OrcaSlicer MCP

An MCP server that gives Claude (or any MCP client) the full FDM pipeline: slice models headlessly with OrcaSlicer, manage presets, analyze G-code, and control your printer over the local network — Klipper, OctoPrint, Prusa, Duet, Elegoo, or Bambu.

Ask your assistant to "slice this STL with my draft profile and tell me the print time" or "check on the print and show me the camera" — and it can.

Tools

Related MCP server: Klipper MCP Server

Printer support

Slicing works for every printer OrcaSlicer supports. Printer control speaks these protocols:

You probably don't need to configure anything. If you already set up network printing in OrcaSlicer, the server reads the printer's address and protocol from your machine preset (print_host / host_type). Otherwise ask your assistant to run printer_setup — it scans, reports what it finds, and tells the assistant to ask you which printer you own rather than guessing.

Honest scope: only the Elegoo path has been exercised on real hardware by this project. The rest were built against each protocol's official docs and source (and fact-checked against them), with mock-transport tests asserting the parts that can bite — including that upload never starts a print (asserted for Moonraker, OctoPrint and PrusaLink, whose APIs have an auto-start flag to suppress; Duet, Elegoo and Bambu have no such flag — starting is a separate call by construction). Reports from real machines are welcome.

Adding a protocol is one small class in backends.py.

Setup

Requirements: Python 3.10+, OrcaSlicer (tested with 2.4.1), and — for printer control — a supported printer on your LAN.

git clone https://github.com/ShreddyKrueger75/orcaslicer-mcp
cd orcaslicer-mcp
uv venv --python 3.11 && uv pip install -e .
claude mcp add orcaslicer -- "$(pwd)/.venv/bin/python" "$(pwd)/server.py"

Configuration is optional — sensible defaults are detected per platform:

Safety model

This server can heat hardware and start multi-day prints, so the dangerous paths are guarded:

• Plate type is always pinned. The Orca CLI silently defaults to Cool Plate (45 °C bed) — enough to detach a big part and wreck a hotend (ask us how we know). Every slice sets curr_bed_type explicitly, from the caller, the open GUI project, or DEFAULT_BED_TYPE.

• Stats report what the machine will do, not what the slicer intended: bed/nozzle temps are parsed from the M190/M109 commands in the G-code.

• start_print verifies. Some firmwares silently drop start commands sent while busy; the tool refuses to fire unless the printer is idle, then polls until the job demonstrably starts (or reports the error code if it doesn't).

• Upload never prints. Every backend suppresses its protocol's start-on-upload flag, with tests per protocol that has one.

• Filenames are data, never syntax. A name reaches firmware inside a G-code argument (Duet: M32 "name") and inside URLs; ; or " would let a crafted name append arbitrary G-code (M109 S300) or escape the upload directory. Names are validated before they leave the server.

• No guessing which printer. If several printers are configured and nothing says which you mean, the server asks instead of picking; an unknown host= is refused rather than driven with another printer's protocol and credentials.

• Bed type is whitelisted against OrcaSlicer's own BedType enum (all 7 plates, Supertack included). An unrecognized name would silently become Cool Plate; slice_model rejects invalid values instead.

• Plate-clear gate. Starting a new job while the previous one is COMPLETED/STOPPED (old part likely still on the plate) requires an explicit plate_cleared=True after the user confirms — otherwise the toolhead can crash into the finished part. Concurrent start_print calls are locked out.

• resume only resumes paused prints — never a stopped/errored job where the nozzle may be sitting in a failure.

• Preset edits can't become code. update_profile refuses the post_process key (it executes shell commands at slice time).

• Your GUI choices win. If a project is open in OrcaSlicer, unset slicing parameters come from it rather than from the model's guesses.

• start_print's description instructs clients to confirm with the user — it heats hardware.

Scope note: this is a local, single-user tool. File-path parameters (model_path, output_dir, gcode_path) operate on your filesystem with your permissions, like any local CLI.

How headless slicing works (the non-obvious part)

OrcaSlicer user presets are inheritance deltas (inherits: "<parent>", no type field) and the CLI rejects them as-is. The server resolves the full inheritance chain into flat JSON configs, tags them with type, and satisfies the CLI's compatibility check — which compares the process/filament compatible_printers list against the machine preset's inherits value — by pinning both to the machine's nearest system ancestor. Verified against the OrcaSlicer 2.4.1 source (src/OrcaSlicer.cpp, ~line 2560).

Known limits

• Centauri Carbon CC1 firmware cannot list/delete files or report disk space over SDCP (CC2 can). Uploads to a full or busy printer fail with HTTP 500 — manage storage on the touchscreen.

• OctoPrint and PrusaLink don't report layer counts over their APIs; Duet has no standard camera endpoint. Tools say so instead of failing obscurely.

• The plate-clear gate relies on the printer reporting a finished job. Duet (job.lastFileName) and OctoPrint (100% progress) are inferred; a cancelled OctoPrint job is indistinguishable from idle over its API, so that one case won't trip the gate.

• On Windows the saved config can't be locked to your user with chmod; it inherits the folder's ACL. Prefer PRINTER_* env vars if that matters.

• Cloud host types (PrusaConnect, CrealityPrint, Obico, SimplyPrint, 3DPrinterOS) aren't supported — point the server at the printer's own IP.

• Editing profiles while the OrcaSlicer GUI is open may be overwritten when the GUI exits.

• Slicing timeout is 600 s per call; the CLI reports no progress.

Credits

Elegoo control is pycentauri (Apache-2.0); optional Bambu control is bambulabs-api (MIT); other protocols are spoken directly over HTTP with httpx (BSD-3-Clause). Slicing is OrcaSlicer's own CLI. This project is MIT licensed.