Slicing guide

Choose a path

There are two ways to get a printable file.

Path A: slice in your slicer's GUI, then hand the file to the server. Slice, check the preview, and export. Then upload a .gcode file with upload_gcode, or print a sliced Bambu .3mf with print_3mf. You see exactly what will print, so this is the most predictable path.

Model ──► slicer GUI ──► sliced .gcode / .gcode.3mf ──► upload_gcode or print_3mf
          slice + preview + export

Path B: let the server run your slicer's command line. slice_stl runs the configured slicer and returns the output path. Your agent can then check temperatures with confirm_temperatures and upload the result. This is what makes "edit this model and print it" work end to end, but it depends on your installed slicer and profiles.

STL / 3MF ──► slice_stl ──► slicer CLI ──► .gcode (or sliced .3mf for Bambu) ──► upload_gcode / print_3mf

Printing a file that is already sliced needs no slicer on the MCP host. Either way, every print start goes through the print safety gate, including a human confirmation.

Slicer types and aliases

Set SLICER_TYPE in the server environment, or pass slicer_type to a tool.

SLICER_TYPE	Slicer	Output	Also accepted
prusaslicer	PrusaSlicer	G-code	prusa
slic3r	Slic3r	G-code
orcaslicer	OrcaSlicer	G-code, or a sliced Bambu .3mf when the call passes bambu_model	orca, orca-slicer
cura	CuraEngine	G-code	curaengine
orcaslicer-bambulab	FULU OrcaSlicer-bambulab	Sliced Bambu .3mf	fulu-orca, fulu_orca, orca-studio, orca_studio, orcastudio, orca-bambulab, orca_bambulab, orcaslicer_bambulab
bambustudio	Bambu Studio	Sliced Bambu .3mf	bambu-studio, bambu_studio

The environment variable accepts every alias. A tool's slicer_type argument accepts the canonical names plus fulu_orca, fulu-orca, orca-studio, and orca_bambulab.

When SLICER_TYPE is not set, the server uses orcaslicer-bambulab if PRINTER_TYPE=bambu, and prusaslicer otherwise.

Where the server looks for the slicer

SLICER_PATH always wins. Without it:

• FULU OrcaSlicer-bambulab uses FULU_ORCA_PATH, ORCASLICER_BAMBULAB_PATH, or ORCA_SLICER_BAMBULAB_PATH, then the first existing path among /Applications/OrcaSlicer.app/Contents/MacOS/OrcaSlicer, /Applications/Orca Studio.app/Contents/MacOS/OrcaSlicer, /Applications/OrcaStudio.app/Contents/MacOS/OrcaStudio, /usr/local/bin/orcaslicer, and /usr/bin/orcaslicer, then orcaslicer on PATH.
• Bambu Studio tries /Applications/BambuStudio.app/Contents/MacOS/BambuStudio, /Applications/Bambu Studio.app/Contents/MacOS/BambuStudio, /usr/local/bin/bambustudio, and /usr/bin/bambustudio, then bambustudio on PATH.
• PrusaSlicer, Slic3r, OrcaSlicer, and CuraEngine need SLICER_PATH.

A per-call slicer_path is refused unless MCP_ALLOW_EXECUTABLE_ARG=1; see executable settings. Slicer runs time out after SLICER_TIMEOUT_MS (10 minutes by default).

Profiles

SLICER_PROFILE (or the slicer_profile argument) and FILAMENT_PROFILE (or filament_profile) mean different things for each slicer:

Slicer	SLICER_PROFILE	Filament profile
PrusaSlicer, Slic3r	One config file exported from the slicer (File > Export > Export Config), containing printer, print, and filament settings	Not used; include filament settings in the exported config
Generic OrcaSlicer (no bambu_model)	Machine and process JSON files separated by ;, optionally followed by a filament file (see below)	Loaded with --load-filaments
CuraEngine	A Cura definition JSON	Not used
Bambu Studio, FULU OrcaSlicer-bambulab, or OrcaSlicer with bambu_model	One process profile only. The machine preset always comes from the printer model and nozzle; a machine;process list is rejected with instructions	;-separated, in slot order, loaded with --load-filaments

For generic OrcaSlicer, a filament file can ride along in the profile setting after a pipe character:

SLICER_PROFILE=/path/to/machine.json;/path/to/process.json|/path/to/filament.json

Generic OrcaSlicer writes plate_1.gcode; the server renames it after the input model and returns that path. Do not use this form for Bambu Lab slicing: pass bambu_model (or use Bambu Studio or FULU OrcaSlicer-bambulab) and give only a process profile.

Bambu-compatible slicing

Bambu Studio, FULU OrcaSlicer-bambulab, and OrcaSlicer with bambu_model produce a sliced Bambu .3mf. Before the slicer runs, the server prepares the profiles itself:

1. Machine preset. It takes the model from bambu_model (or BAMBU_MODEL, asked for through elicitation when missing) and the nozzle from nozzle_diameter (or NOZZLE_DIAMETER, default 0.4), and finds the exact <model> <diameter> nozzle machine preset, such as Bambu Lab P1S 0.4 nozzle, in the selected installation's BBL profile tree. The tree is found from SLICER_PATH, or set with BAMBU_PROFILES_ROOT for AppImages and non-standard installs. A preset is never borrowed from another installation.
2. Resolution. inherits and include chains are flattened, and the model's cli_config.json entry is validated. Custom process and filament parents are looked up in BAMBU_SLICER_PROFILE_DIRS (default: the slicers' user system/BBL directories), never machine presets.
3. Process and filaments. slicer_profile, a template, or BAMBU_TEMPLATE_3MF_PATH supplies process settings. Machine settings carried by process, filament, or template files are dropped, so they cannot replace the selected preset's start G-code.
4. Checks. Missing presets, wrong nozzle sizes, missing parents or includes, cycles, malformed profiles, missing process or filament files, and machine/process lists in slicer_profile all stop before the slicer runs.
5. Output. The result must contain a nonempty Metadata/plate_<n>.gcode. A checksum-only archive, missing output, or a stale file from an earlier run is an error. Slicer failures report the exit code or signal, whether it timed out, the tails of stdout and stderr, and slicing-specific suggestions.

Slicing accepts p1s, p1p, p2s, x1c, x1e, a1, a1mini, h2d, h2s, and h2c when the installed slicer has that preset. Printing accepts p1s, p1p, x1c, x1e, a1, a1mini, and h2d.

slice_stl and slice_with_template also take bed_type, nozzle_type, load_filaments, load_filament_ids, filament_colours, template selection, and the Bambu CLI placement and transform options (orient, arrange, ensure_on_bed, repetitions, clone_objects, skip_objects, slice_plate, scale, rotate, rotate_x, rotate_y, uptodate, min_save, skip_modified_gcodes, enable_timelapse, allow_mix_temp). See the slicing tools reference.

Evidence. Bambu Studio 02.01.01.52 sliced a P1S 0.4 nozzle job through this path, including a 9.7 MB refitted phone-case STL in Bambu TPU 95A HF (230 °C nozzle, 35 °C plate, about 1 h 38 min and 21 g); see the Blender guide's worked example. Before this change, Bambu Studio rejected the raw inherited P1S preset with exit 239 ("process not compatible with printer"). Other slicer versions and models have not been tested here.

Slicing templates

A template is a saved .3mf, .json, or .config file whose slicer settings are reused as the process profile. Templates live in a local registry, BAMBU_TEMPLATE_DIR (default ~/Sync/bambu/templates); every tool also accepts a template_dir override.

• save_template copies a file into the registry under a name (default: the source filename).
• list_templates lists the saved templates.
• get_slice_settings shows a template's or file's layer height, infill, walls, supports, brim, bed, printer, and filaments without slicing.
• slice_with_template slices with a named template. The machine preset still comes from bambu_model and nozzle_diameter, and an explicit slicer_profile in the call overrides the template.

slice_stl accepts template_3mf_path or template_name too, and uses BAMBU_TEMPLATE_3MF_PATH as a default template when set.

Printing what you sliced

• G-code (any backend): upload_gcode with gcode_path and print: true inspects the exact file, checks the printer, asks a human to confirm, and starts it. Without print, the file is only uploaded. Printing needs a declared material: ; filament_type in the G-code or the material argument.
• Sliced Bambu .3mf: print_3mf inspects the selected plate, compares it with a fresh printer report, asks a human to confirm, then uploads the project over FTPS and starts it over MQTT. It works only with PRINTER_TYPE=bambu, and bed_type must match the plate's bed metadata. The job's nozzle type must also match the printer's reported nozzle: Bambu machine presets assume the stock nozzle (stainless steel on P1S, P1P, and A1; hardened steel on X1C and X1E), so if you upgraded yours, slice with nozzle_type (or set BAMBU_NOZZLE_TYPE). After the print command, the server watches the printer's reports and says whether it started, stayed silent, or was refused by the firmware.
• Check first: confirm_temperatures reports every heater target in a G-code file (S and R forms, tool-addressed, RepRapFirmware G10/M568, and Klipper SET_HEATER_TEMPERATURE). An expected temperature matches only when it equals the file's highest target, returned as peak. It does not change the file.

print_3mf auto-slicing

If a .3mf passed to print_3mf has no plate G-code, the server tries to slice it first with the configured Bambu-compatible slicer and your printer model's machine preset. If slicing fails, or the selected plate still has no G-code, print_3mf stops with an error and never uploads the original project. Export a sliced plate from the GUI (Path A) for the most predictable result.

Layer height, temperatures, and other slicer settings are baked into the sliced file. Change them in the slicer and slice again; print_3mf accepts layer_height, nozzle_temperature, bed_temperature, and support_enabled but does not apply them.

process_and_print_stl

This one-call pipeline extends the model's base (extension_inches, converted at 25.4 mm per inch), slices it, and prints it through the same checked gate as upload_gcode and print_3mf, including the human confirmation. If you pass extruder_temp or bed_temp, each must equal the sliced job's highest target (S and R forms, every tool); otherwise nothing is uploaded. Pass material when the sliced G-code has no filament_type metadata. For a Bambu printer with a Bambu-compatible slicer, the sliced .3mf goes through the print_3mf checks.

Use the separate slice_stl, confirm_temperatures, and upload_gcode steps when you want to inspect the sliced file before the print is offered for confirmation.

Slicing in Docker

The Docker image does not include a slicer, and a slicer installed on the host generally cannot run inside the container because of library and OS differences. To slice in a container, build a derived image that installs a Linux build of your slicer, set SLICER_PATH to its path inside the container, and set BAMBU_PROFILES_ROOT if its profile tree is not found automatically. See Running with Docker.

Troubleshooting

• The slicer opens its GUI or hangs: some slicers fall back to the GUI when the command line is incomplete. Configure a complete SLICER_PROFILE and check that SLICER_PATH points at the executable, not the app bundle folder.
• PrusaSlicer ignores my settings: SLICER_PROFILE must be a single exported config file, not a folder of profiles.
• Bambu slicing cannot find the machine preset: point SLICER_PATH at the executable inside a full Bambu Studio, OrcaSlicer, or FULU OrcaSlicer-bambulab install that includes your model and nozzle, or set BAMBU_PROFILES_ROOT to its profile tree. SLICER_PROFILE cannot supply a machine preset.
• slicer_profile is rejected for listing a machine preset: on the Bambu-compatible path, pass only the process profile. The machine preset comes from bambu_model and nozzle_diameter.
• A custom process or filament profile's parent is missing: add the directory holding it to BAMBU_SLICER_PROFILE_DIRS.
• The slice fails with an exit code: read the reported output tails and suggestions. Bambu Studio's exit 239 means the process profile does not fit the printer preset.
• FULU OrcaSlicer-bambulab CLI crashes on macOS: see current FULU status; Bambu Studio's CLI is a known-good alternative.
• Long slices time out: raise SLICER_TIMEOUT_MS.