Cable-Driven Tool Changer System

Update! This version has now been superseded by a more mature [version 2](https://www.thingiverse.com/thing:3805144). I will leave this one up for reference, though.

[Demos for the curious!](https://youtu.be/yCwlqF1J5I8)
Long-form writeup can be found [here](http://www.doublejumpelectric.com/projects/toolchanging_pen_plotter/2019-03-17-toolchanging_pen_plotter/).

Let's kick things off with a quick video summary of the [tool changer](https://youtu.be/ibJpjYAcjaM) and [parking post](https://youtu.be/QcsXqRd0ouY).

And let's throw in some quick [repeatability testing](https://youtu.be/TebSZKkX770) for good measure.

Note: CAD files on this project are finished, but full integration onto my 3D printer is still a work-in-progress.

This project is a complete solution for tool-changing, including
* a highly-repeatable tool locking/unlocking mechanim
* a generic tool base with reliable geometry for parking that can be adapted to many tools such as 3D printer extruders, pen hold