Prusa Stringing  

RE: Prusa Stringing

A few quick notes:

• PETG is prone to absorbing moisture. Try drying your spool or using another to see if the stringing is still an issue.
• Even slight over-extrusion with PETG can increase stringing. Prusa has a guide on one method of calibrating your extrusion multiplier for each filament.
• Disabling z-lift (Printer Settings->Extruder 1->Retraction-Lift Z) can reduce stringing but possibly cause issues with scarring on horizontal surfaces.
• Unlikely, but a damaged nozzle can contribute to stringing. Try another filament to see if you still have issues.

I'm using a Mk3, so hopefully others with more experience with PETG on a Mini will chime in with more suggestions.

RE: Prusa Stringing

just some ideas:

- using the right settings in Prusaslicer in reference to your nozzle diameter?

- updated to latest firmware?

I switched my Mini completely to PETG, without any trouble so far. 

RE: Prusa Stringing

Update: I contacted Prusa Support and tried a load of other things:

• Switched to using the USB rather than Octoprint
• Updated to latest 4.2 firmware
• Tried Brand new Prusament PETG White
• Tried generic PLA

All of these were for nought. The final recommendation is to move the print head up as it might be too far down, which is what I will be doing this evening.

RE: Prusa Stringing

Pics of the Nozzle. Anyone got a picture of theres so I can see a comparison of the distance between the nozzle and the heatsink?

Brand new White PETG:

RE: Prusa Stringing

why lift Z make better in string problem?

RE: Prusa Stringing

This is very interesting. I'm having the same issue with my Mini. My first Benchy printed very well, but it had loads of stringing printed with ESUN PLA+.

I have attached pictures of my stringing tests in SunLu PETG and a picture of my print head to show the distances. I'm still looking for a solution to this. I think my next action will be to try drying the filament, although the filament I did try was brand new fresh out of the box??

If anyone has more suggestions I'd like to hear.

RE: Prusa Stringing

@magicpracticalflame

"Switched to using the USB rather than Octoprint" hard to imagine how that could affect stringing.

RE: Prusa Stringing

There have been last issues with Octoprint plugins that have caused stringing and other defects. Printing directly off SD is a good diagnostic check. If that prints well, try safe mode or eliminate plugins. Doesn't sound like it was the problem in this case, but it's a good thing to be aware of. I had issues with the Display layer progress plugin about a year ago.

RE: Prusa Stringing

@bobstro

Absolutly agree that OctoPrint can cause all sorts of errors but stringing?

RE: Prusa Stringing

@paul-c30

Glad I'm not the only one with the issue.

Update

Today I have replaced the nozzle and followed the instructions to push UP the hotend block. When I undid the feed tube I noticed that the PTFE tube inside the heatsink was recessed slightly, rather than poking up past the heatsink. I pushed the heatblock up by undoing the 3 screws on the side of the heatsink slightly so that the PTFE tube was poking about 2mm above the heatsink. Calibrated with the final layer and remembering to adjust the probe to be the right height.

Put in my brand new Prusament PETG and did the exact same stringing test with stock defaults. While the stringing was there, it wasn't anywhere near as bad. I lowered the temperature on the fly halfway through to 240C which improved things massively. I'm now going back to square 1 and testing all the settings again. @paul-c30 I would try pushing the heatblock up as yours is the same distance mine was.

RE: Prusa Stringing

In regards to Octopint, I noticed no difference with Octoprint vs without. The only thing that would change with stringing is turning on Octolapse which MASSIVELY increased stringing.

RE: Prusa Stringing

Hi magicpracticalflame, many thanks for the update, I will try and adjust the PTFE tube in my hotend and let you know the results.

RE: Prusa Stringing

Hi All,

So I replaced the PTFE tube on my mini to see if I could resolve the stringing problem. This only marginally improved things. 

I then tried drying out my filament ( PLA-X HobbyKing ) in a domestic oven at about 50 deg C for 4 hours. The prints I get are now significantly improved. The stinging in minimal even on the Prusa Retraction setting of 3.2mm, in fact it could be the best of my tests.

I've attached a picture of the results  of  my before and after. You can also see the surface finish is also a lot better.   

I will now try my PETG and see if that improves.

RE: Prusa Stringing

I used the new Calibration tool ( Retraction Tuning ) test from Teaching Tech which can be found here :-

https://teachingtechyt.github.io/calibration.html

You can dial in various retractions at each stage of printing the tower.

RE: Prusa Stringing

Posted by: @towlerg

@bobstro

Absolutly agree that OctoPrint can cause all sorts of errors but stringing?

Oh yes. 🙂 If the OctoPrint plugin is misconfigured for example, it will introduce all sorts of movements that cause stringing.

RE: Prusa Stringing

@bobstro

"If the OctoPrint plugin is misconfigured for example," typo? perhaps you meant OctoLapse?

RE: Prusa Stringing

@paul-c30

thank you

RE: Prusa Stringing

@paul-c30

this look great

RE: Prusa Stringing

Posted by: @towlerg

[...] "If the OctoPrint plugin is misconfigured for example," typo? perhaps you meant OctoLapse?

The OctoLapse plugin (as one example) for OctoPrint to be specific. If misconfigured, it can create a mess. The DisplayLayerProgress plugin was another source of print quality issues recently due to a bug. Any slowdowns on the RPi itself (e.g. throttling, crashes) can also cause odd timing-related problems. The point being that anybody using OctoPrint should mention as much when describing print problems and troubleshoot (run OctoPrint in safe mode, test plugins) before tearing their printer apart.