Print starts to print perfect firt layer and the stops extruding  

Update: tested again after cleaning feeder gears

So I opened it up again and cleaned the feeder gears they had material build up embedded in the recesses of the gear. 

just completed a successful 3x3

https://youtube.com/shorts/SrACCibeS8E?si=fZhxy4Wph8phqEm6

Going to start the 5hr print  and will update  

RE:

So I printed a 5hr print - and believe it or not it lasted up to the very last few mins where you can see imperfections happening. Most likely where there are more retractions - So this time I decided to check the set screw on the extruder drive gear.

So first to diagnose - I heated up the block - and did an unload - I heard the motor but the gear did not spin as I inspected it through the idler tension door  - so not sure if the shaft spun in the gear - or if there is some protection in the extruder motor (or if the extruder motor was bad) - anyway - the filament did not unload until I pulled on it - now there was possibly still a jam in the heat-break as when I manually pushed on the filament it did not budge as easily so heat creep may still be a factor here. When I checked the set screw - it wasn't super tight, and came loose easily - was that enough to cause the issue? who know.  but when manually spinning the shaft by turning the gear - it did spin around the shaft but there was some noticeable resistance - so not sure if the extruder motor may be bad. so I reassembled and started a 3x3 calibration - about 15 mins into it - I start hearing clicking - so I tighten the tension spring screw and it stops and filament is still being extruded. I am testing another 5hr print again and this should be the final test - I still think I am getting heat creep - I order a new motor, block, thermistor and heating core and plan on replacing all this if my final test does not work.

Update: it failed again

I guess it is heat creep - it failed again:

https://youtube.com/shorts/vP_RqYcBXFo?feature=share

RE: Print starts to print perfect firt layer and the stops extruding

I got everything tuned pretty well (or so I thought), which included tuning the E-steps (945 which is 10x the original value of 93, however normal for this BIQU H2), my home position, changing the retraction setting, setting my K-factor for linear advance, tuning PID, etc. I flashed these settings into a custom Jyers Marlin firmware. Everything was working fine, and I was starting to get some really high-quality calibration tests, so I then began tuning my slicer profile. retro bowl college

RE:

My suggestions/checks:

1) Ensure your filament from the extruder to the spool has very low friction. I had a similar issue, just to discovered that to unspool a piece of filament I (and the extruder) had to apply a considerable force (e.g. over 700 gr) in order to pull the filament and cause the spool to roll. Basically the motor forced too much trying to pull the filament, and the filament was grasped and eroded on the extruder gear, and then when it was too thin to be grasped it shifted and blocked there.

2) Check the screw tension of the extruder gear. Should not be too loose or too tight.

3) Clean the nozzle using a cold pull and a 0.4 needle.

4) The internal of the brass nozzle could have small encrustations that block the flow, so it seems free but id cause a low material flow and the underflow.
     In case of doubts replace the nozzle.

5) Verify that the hotend/nozzle/fan  positions are correct and that the heat do not go where it should not, causing a clog. Better to take a photo of the nozzle/extruder with an infrared camera to verify the hot zones.

Regards