My interpretation of/assumptions about (MIA) above Bambu Lab Support (BLS) response:
From the wiki (A1):
“The eddy current sensor above the hotend will detect whether the nozzle has made contact with the heatbed.”
BLS:
“This aim is to extrude a filament section against the hot end, so that the bed auto-leveling data is more accurate. The relatively large print area of the A1 requires better pre-tightening of the hot end”
MIA:
Not larger than the other Bambu printers but larger than the A1 Mini’s print area (which also uses the eddy current sensor for Z-homing/bed leveling).
Apparently more accurate bed leveling (‘contact’) data is more important for the A1 than the A1 mini (?) because of the larger print area.
The pre-tightening of the hot end is caused by putting pressure (with extruder) on cold filament. This can only be done while the filament is cold and stiff and not when it is hot and soft/molten.
BLS:
“which will not damage the gear after internal testing”
MIA:
While this is probably a clever way to achieve that the hot end stays under some pressure (so the Eddy-current sensor gets more accurate bed leveling data), in general for the extruder it is not advisable to try feeding filament through a cold hot end.
Every time I hear this ticking/grinding extruder sound, it feels unnatural and unhealthy to me. But apparently this is ‘normal’ for how the A1 works.