Using this web tool requires trial and error to generate good looking Spirographs. Start by playing around with the perimeters shown below.
In my case, I have a 2D plotter with a vertex at the bottom left corner and a space of 225mm x 225mm. To make sure the Spirograph fits, X and Y values must be between 0 and 225. Knowing this, I used 24, 16.4, and 24 for R, r, and d respectively. After clicking run, G-code appears in the result window. My G-code was then copied over to a G-code simulator.
Looking at the bounds, the Spirograph does not meet the requirements of my 2D plotter. If I was to run this G-code, it would crash and possibly break my plotter.
To Fix this, I changed the Spirograph equation by adding a value slightly higher than 31.6 (40)
This time when the G-code is copied to the G-code simulator, the dimensions fall between the limits of my plotter. To run the Spirograph on my plotter, the G-code must be saved to a G-code file. This is done by pasting the G-code in a text document, and renaming the .txt file as .gcode.