June 21st, 2022—
Pen plotting projects are everywhere nowadays, with the vast majority using a couple of stepper motors for moving the writing utensil and a servo to raise or lower it. But they are quite slow due to the lack of rigid assembly and because the servo motor takes around a second to move the pen. This problem is what drove YouTuber IV Projects to create a very novel design that swaps out the servo for another stepper motor and drastically increases drawing speed.
Just like most other pen plotters, the X-axis is driven by a NEMA17 stepper motor with a timing belt attached to the central pen carriage. However, the Y-axis takes a different approach by relying on a pair of rollers that are covered in 120-grit sanding bands, which help to grab the paper securely and move it whenever the stepper motor rotates the drive wheel. This helps to minimize slipping compared to rubber rollers and is much faster than a belt-driven design.
Perhaps the most interesting aspect of this plotter is the lack of a servo motor for lifting the pen during travel movements. At the top sits one more NEMA17 stepper that spins upwards or downwards to lift a paddle which, in turn, raises the pen off the paper. Controlling the three motors is an Arduino Uno running the GRBL firmware that receives G-code and transforms it into physical movements.
You can watch IV Projects’ video to below see the design in more detail.