EDIT - July 12, 2024: I've now added files for values lower than 100%, starting at 25%.

These test tiles can be used to determine the best initial layer flow setting for your printer. Ideally, you want a solid first layer that is perfectly uniform. You don't want to see gaps between the lines (under-extrusion, like my 100%), but you also don't want ridges or waves in the top surface, or inconsistencies in thickness (over-extrusion, like my 180%). Because of their thin nature, the squares can be held up to a light to help see any abnormalities/artifacts after printing. Usually, if any setting other than 100% is best, that means you should adjust your z-offset, but if you've already tried that (or are just lazy like me), changing your initial layer flow multiplier can be a good workaround.

Each square is labelled in increasing 5% values, starting at 100 and going up to 200 (I may add values lower than 100 in the future). Just change your initial layer flow setting to match the number on the tile. By doing this - and with the inclusion of a small hole at the top - they can be stored on a keyring for future reference.

I've also included picture instructions to aid anyone who may not know how to change settings per-part. Cura is usually my slicer of choice, which is why its instructions are much more in-depth. As far as I'm aware, PrusaSlicer doesn't allow for changing the initial layer flow setting (outside of manually editing the g-code, which is beyond my skill/patience level), which is why there are no instructions for it.

A few side notes: 1.) These squares were designed with a 0.2mm layer height in mind, though you can certainly use a smaller value, as long as the main part of the tile remains one layer thick. 2.) I designed these and have only used them to test initial layer flow. The idea was to see how far I could push the setting without experiencing over-extrusion, and to see how over-extrusion would affect the subsequent layer. However, I would imagine one could also use these to test the general overall flow setting, seeing how the increased value affects the finer details of the text on the second layer. By scaling the X and Y values, you could also probably use these to test bed leveling, but that wasn't my intention when designing them, and there are most definitely better designs out there made specifically for that purpose. 3.) Rarely, and depending on certain circumstances, if you push your printer's flow too much, you may hear grinding from your printer. This is because so much filament is trying to be extruded that it doesn't spend enough time in the hot-end to melt. This grinding is obviously not a good sound to hear, and if you do hear it, stop the print as soon as possible. 4.) If you have a particularly grippy bed, you might have a hard time removing them, even after the bed has cooled (for instance, I have a textured PC bed that was included with my S1 that holds on to parts for dear life). However, your run-of-the-mill PEI plate should have no problem letting go, especially after being left to cool. 5.) Any suggestions/constructive criticism on how to improve these would be much appreciated, as I'm very new to 3D modeling and I definitely don't know a lot about it.