Apr 28

How to reduce stringing?


As this is my first foray into 3d printing, looking for some advice to help reduce the amount of stringing I'm getting when printing parts with spires, or multiple pieces in a single print. I've calibrated the extruder as best I can with the tools on hand, +/- 1mm extra per 100mm. Did PID calibration for hotend and bed and flashed those settings into the firmware. Bed is as level as possible with a warped build plate. Single extruder setup while I wait for missing components as well.


Tried with mostly default Cura settings. 205 print temp, 7.5mm retractions at 70mm/s, result was less than desirable with the building below. tons of stringing between smaller printing areas.


Tried increasing retraction speed to 100mm/s, distance to 10mm, turned off combing and set retraction minimum distance to 0 to try and force retractions everywhere. Also tried another spool of filament and dropped temps another 5 degrees. Stringing was even worse this time around.

Now I'm on a third spool of filament, just printing small stringing tests with two towers (https://www.thingiverse.com/thing:2219103).

Left to right are Cura defaults @190 degrees(7.5mm/60mm/s),

180 degrees with 10mm distance and 100mm/s speed

and then 170 degrees 10mm/100mm/s speed using slic3r instead in case it was a slicer problem. Extruder clicking and under-extrusions there, so definitely can't print that cold.

All three spools are https://filaments.ca/collections/1-75mm-3d-filaments/econofil-premium-pla brand, just removed from the vacuum sealed bags before printing. What am I doing wrong here? And how can I fix this, since it's ruining my bigger prints.



Apr 28

Did you enable the eeprom in Marlin? Otherwise you will need to manually edit Marlin and reload the code to the printer. i believe the M500 command will work but nothing gets stored accoss power cycles.

I didn't, I just edited the config files with the new values and uploaded them to the board.

Apr 29

The black tube is pushed all into the hot end, bottom out? Also you may want to put a clip under the black ring as these fail. That would cause the tube to move in/out with retractions and that means the filament is not retracted properly and you get strings.

Retraction of 4-5mm should be enough to reduce the hot end pressure.

As far as I'm aware it's flush. When I originally put the hotend together the tube wasn't cut at a perfect 90 degree angle and I had some leakage during my early prints. That hasn't happened since I recut it. I've got some tape on the bowden tube where it enters the coupling and I don't notice any movement when the filament is retracting.

Apr 30

@Dataris Remiel Try increasing the retraction length further to 7-9mm, also increasing the retraction speed should help too. You may also be able to decrease the length of the PTFE tube too. A combination of these things should remove all of the stringing.

i'd even be happy with that i haven't even put down a line yet


Just following up in case other people have similar issues. Had to replace the extruder side pneumatic coupler because of shredded teeth so it couldn't hold the PTFE tube anymore, and added some clips to keep it from slipping during retraction forces - and didn't realize you needed to give the tube a sharp tug back to really engage the teeth. I also shortened the PTFE tube about 4 inches, and modified the firmware so I could set retraction speed to 100mm/s - the default cap is 50mm/s. That dealt with most of the stringing but there was still a bit of blobbing, so I increased the coasting volume to 0.25mm^3 and that seems to have my prints about 98% stringing free and generally decent prints now. I probably didn't need to do all of these as the retraction firmware limit I only figured out after pretty much everything else had been attempted.

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