so what causes this?

[printbus]

TJC beat me to it. Sniffle, clarify how the X & Y axes are oriented when you print. When I see ringing, it's usually on the side parallel to Y. Rereading TJC's post, I think he's saying the same thing. It's ringing because it fades away. Also notice how the interval between the ringing pattern increases - this is because the printer is accelerating away from where the ringing started. As it speeds up, the ripples will be farther apart.

Fine and dandy. I personally think there are issues in Marlin move planning.

A counter argument to ringing in this case is that we're not at a 90 turn. At least not one where the axis was running full speed before decelerating to the corner. My 90 degree corners come out pretty clean. Where I tend to always see ringing, and sometimes substantially, is on shallow artifacts like your lettering or on holes in relatively thin sidewalls. In the case of your lettering, the print is moving along, stops at the recess created by a letter, shifts slightly perpendicular to the direction it was going, and then reverses direction. At least that's what I've watched my printer do. So, the ringing is supposed to be caused by that little bit it shifts for the depth of the letter recess? That's hard to buy.

Same thing for holes on a thin sidewall. Just yesterday I printed a small project box with a large hole on a 1.75mm thick sidewall, and got substantial ringing on one side of the hole. The x carriage built up a lot of momentum crossing that 1.75mm sidewall? The 90 degree corners came out far cleaner than the hole. The inconsistency is what causes me to question what Marlin is doing. EDIT: It's almost like the X motor is being twitched during that turn-around in the Y axis - like Marlin is not starting the X movement out slow. The jerk setting should influence this, but again, 90 degree corners come out fine. I really wish my oscilloscope had storage capability so that I could monitor what the driver signals look like for the X and Y motor where I see this ringing occurring. If nothing else, I may rotate that object and reprint it just to see what kind of ringing I get on the hole when it is parallel to X. With the aluminum v-rails on the i3v, I have a hard time understanding how the Y-axis is any less laterally rigid than the X-axis.

If you want to experiment, the settings involved would be DEFAULT_XYJERK, DEFAULT_MAX_ACCELERATION for the axis perpendicular to the one where you see the ringing, and DEFAULT_ACCELERATION. Details on how these interact are discussed in thread Marlin Motion Related Configuration.h Settings for MakerFarm i3v. It could also be argued that your belts are too loose. Others might argue too tight. Carriage wheels could be adjusted too loose.

Hoping to hear other opinions on this.