Spiraling vertical lines on vase mode (Sovol 6 plus)

I printed this in vase mode using 0.2 layer height and 0.9 line width using a 0.4 nozzel. The printer left several spiraling lines on the print. Any ideas on what caused this?

Check the tension on the Y Axis…increase it a little…maybe 10mm.

I increased it, and attempted printing the same file again, it did the spiraling lines again.

10mm was more of a guess.
I originally had a 1/4 turn, but thought that was a bit much.
I don’t know how loose your belt might be, keep trying.

I printed it a couple more times, changing the belt tension each time, and still have the same results. If it isn’t the belts, what else could be causing it?

Have you considered testing a conventional bead ratio ?

in my opinion the belts should be tight enough to give a sound when plucked( ie strumming the belt) the higher the pitch of the pluck sound the better, but is this print from a computer, a octoprint or a sd card?

I had a similar issue with Octo4a, my phone couldn’t keep up. This doesn’t look like that. Have you tried with a lower extrusion rate. 0.9 for a 0.4 nozzle seems a bit thick.

These lines are consistent with the micro layer changes that vase mode makes, stepper motors still step on changes so it isn’t as smooth as we wish it were. When it does the small height change there won’t be as much “squish,” causing the lines you are seeing.