I made this model because I wanted a better way to tune retraction. I needed to assess retraction performance on both small and large travels and be able to tune the retraction minimum travel (Cura), which decides the travel distance below which no retraction will be made to eliminate useless retractions, which cost time and needlessly wear down the filament. You can see the travels without retractions (dark blue) and with retractions (light blue) in the picture.

The model provides gaps of increasing distance, starting at 0.25mm and doubling in length all the way to 64mm. The last pillar is offset from the rest so the nozzle doesn't run back across all the previously printed pillars. The stated gaps are between the outside of the pillars (not the center), so the actual travel moves will be slightly longer, because the nozzle finishes a pillar on the inside wall, and starts the next pillar with the outside wall. Make sure you configure your slicer to print outside walls first, so you can see if blobs appear on layer starts after the print is done. After dialling in retraction distance and retraction speed, play with the retraction minimum travel to see which travel distances need a retraction and which don't.

The model fits on the smallest build plates and takes less than 10 minutes to print. There is also a version with taller pillars.