...with a bit more thought:
I would like to use somewhat commonly available hardware-i.e a plotter or Lego Mindstorms.
1. My pen plotter idea is out (for now) as moving the calculator around,AND transferring the mechanical movement of the pen dropping is very difficult (for me). The plotters that are commonly available (HP7550, 7475) are not true table top plotters, but move the paper within pinch rollers (in the y direction).
2. The Lego RCX does have three motor outputs (X, Y and Pen) and three inputs - certainly sufficient for this task.
I will pursue #2 for now - as time allows!!!
Of course, we will still have the mechanical problems:
1. Aligning each particular machine (35s, 42s, 15c etc) will require unique 'tooling' to hold the calculator properly - both in X / Y and vertical distance.
2. Key pressure - I believe that the appropriate type of damping material along with limiting the vertical 'drop' of the pen will take care of this.
3. Certainly feedback will be an issue, as the robot will not have vision to ensure that the correct key was hit.
4. Of course, multiple/simultaneous keystrokes will not be possible - although perhaps the user could work in synchrony with the contolling software for the (potentially) few keysteps that would require this.
TomC