How to effectively eliminate stringing in 3D print I'm having this stringing problem that happens when the machine moves and when it's not supposed to print that I still haven't effectively solved. I will try exemplify with the following image. 



We can see it leaves some prints when it's not supposed to. 

I know we can try to solve it with the retraction properties, but is there a way to calculate the right levels of it?

How do you guys do it?

My setup is:


Ender3 printer
Ultimaker Cura sw
BQ filament


Info about this particular filament, from store.bq.com

DIMENSIONS AND WEIGHT


Weight - 1 kg
Filament diameter - 1.75 mm
Coil size (diameter x width) - 175 x 77 mm
Spool axle diameter - 44 mm
Enclosure - 187 x 187 x 83 mm


MATERIAL


Composition - 100% PLA (Polylactic acid).


PRINTING FEATURES


Optimum printing temperature - 205 ºC
Printing temperature range - 200-220 ºC
Note: The image in the question was changed after the question was asked. This answer is out-of-date with respect to how the question has changed; I'll update it when more information is available.



These don't look like strings, which I'd define as material deposited outside of the model, but rather damage done by moving the hotend through already-printed material without retracting. In Cura, this is called "retraction combing", and it defaults to "all", which is way too aggressive and visibly harms the surface finish. Switching it to "noskin" or even "infill" only will make this go away and greatly improve your print quality, at the cost of some speed. The cost can be severe in worst case with certain kinds of fine detail, but usually "noskin" is cheap and suffices.