Cura Intermittent Retraction Problem. Retraction Not perfromed randomly.

Hi I'm new to this forum and is seeking help on a very frustrating stringing problem. Closer inspection points to the fact that when printing multiple (separate parts) at the same time, the filament doesn't retract some of the time when traveling between the parts causing severe stringing between the separate parts. I've included pictures to show this. I've monitored the printer closely to find that retraction works fairly well within the individual part. The problem appears to be intermittent during travel between parts. After I completed the parts in the picture, I've printed two stringing test posts on the same print right away using the same slicer settings below. As you can see in the second picture, there is no stringing between the posts. The stringing happens when traveling to the 2nd set of tests posts. Again, I've visually confirmed by watching the extruder gear that the retraction within the individual part works most of the time, and works only some of the times during traveling between the separate parts. I also confirmed this by using the same exact settings and just one set of stringing test posts and there is no string at all between the posts. It looked really good.


I am using a Creality CR10S-Pro V2 and Cura slicer 4.7.1.

I've tried many settings but none solved this issue. The settings I'm using which provided a slightly better results in the pictures is below.
Layer: 0.15
Print temp:185c
Bed temp:60
Print speed:35mm/s (tried faster and stringing problem is the same)
Travel Speed:180mm/s (tried slower, no difference)
Retraction:6mm (tried 7mm and 5mm, no difference)
Retraction speed:60mm/s (tried 80mm/s, caused broken filament)
Retraction minimum travel:5mm
Max Retraction Count:10
Minimum Extrusion Distance Window:6mm
Combing Mode: off (tried every setting but stringing only gets worse unless is off)
Z Hop When Retracted: yes
Z Hop Height 0.2mm
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For a new guy here, your post is rather well done, comprehensively described. Considering all the things you've done to narrow the problem, I'm surprised it's as bad as it is. Only one thing jumps out at me and that's the relatively low temperature for the nozzle, although it's usually too-high temperatures that can generate excessive stringing. I'm trying to envision how a too-low temp would cause the problem and my alleged mind comes up empty.

I found a useful web site but it appears that you've already found it and/or covered everything listed and then some.

One thing you've not mentioned is a change of filament. If your spool has been out in the environment and has collected a bit of humidity, you may see a benefit by dehydrating/drying it or using a new previously unopened spool. It's grasping at straws at this point, but should be a consideration.

Hi Fred,

Thanks for responding. I've asked this question on other forums for the past several days and you are the only one that responded. I think I didn't write my question clearly. I've determined that it is not the temperature or the filament. I visually observed the extruder and notice that when traveling between two separate parts, the extruder motor won't retract some times. The retraction works pretty well as long as it happens within a single part. That is why when I printed two sets of stringing test posts (4 posts total), there are almost no stringing within one set of posts, but lots of staging between the two separate sets. Again, the motor seems like it randomly fail to retract during travel between parts. If I print just a single part, retraction is almost flawless and very little stringing problems using the same temperature, filament and same cura profile. Thanks.

Here's a tosser; grab a copy of Prusa Slicer 2 and a profile for your printer and see if anything changes. It's a free program and won't screw up anything already in place, but will almost certainly create a different g-code. It's easier to try a second slicer than it is to wade through a g-code file looking for anomalies.

Thanks Fred. I'll give that a shot.