 > 2016.05.07 > 04Prev  Next


Homebuilt Piano Roll Perforator
By Spencer Chase

There is a reason that all the conventional roll perforators used
solenoid or pneumatic controlled interposers and a large flywheel-
mounted ram to do the paper punching.  It's because the force to punch
paper is a lot more than you might suspect, especially as the punches
wear. If you are doing a single sheet it might not be extreme but to
punch a single sheet cleanly requires very close tolerance punches.
I doubt that this is within the capabilities of the average person
with a drill press.

You can drill the die guides and stripper all while held together, then
ream them with the correct precision reamers and then harden the steel.
You can buy ready made punches as injection molding ejector pins.
These are made to high tolerance and are already hardened and can be
had with a variety of heads to facilitate punch striking and pulling.

If you want to minimize the force to cut the paper you will want to
grind some "shear" into the punches so the hole will be punched
progressively instead of the whole circumference at once.  My guess
is that a concave shear would be the best for single sheets of paper.
It also has the advantage of being self centering whereas a simple
slanted edge would want to pull the punch to one side which might make
it more likely to produce a hanging chad.  If the die and closest guide
are very close together this might not be a problem.

Also, fitting all the solenoids in the required space will be quite a
challenge.  You would have to use levers to allow the banks of solenoids
to be off the punch line.

There are suggestions (I forget where) that there were reiterating
perforators that punched a roll directly as it was played on a marking
piano but I'm sure it would be a major technical feat to build one.
It would surprise me if they used individual solenoids because of the
difficulty in fitting them all in.

Spencer Chase
Garberville, California


(Message sent Sun 8 May 2016, 00:27:37 GMT, from time zone GMT-0700.)

Key Words in Subject:  Homebuilt, Perforator, Piano, Roll

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