A friend of mine discovered the recent change of start up gcode quite interesting:
;==== set airduct mode ====
{if (overall_chamber_temperature >= 40)}
M145 P1 ; set airduct mode to heating mode for heating
M106 P2 S0 ; turn off auxiliary fan
M106 P3 S0 ; turn off chamber fan
{else}
M145 P0 ; set airduct mode to cooling mode for cooling
M106 P2 S178 ; turn on auxiliary fan for cooling
M106 P3 S127 ; turn on chamber fan for cooling
M140 S0 ; stop heatbed from heating
M1002 gcode_claim_action : 29
M191 S0 ; wait for chamber temp
M106 P2 S0 ; turn off auxiliary fan
{if (min_vitrification_temperature <= 50)}
{if (nozzle_diameter == 0.2)}
M142 P1 R30 S35 T40 U0.3 V0.5 W0.8 O40 ; set PLA/TPU ND0.2 chamber autocooling
{else}
M142 P1 R30 S40 T45 U0.3 V0.5 W0.8 O45; set PLA/TPU ND0.4 chamber autocooling
{endif}
{else}
{if (!is_all_bbl_filament)}
M142 P1 R35 S40 T45 U0.3 V0.5 W0.8 O45 L1 ; set third-party PETG chamber autocooling
{else}
{if (nozzle_diameter == 0.2)}
M142 P1 R35 S45 T50 U0.3 V0.5 W0.8 O50 L1 ; set PETG ND0.2 chamber autocooling
{else}
M142 P1 R35 S50 T55 U0.3 V0.5 W0.8 O55 L1 ; set PETG ND0.4 chamber autocooling
{endif}
{endif}
{endif}
{endif}
;==== set airduct mode ====
Look at the M142 parts. It sets the chamber cooling strategy.
Take this line as example:
**M142 P1 R35 S50 T55 U0.3 V0.5 W0.8 O55 L1 ; set PETG ND0.4 chamber **
R35= if temp is higher than 35C → triggers U0.3 = Chamber exhaust fan at 30%
S50= if temp is higher than 50C → triggers V0.5 = Chamber exhaust fan at 50%
T55= if temp is higher than 55C → triggers W0.8 = Chamber exhaust fan at 80%
O55 L1 is likely the trigger of high chamber temperature warning message. It might pop up a HMS message if the chamber temperature exceeds 55C for this material.
In short:
Bambu’s new strategy is interesting and likely result in a better print result for Bambu PETG filaments. But you can adjust the values yourself to reduce or increase the chamber cooling if you want. You can even disable exhaust by setting U to U0.0.
From the naming of RST and UVW, I guess that’s all we have for the temperature curves (3 points, RST → UVW)