Improving Stringing during tool change
With the latest firmware (5.1.2) and PrusaSlicer (2.7.1), stringing is very much under control on my 2T XL (with the filament I have).
However, I was still having some amount of fuzzy stringing and unwanted blobs, but only during multi-tool printing.
I narrowed down the issue to the wipe tower and found this related video:
Since that video was made, I believe the pre-tool-change moves were changed so that the head returns to the wipe tower before getting parked. However, I found that the issue in the video (large Z move leaving a vertical blob) is still present, just now on the wipe tower. My observation is that depending on the filament, this can cause accumulation of filament on the nozzle and more blob to develop on the tower and elsewhere.
Starting with fully clean nozzles and well-behaved filament, it usually works fine. But with more stringy/sticky filament, it can turn into blobs quickly, first on the tower, then on the printed items and start coating the nozzle in picked-up filament.
Adding the "G1 Y360 E-1 F24000" move from the video in the Filament End G-code (which moves the tool horizontally before the big Z-move) seems to solve the problem.
The pics below show (1st pic) some blobs sticking out of the normal height of the tower and (2nd pic) the vertical blob due to the Z-move.
