Defective .4mm Hardened Hotend?
On my P1S, I recently decided to upgrade my stock .4mm hotened to the Bambu hardened steel variety.
Before this, my prints were really dialed in and honestly couldn't tell you the last time I had one go bad.
I print a lot of clay cutters, clay cutters, and other clay tools for my wife as well as a lot of organizational type things (gridfinity, multiboard, etc)
As soon as I swapped out the hotend (the entire assembly) I started having issues. Infill turning into spaghetti, bed adhesion issues, surface layers turning into balls of goo .... all of it.
Using Claude, I spent days troubleshooting. Filament settings, drying filament, printer settings, you name it.
Ultimately, I got to the point where I decided to swap into my .6mm stainless hotend...just to see. Perfect prints from the first one. Ok, let's go back to .4....nope, same issues. Purges, cold pulls, disassembled the entire printhead, cleaned and reassembled, and at that point I couldn't even get a successful purge strip and 1st layer.
Ok, let's try the .2... Perfect prints.
This thing is defective, right? It has to be. I ruled out everything else physical. I reverted to stock profiles. I used a bigger and a smaller hotend Assembly...it has to be the hotend itself. Right?
EDIT: anticipating...
Yes, I washed the plate with soap and water. Yes, I ran calibration. Flow calibration as well and even it failed. Yes, I changed the setting for the nozzle on the printer Yes, I had the right plate selected in Bambu Studio Yes, I did Auto Bed Levelling.
Taking the hotend/.4mm nozzle out of the equation solves the problem.