After years of clean prints, suddenly terrible overhangs and bridging
After several years af great printing with my MINI using eSun PLA+, overhangs and bridges have started printing absolutely terrible.
I have not installed any hardware modifications. All parts are stock from the 2021 MINI kit. Tried printing with .20 QUALITY .20 SPEED .15 SPEED on the stock "Esun PLA" slicer settings.
I hadn't changed any settings from the successful prints, it is using the same gcode even. As soon as the filament leaves the nozzle it droops down and turns into spaghetti. This makes supports impossible to remove cleanly, as the first layer above the supports will droop down and fuse into the supports.
Bumping the bridging speed up to 60 mm/s and decreasing flow ratio to .2 was able to bridge a 20mm gap successfully, but overhangs were still failing for the same reasons. So the bridging speed tweaks were not able to fix the root problem.
I worked with support on this for many many hours, we tried
* New filament
* Changing and tuning all manner of bridging parameters, overhang speed, fan speed / cooling,
* Upgrading printer firmware and slicer
* Measuring PTFE tube
* Removing hotend and reapplying new thermal paste
* Verifying hotend and bed temperatures (same as when I was making successful prints)
Failed bridging (default settings)
Failed overhang (default settings)
2 months ago with same exact default settings, successful overhang with no supports used
Underside of failed overhangs
RE: After years of clean prints, suddenly terrible overhangs and bridging
More failure modes,
Some straight walls on edge of print are drooping into itself. This is above about a cm of support material.
More consistently poor bridging, suspended on both ends, length about 1cm.
I believe the hotend temperature is accurate. As part of diagnostics with support I reseated the thermistor and repasted the heatblock. Furthermore, I reduced the print temperature in steps of 5C and noted that the steps and effects on filament extrusion were consistent to when it was printing properly.
RE:
Any firmware/software updates?
Also make sure the fan that blows at the nozzle does not have any blocked path (the fan on the back of the X axis and check the tunnel which guides the air flow), because you have a typical hanging bridge which means there is not enough of cooling when printing, thus the filament is hot and bends due to gravity, and it should be cooled so that it becomes stiff so it does not hang.
See my GitHub and printables.com for some 3d stuff that you may like.
Agreed. This does look like a cooling issue.
In addition to @_kaszpir_'s suggestions make sure the fan is clean, that there is no fine stringing clogging the hub and maybe try a single drop of oil on the hub to free it.
Cheerio,
RE: After years of clean prints, suddenly terrible overhangs and bridging
Thanks for the suggestions.
I was running the same 4.2.1 firmware since I originally set up the printer, and first encountered this cooling issue. I upgraded to 6.0.2 with no effect.
Print fan, completely clean, likewise tunnel is clean Fan is spinning freely.
Video of print fan with audio, blowing at correct part of print head.
Video of printing bridge, the fan seems to be blowing the filament down and out (direction of print fan airflow).
RE: After years of clean prints, suddenly terrible overhangs and bridging
Did you replace the hot end PTFE tube? I just buy a pack and replace if I even think there is an issue. Even a tiny burr can allow filament to leak and cause a clog. What does a cold pull look like?
Regards,
Mark
RE:
I did not replace the tube, but I did inspect it, it was in good condition and smooth on the inside. And I did reseat the hotend according to the manual, which should be providing the proper force and spacing on the tube.
Here is a cold pull.
