I have been mulling over building a piano roll punch.  I have looked at
the videos on YouTube and think that a single punch is way too slow and
requires programming skills beyond my capability.  A laser-based cutter
is intriguing but the cost of a laser cutter is quite high still.

I am thinking about building a true perforator using solenoids,
punches, servos, and a MIDI output board similar to MIDECO

http://www.midi-hardware.com/index.php?section=prod_info&product=MIDECO&R2=USD 

A die would be made to guide each individual punch through the paper.
A solenoid would drive each punch.  Each output from the MIDI decoder
would control one solenoid.  When a MIDI note is triggered or carried
over the solenoid would be activated ultimately creating a punched hole
in the paper.  The paper would be advanced by through the punch, a line
at a time, controlled by the clock of the MIDI decoder.

By using a MIDI decoder no special programming would be necessary.
A MIDI Type O file would need to be cleansed of extraneous information
not relating to note on/off or at least ignored by the decoder.

I estimate that creating the punch mechanism to be the most expensive
and time consuming activity.  I would prefer to do this myself (I have
a heavy-duty vertical drill press) rather than shopping it out to a
machine shop.  I haven't determined if I am capable of making the
punches themselves.  Each punch would descend into a mating die to
enable a clean cut rather than a torn punch (very similar to a plastic
comb binder hole punch).

I am assuming that the solenoids would have enough force to drive a
punch through the paper directly.  Some of the perforators I have seen
appear to use solenoids to set the punches in the "active" position
then a bar pushes the punches down en masse.

I invite comments and ideas.

Mark Williams
Washington, D.C.