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Preheat & heat-soak

Engineering filaments — ABS, ASA, PA (nylon), PC — want a warm bed and a warm chamber before the first layer goes down, or they lift, warp, and crack. Bambu firmware has a wait-for-chamber G-code (M191), but it silently ignores it on the models BamDude drives, so there's nothing on the printer side that holds the job back until the enclosure is up to temperature.

BamDude's preheat stage fills that gap. When enabled, the scheduler heats the bed (and, on chamber-equipped printers, the chamber) and holds at temperature before the queued print starts — running the soak while the printer is otherwise idle, in the window between the file uploading over FTP and the print actually starting.

It's off by default — existing installs see no change until you turn it on.

How it works

The stage runs on the idle printer, right before dispatch, and resolves everything per print:

  1. Should it run? The per-print override decides — off skips, on forces it on, inherit (the default) follows the global Preheat & Heat Soak toggle.
  2. Bed target is read from the print file's own metadata. If the file carries no bed temperature, preheat is skipped for that print.
  3. Chamber target is worked out from the loaded AMS filament types: BamDude looks up each loaded slot's type in the chamber-target map and takes the hottest across all loaded slots — so a mixed PA + PLA job soaks for the PA. A target of 0 skips the chamber phase but still runs the bed phase and the soak.
  4. Hardware tier decides how the chamber phase behaves (see below).
  5. Wait, then soak. BamDude waits for the bed (and, where possible, the chamber) to reach target — up to the max-wait cap — then holds at temperature for the soak duration. Both loops abort cleanly if you cancel the queued print mid-soak.
graph LR
    A[Job about to dispatch] --> B{Preheat on?}
    B -- no --> Z[Start print]
    B -- yes --> C[Heat bed to file target]
    C --> D{Chamber target > 0?}
    D -- yes --> E[Heat / wait per hardware tier]
    D -- no --> F[Bed only]
    E --> G[Soak at temperature]
    F --> G
    G --> Z

Per-filament chamber-target map

The chamber target for a print is derived from the loaded filament types. The built-in map ships these defaults (°C), fully editable under Settings → Printing → Preheat & Heat Soak:

Filament Chamber target
PLA 0 °C
PETG 0 °C
PETG-CF 40 °C
ABS 45 °C
ASA 45 °C
PA 50 °C
PC 50 °C
PC-FR 50 °C
PA-CF 55 °C
TPU 0 °C
PVA 0 °C
Other / unmapped (default) 0 °C
  • 0 means "no chamber phase" — commodity filaments (PLA, PETG, TPU, PVA) derive 0, so a PLA-only print skips the chamber wait entirely and just does the bed + soak.
  • The highest target across loaded slots wins. Load PA in slot 1 and PLA in slot 2 and the print soaks to PA's 50 °C — the engineering filament's requirement is binding.
  • Each value is capped at 60 °C in the editor. Reset the whole map to the shipped defaults with one click.

Where the defaults come from

These are the chamber-temperature recommendations Bambu Studio ships for the matching filament profile. They're a sensible starting point, not a hard rule — tune them for your enclosure, ambient temperature, and part geometry.

Three hardware tiers

The chamber phase behaves differently depending on what the printer physically has. BamDude picks the right tier automatically from the model:

Tier Models What happens
Active chamber heater X1E, X2D, H2C, H2D, H2D Pro, H2S Sends M141 to drive the chamber heater to target, then waits for the chamber sensor to reach it (or the max-wait cap).
Chamber sensor only X1, X1C, P2S No active heater — the bed warms the chamber by radiation. BamDude waits for the chamber sensor to rise toward target, falling through on the max-wait timeout (radiant warm-up can take 15–30 minutes).
No chamber sensor P1S, P1P, A1, A1 Mini No chamber reading at all — BamDude heats the bed and holds on the soak timer alone.

The bed phase runs on every model

Only the chamber phase is model-gated. The bed always preheats and the soak always runs, so even a sensorless P1S gets a properly heat-soaked bed before an ABS print — the enclosure warms passively while the timer counts down.

Airduct flap

On models with a cooling/heating airduct flap — P2S, X2D, H2C, H2D, H2D Pro, H2S — BamDude flips the flap to match the target before energising the chamber: heating mode (closing the exhaust) when there's a chamber target, cooling otherwise. Bambu firmware won't switch the flap for you, and the default cooling position actively vents the chamber and fights the heater. The flip is idempotent — it's skipped when the flap is already where it needs to be.

Settings

Settings → Printing → Preheat & Heat Soak.

Setting Default Range What it does
Enable preheat & soak Off — Master toggle. When off, queued prints dispatch immediately. Each queue item can still override per print.
Per-filament chamber target (bundled map above) 0–60 °C per row The editable filament → chamber-target map.
Max wait (seconds) 900 (15 min) 60–3600 Cap on the warm-up phase before falling through to the soak — stops a slow radiant warm-up from stalling the queue forever.
Soak (seconds) 300 (5 min) 0–1800 Hold time at temperature after the target is reached (or after max-wait elapses). 0 disables the soak.

Per-print override

The Print dialog's options carry a Preheat control so you can flip the decision for one print without touching the global setting:

Option Effect
Inherit (default) Follow the global Settings → Printing toggle.
On Force the stage on for this print even if the global toggle is off.
Off Skip the stage for this print even if the global toggle is on.

When it isn't set to Off, an optional Chamber target override field lets you type an explicit chamber temperature (°C) for this print. Leave it blank to use the filament-derived default; an explicit 0 means "bed and soak, but no chamber phase" even if the loaded filament would otherwise want one.

Permissions

Action Permission
Configure the global preheat map + timings settings:update (Administrators)
Set the per-print override on a job queue:create / printers:control — whatever you'd already need to dispatch that print

Caveats

  • No bed temperature, no preheat. The bed target comes from the print file's metadata. A file with no bed temperature (rare) skips the stage entirely.
  • Best-effort throughout. A dropped printer, a refused M141, or a missing sensor reading logs and continues — the normal upload + start path always runs afterward. Preheat never blocks a print from starting; it only delays it.
  • The soak eats into throughput. A 15-minute radiant warm-up plus a 5-minute soak is 20 minutes the printer isn't printing. That's the point for engineering filaments, but keep the max-wait sane on a busy farm.
  • External-spool prints derive no chamber target. If a print runs off an external spool with no AMS filament data, the chamber phase short-circuits (target 0) and only the bed + soak run — use the per-print chamber override if you need a chamber soak there.