Cura Intermittent Retraction Causing Stringing Problem During Print

[twnismo 0]

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

[twnismo 0]

Hi guys, any ideas would be appreciated. This is so frustrating and limits me to print one object at a time. Thanks.

[GregValiant 1,145]

No M207, M208, M209 in the gcode?  They would be setting firmware retraction.

PLA is fairly fresh?  Water in the PLA can make it soupy.  The low printing temperature may point to that.  Is that silky PLA?  I've had trouble with that as well.  It seems to soak up water faster than regular PLA (but I'm in a humid environment).

Increase the Max Retraction Count up to 100.  This falls under "can't hurt".

That's about it for me.  

 

 

 

 

[twnismo 0]

Hi Greg, thanks for the response. I guess I didn't write my original question clearly. I've proven that its not the material or temperature. The actual extruder motor won't retract at random times during travel between two separate parts of the same print. Sometimes it retracts other times it won't over the same travel path. Retraction is mostly perfect if within an individual part. Problem mostly occurs during travel between two separate parts. That's why in picture #3, the two sets of stringing test posts, there are no stringing within one set, but lots of stringing between the separate sets. Thanks.

 

 

[GregValiant 1,145]

Either the Z-hops are in the Gcode but aren't being acted on by the printer, or they aren't in the Gcode.

Post a gcode file that shows the problem and post that STL as well.  I have a macro for Excel that I can tweak to point to where retractions should happen but maybe aren't.  I'll slice the STL later and see how things go using my generic profile.

Edited January 13, 2021 by GregValiant

[tinkergnome 926]

 

On 1/6/2021 at 8:00 AM, twnismo said:

The settings I'm using which provided a slightly better results in the pictures is below.

 

10 retractions (at max.) for 6mm length of filament is way too low... (even for 1.75mm filament).

Allow at least 10 retractions per millimeter - that's a more reasonable ratio.

 

Have you tried the suggestion from @GregValiant?

 

On 1/12/2021 at 1:07 AM, GregValiant said:

Increase the Max Retraction Count up to 100.  This falls under "can't hurt".

 

 

And always check the preview for travel moves without retraction. No need to actually print it, if you already see dark blue lines in the preview. Choose "Line Type" and enable "Travels".

Travel lines in light blue are with retract, the darker ones are without retract (like in this example):

 

[GregValiant 1,145]

Thanks @tinkergnome.  I'm Crippled by Compatibility Mode.