Plotters and drawing robots are fun projects that let you create art with all the precision and perfection that computer numerical control can deliver. [TUENHIDIY] demonstrates that ably with the Multicolor DrawBot.
The build relies on a simple XY Cartesian design, using a pair of NEMA 17 stepper motors. It’s built in the typical CoreXY fashion, running GRBL firmware on an Arduino Uno.
Where [TUENHIDIY] gets creative is in the pen itself. Rather than using a simple ballpoint or marker, instead, a retractable multicolor pen is used instead. With the multicolor pen on board, [TUENHIDIY] notes the importance of limit switches in the design. These allow the the ‘bot to make multiple passes, each time in a different color, to build up a multicolor image. Without the limit switches in place, it would be impossible to line up each following pass.
We’d love to see the build taken even further with a servo-based system for switching colors automatically. As it is, though, [TUENHIDIY] has a capable plotter that can deliver tidy multicolor artworks.
One of the more curious applications of plotters of late are those used to send faux handwritten letters through the postal system. Video after the break.
It’s not impossible to line up each colour without limit switches (which in this case should be called homing switches). The coordinates don’t change between jobs, so if you didn’t have homing switches then for a multicoloured drawing you can just send each layer without homing between layers. Basically you’d set the origin manually before starting the job.
> Without the limit switches in place, it would be impossible to line up each following pass.
“Impossible”, unless you just keep the motors powered while switching colors. Nothing hard about that…
Or home against a hard stop by deliberately stalling the motors.
Or just push the axis to their physical end before powering up the device.
There really is nothing special about homing switches.
concerning homing against a hard stop. some of the trinamic stepper motor drivers can detect when a motor hits a physical stop by the increased motor current.
I’ve been looking at this type of plotters on Aliexpress for some time, but I can’t quite grasp why these are more expensive than the versions in a rectangular frame. They need less material (shipping costs etc).
The reason I’m interested in this type is because they are quite easy to store compactly with a few small modifications. You’d just have change the design so the X-Y plate is made up of two parts or has a hinge in it, so both axis can be collinear for storing it. It’s really such a simple Idea that I find it strange I do not see this in the wild.
Every layer on my Ender prints fine without re homing to the XY limit. As long as you don’t miss any steps should be fine. Also this is max 4 layers?
I may be missing a detail that would explain my confusion