[ Bill Budenholzer wrote in 160418 MMDigest:

> Has anyone considered using one of these [vinyl cutting machines]
> to cut music rolls?

I have a vinyl cutting machine that was not very expensive and it works
remarkably well cutting vinyl and also paper.  However it is not the
ideal machine to make paper rolls for a variety of reasons.  Although
when properly adjusted it can make tiny holes lines, etc. (I have made
vinyl stickers of things such as a banjo with strings), it is quite
slow and would probably screw up at least a few holes now and then
which could be very difficult to repair.

If the paper is not held down very carefully, or if the knife becomes
at all dull, it would probably do closely spaced holes very badly.
Bridges in paper are almost certainly going to be a problem.

The idea of carving the roll is also headed in the wrong direction.
I have several programs that convert images to Gcode and when using
line art as a source the images can be used to cut holes in flat
material.  However, carving a hole in paper would be virtually
impossible.  I do not know of any tool that could possibly do a decent
job other than a laser.  If you want to use a laser there are other
better ways than converting an image.

Since the source files are in MIDI which is a very efficient way to
store piano roll data, it makes the most sense to convert MIDI to Gcode
and to use a suitable punch that just punches the holes rather than
carving or cutting them.

Writing such a program would not be very difficult.  I already have
the code that converts note by note MIDI files to line based punch
positions.  It has been years since I looked at it but it includes
a facility to print a proof text file showing the hole positions so
I knew I got this part of the job right because the printed sheets
match the original roll.

All that would be needed to convert to Gcode is to create a position
map for each roll format that had the position on the paper for each
MIDI note and that created a move command (G01 in Gcode) to that
position with the Y position being the paper advance.  The Z axis could
be used to do the punching if using a step motor for the punch ram or
on off spindle control could operate a relay if using a solenoid.
Using Gcode allows for the use of standard hardware and software,
minimizing he need for any special programming other than converting
MIDI to Gcode and I have already done the hard part of that job.

The other sensible approach would be to use an Arduino microcontroller.
There are libraries that parse MIDI, control stepper motors with
acceleration and to control relays, etc, etc.  Microcontrollers are
the way to do this sort of job today.

Spencer Chase
Garberville, California