What the heck is "HT_MBL10", as seen in filament notes and the machine GCODE on printers with Nextruder
This is more an "idle curiosity" question than anything important. Looking at the start code for my XL I see the following M109 command which sets the extruder pre-heat temp prior to bed probing. Myself and others have discovered that the temp values here are too high which causes oozes which screws up first layer probing. Easy enough to fix, the command is a little complicated with a bunch of compound `if` statements but all that's really going on is setting that temp based on strings of letters that appear in the filament type.
Here's the command as it appears in the default machine code in the current release of PrusaSlicer when you select a Nextruder-equipped machine:
M109 T{initial_tool} S{((filament_notes[initial_tool]=~/.*HT_MBL10.*/) ? (first_layer_temperature[initial_tool] - 10) : (filament_type[initial_tool] == "PC" or filament_type[initial_tool] == "PA") ? (first_layer_temperature[initial_tool] - 25) : (filament_type[initial_tool] == "FLEX") ? 210 : (filament_type[initial_tool]=~/.*PET.*/) ? 175 : 170)} ; wait for temp
This checks the filament notes for the string HT_MBL10, and if found, subtracts 10 from the first layer temp. All of the remaining tests check the filament type instead of the notes.
Random thoughts
"MBL" suggests something about mesh bed leveling, "HT" might be "high temp", "10" might be "subtract 10"? Maybe?
Here's a link to GH showing several occurrences of this, including one filament definition:
[filament:Spectrum PETG HT100 @PG] inherits = Spectrum PETG HT100; *PETPG* filament_notes = "HT_MBL10" first_layer_temperature = 260 temperature = 260
My guess: Some filaments didn't test well with a warmup too far below the desired print temp so they're using this is a tag to mark those materials.