Odd flow rate issue after upgrade  

Odd flow rate issue after upgrade

Hello,

here is my primary issue with my Prusa mini:

when printing, the flow rate changes within the printed object from upper left to bottom right corner (on XY).

Background:

I always had intermittend problems with the extruder throughout the years but got ever more issues with only certain filaments I once was able to print in the past, causing clogs in the extruder or not being able to be loaded at all (others worked fine). I cant say what about the filament is the issue as diameter seemed OK but its mostly with brands like extrudr PLA NX-2, 3Djakes in house PLA, Eryone PLA and others.

So I decided to finally upgrade to a dual gear variant with a printables design ( https://www.printables.com/model/294169-prusa-mini-extruder-with-filament-sensor/files).

It was assembled and steps set as intended- When first loading with a known problematic PLA it couldn't load and just clicked in the extruder when the fast ramming happens (as seen here https://forum.prusa3d.com/forum/hardware-firmware-and-software-help/loud-noise-when-unloading-doesnt-unload/). This doesn't happen wtihout filament inserted and as I later saw when loading PETG it also worked fine.

I looked into adjusting the extruder stepper current but I couldn't find the parameter in the firmware source code as the structure nowadays seems to differ from the one in the old tutorial. Kinda frustrated I settled for updating to the newest firmware and just puttin on more lubricant and tried loading some PETG and it worked without issues. Heureka!

I calibrated the first layer (as I also upgraded to a super Pinda) and did a bed level test print where the strange phenomenon was slightly visible. Subsequently I went on to test the flow rate with a test I usually use for that. There it became apparent: in the bottom left and top right corner, flow rate was at optimum while in the other corners it diverged into opposit directions... wtf is going on? I printed a upsized version with 4 instead of 2 walls and after that two objects in sequence and the divergence happens within each single object.

I don't have a clue right now other than some issue with the board electronics? Let me know what you think is going on.