Pen plotter uses polar coordinates

To track a location in two-dimensional space, two measurements are needed. Most of the time, one would naturally think of doing this by the Cartesian method, measuring position along one axis and then again along a second axis. But that’s not the only way to track location. Polar coordinates, where the distance to the origin and an angle are used as two measurements, work just as well and can sometimes be a preferred method. This pen plotter rejects the expected Cartesian methodology we generally expect in favor of this polar system.

The first prototype built by [André] was a good proof of concept. A pen attached to a movable carriage on a single rotating arm produced passable drawings, but like all prototypes, this one needed some tweaking. Limit switches at the ends of the table, as well as inside the arm, served to orient the plotter so that it did not need to be manually reset each time. A linear actuator has been added to allow more precise control of the pressure of the pen on the table, and finally an encoder has been added to the base of the plotter to more precisely correct position errors in the rotary arm mechanism.

All told, the Polar Coordinate Plotter seems to work just as well as its Cartesian cousins. Orienting it in this way also has certain advantages. Specifically, it's more suited to drawing curves or circles than an X-Y device, as we've seen with this similar sand drawing plotter. Also, if allowed to rotate through its full 360 degree range instead of the 90 degrees shown in the video, a machine like this could theoretically reach a wider workspace more easily than other plotters. p>