2. This is Polymaker PLA, fresh out of the dryer. So the cause is not wet filament. Also, I used a little bed glue, it is not an adhesive problem. I am printing with Prusa 0.4mm hardened nozzle and the Generic filament profile. All settings are default. These were going to be gridfinity bins.

Prusa Connect status is ONLINE. I have already reconnected to Prusa Connect, but nothing changed. Firmware is up to date

I have a model that is clogging my Core ONE+ nozzle. I have tried multiple models, brand new filaments and even changed the nozzle. I am pretty sure the issue is with too many retractions. The model has close to 5,000 retractions over 1 mm in height (from what I have seen in the .gcode file).

I have tried adjusting the filament overrides: Retraction Length = 0.8 mm, Retraction Speed = 10 mm/s, Minimum Travel After Retraction = 5 mm, Retract On Layer Change = Off. I can see that the generated .gcode file has fewer retractions (around 2,200), but the issue (clogging the hotend) still persists.

I must be missing something. Any suggestions?

Thanks,

Marian.

Printing an L shaped bracket that is experiencing pitting on one face/area only. The print quality around the rest of the print is great. Please see attached photos.

Printer/Settings:

Prusa MK3S+ (Latest Firmware 3.14.1)

Prusa Slicer 0.2mm Quality Settings (Version 2.9.5)

Thoroughly dried, new Geeetech black PETG (16+ hours in Sunlu S2 dryer at 65 degrees with venting to 15% humidity), 0.2mm layer height, 5 perimeters, 20% gyroid infill, 240 degrees print temp, 90 degrees bed temp, organic supports where needed. Fan speed 30-50%.

It is 85%-90%+ humidity/~16 degrees Celsius where I live (UK), but it has been dried in the dryer in a room with a dehumidifier.

Speed: 45mm/s perimeters, 25mm/s small/external perimeters.

Extrusion Multiplier and Linear Advance (0.05, vs Prusa default 0.08) are calibrated.

What I have tried to solve the problem:

Thoroughly dried the filament.

Checked Z seam is aligned (I used seam painting to force it into the desired corner)

I printed the first part and observed the pitting defects. I cleaned out extruder gears and tried again, with a marginal improvement.

Lots of researching!

I have ruled out the below, but I'm open minded about checking:

Filament is thoroughly dry - if it wasn't, I think I would get these pit marks all over the print

Partially clogged nozzle - if it was, I think I would get these pit marks all over the print

Confirm Z seam settings correct.

Possible clues:

Pit marks are only on this small perimeter section only

Pit marks are not present at the bottom and top 5mm of the print. Instead, pit marks are only present where the section is 'disconnected' from the rest of the bracket.

Possible retraction/deretraction/back pressure issue. Whilst users in the below links have experienced pitting due to mis-set retraction settings, they have all been on the Prusa Mini (bowden) and I'm hesitant to change them on my MK3S+ (direct drive) due to it's already much shower retraction compared to a Bowden machine.

The extruder idler tension screw was 0.5mm below flush. I have loosened it to 0.5mm above flush in line with Prusa documentation, but have not done a third print yet to test.

Helpful guides/others who have experienced similar issue:

Pitting guidance - https://www.reddit.com/r/FixMyPrint/comments/xpvu09/diagnosing_stringing_vs_branching_vs_pitting/

https://forum.prusa3d.com/forum/how-do-i-print-this-printing-help/issue-with-gaps-in-layers/

https://www.reddit.com/r/ender3/comments/104yckq/how_do_i_get_rid_of_these_pits_on_my_3d_prints/

https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-how-do-i-print-this-printing-help/tiny-holes-in-printed-walls/

https://forum.prusa3d.com/forum/postid/604692/

Request

I would be very grateful if anyone could offer suggestions, guidance, or similar experiences that they have had and possible solutions to this problem. Many thanks in advance!

J'ai cassé le connecteur de la sonde de température sur la carte du nextrudeur. J'en ai commandé une de rechange mais je n'arrive pas à trouver le mode d'emploi pour le remplacement de cette carte.

Merci pour votre aide.

1. PCTG - I love this stuff. Kind of expensive but more vendors are joining the game. Approaching PETG prices
2. Prusa PC-Blend -  a very nice functional filament when stiffness and high temp resistance is needed
3. igus i150 - Great for gears, a bit expensive. PPA is another option
4. ASA - for anything outdoors
5. PC-CF - the most accessible "engineering grade" filament for a Core One. Easy to print. 

Least Favorite/Avoid

1. POM (Delrin) - To be fair, this probably shouldn't be attempted on any printer. I created a whole topic on this filament: How to print POM (acetal Delrin) on a Core One and why it is hell-spawn. 
2. PPA-CF - This is just on the edge of printability. You can print it with a 290° nozzle but layer adhesion suffers unless you print it VERY slowly as in 2-3mm^3/s. Also it's extremely stiff and brittle so feeding into the Nextruder can be a challenge. I was only able to get the Nextruder to clamp onto it by removing the Bowden and top-feeding it directly
3. PPS-CF - Do not attempt, nozzle cannot reach the optimal 310°
4. PET-CF/GF (*) - It's possible to print these but just barely. Layer adhesion for the CF variants are poor at 290° and must be printed slowly.  Why I put an asterisk next to it? On my H2D it's by far the best functional filament I own. 
5. Prusa Ultraglow PLA - This stuff is so abrasive it will eat everything it touches. It'll print just fine, you will just be replacing everything that came in contact with this filament after 1 spool. I might pick up a "sacrificial" Ender 3 just to print it.