In 2014 I started a project that I called the Arc Printer. The original intention was to make a pretty simple low-cost, low-resolution, large-scale printer that could be used to make poster-sized images. I worked on imitating what these images might look like in software, and was getting ready to start making it, but I changed course and began instead making a wheeled robot version of the project, called the Roving Artist.

Essentially, it’s meant to serve as a sort of low resolution printer which draws pixels that are pie slices (circle sectors) with different inscribed angles. A minimum-value pixel will be a very skinny pie slice whereas a maximum-value pixel will be a complete circle. See the Roving Artist page for much more information and discussion about the project.

Towards the end of this summer, I decided to go back and revisit the earlier version of the Arc Printer, before the project turned into a wheeled robot and became the Roving Artist, and I’ve made some progress building that new old one.

I got to a reasonable stopping point, but with the start of school time has become fairly scarce. Here’s a quick photo tour of my progress on the project, with some descriptions along the way.

arc2 Side view of the device. The PVC pipes are the horizontal track along which the carriage moves.

arc3 Side view of the carriage unit, without the pipes in the way. Note the two motors: the motor near my hand raises and lowers the wooden plunger which has the other motor attached to it. This lower motor will have the paint brush (or sponge, etc.) attached to it. The plunger therefore allows the carriage head to travel without constantly painting.

arc4 View from above. Note that the plunger is square in crossection and hollow. I needed to pretty significantly sand the corners round so that they wouldn’t bind when the plunger was moving up and down. Also note that the servomotor is just sort of clinging to the top of the box; it’s pretty precariously glued on there and the positioning of it like that is one of the biggest design flaws in the current iteration.

arc1 Closeup of the plunger arm.

arc6 I bent some heavy steel wire to make the armature that the pipes fit into. Though of course there’s friction as the carriage slides along, it’s not much and the stepper motor driving the motion can easily overcome it.