Cartesian Plotter

Note 2020-03-04: there is a newer version of this project with many improvements here: https://www.thingiverse.com/thing:4037180

Please also check the full project write-up at:

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This version builds on what I learned with [my previous plotter](https://www.thingiverse.com/thing:3986756). Most obviously, it uses a traditional 'cartesian' design, where movement in the y-axis is provided by a motorized arm, while the drawing surface stays still. This has the benefit of much greater accuracy. It also means that yopu can, in theory, draw on any flat surface.

However the drawbacks are that:

1. It needs much more space. With about 50 cm of travel in each axis, it needs a space that big to store, and 1 m x 50 cm to operate.
2. The long arm (with steel rods in my case) is heavy, so it tends to dip towards the end of its reach. This can cause problems getting the right pen height or pressure. To alleviate this, my design has bolt-down points on the x-axis. By bolting this axis