It may be surprising to outsiders, but cartography is a popular hobby. That can include both people who simply enjoy collecting maps and people who like to create maps. If you visit a forum for cartography, you will find all sorts of interesting discussions about the multitude of map projection techniques, debates about coastline measurement methodology, and resources for data. We are fortunate enough to have accurate map data for the entire planet readily available — aside from the ocean floors, of course. Christopher Getschmann wanted a way to use that data to create some wall-sized maps for art and built this massive pen plotter specifically to draw them.
Pen plotters are machines that can automatically draw imagines or write text on surfaces using pens, markers, or pencils. These days, they’re most often used to produce large format technical drawings. Those are usually setup with a pen that moves linearly across the Y axis, which draws on paper that is fed by rollers for a practically infinite X axis. But those can only draw on flexible material (paper) and can’t draw on rigid sheets of material. Getschmann’s DIY plotter can draw on anything that it can be placed against, which gave him the ability to plot maps out on large sheets of cardboard that he was then able to mount to his wall. When placed next to each other, those sheets form a huge map that covers almost an entire wall.
Getschmann’s pen plotter is setup a lot like a CoreXY 3D printer, with the belts running from stationary motors to pulleys and then to the X axis rail and the carriage that moves in the Y axis. The advantage of this design is that it keeps the moving weight down and that it allows for easy assembly and disassembly. The latter is important for storage given the large size of the plotter. The pen is lifted and dropped with another stepper motor, instead of a servo motor like we normally see. That keeps the weight down.
The motors are controlled by an Arduino Nano via TMC5160 silent stepper drivers. A second Nano monitors those drivers for stalls, which eliminates the need for limit switches. Pre-processed data from OpenStreetMap is used to create the huge map to be plotted in SVG format. That is then converted into G-code commands for the GRBL firmware to follow. Only a single color can be plotted at a time, so Getschmann had to make multiple passes for each sheet. Those sheets were then attached to 2x4s that were mounted to his wall, resulting in beautiful art that covers an entire side of the room.