CAD to Print MCP

A local MCP server that lets Codex and other MCP clients move a design through FreeCAD → STL → OrcaSlicer configuration → G-code → Moonraker printer. It uses stock OrcaSlicer's command-line interface and keeps every exported STL, derived preset, slice manifest, and G-code in a separate output location.

What it does

• Inspect a FreeCAD .FCStd document and export a named solid to STL.

• Find, inspect, and derive OrcaSlicer machine, process, and filament presets. Derived presets are copies; originals stay untouched.

• Preview and run a slice with specified presets and settings. Each run records input hashes, command arguments, effective settings, logs, and output artifacts.

• Read G-code metadata, query a Moonraker printer, upload G-code, and start an uploaded print as a distinct step.

It does not edit the open OrcaSlicer GUI, paint supports, create CAD geometry from a text description, or control printers other than Moonraker yet. Agents can use their own CAD tools to create .FCStd files before using this server. OrcaSlicer itself is not bundled.

Related MCP server: FreeCAD Robust MCP Server

Requirements

• Python 3.10 or newer

• FreeCAD with FreeCADCmd for .FCStd inspection/export

• OrcaSlicer with command-line mode

• Optional: a printer running Moonraker for status, upload, and print start

The server runs locally over MCP stdio. It does not open a listening port.

Install

git clone https://github.com/Kayrim/cad-to-print-mcp.git
cd cad-to-print-mcp
py -3 -m venv .venv
.\.venv\Scripts\python.exe -m pip install -e .

On macOS/Linux, use python3 -m venv .venv and .venv/bin/python -m pip install -e ..

Set these environment variables in your MCP client or shell:

Connect Codex

Use the Python executable from your new virtual environment. On Windows:

codex mcp add cad-to-print -- "C:\absolute\path\to\cad-to-print-mcp\.venv\Scripts\python.exe" -m cad_to_print_mcp.server
codex mcp list

For other MCP clients, configure a local stdio server with the same executable and -m cad_to_print_mcp.server arguments. Restart the client after adding it.

Example agent workflow

1. check_setup and inspect_freecad_document to choose the printable solid.

2. export_freecad_stl to create a mesh from the chosen FreeCAD object.

3. find_profiles for compatible machine, process, and filament presets. read_profile and derive_profile can make a variant with support, infill, speed, or other settings.

4. preview_slice, then run_slice. Or call prepare_print_job to export the selected FreeCAD object and slice it in one step. Review the manifest, logs, and generated G-code. The preset files should match the actual printer, nozzle, material, and firmware.

5. get_printer_status, then upload_print_file. Uploading alone never starts a print.

6. When ready, call start_uploaded_print using the returned upload ID. It refuses to start while the printer reports an active or paused job.

The run_slice tool accepts a .3mf with embedded settings or an STL/OBJ/STEP with all three preset JSON files. Common overrides such as layer_height, enable_support, support_type, sparse_infill_density, and wall_loops are directly validated. For other settings, derive a copy of a bundled preset and pass that copy to run_slice. OrcaSlicer validates the resulting configuration during slicing.

Safety and privacy

• The server never runs shell commands assembled from tool inputs. It invokes FreeCAD and OrcaSlicer with argument arrays.

• It never edits original CAD files or OrcaSlicer presets.

• derive_profile refuses script, G-code, print host, and credential fields. read_profile redacts credentials.

• upload_print_file and start_uploaded_print are separate calls. Print start checks that Klipper is ready and no job is active.

• Generated files and manifests can contain model names and local paths. The outputs/ directory is Git-ignored.

• Review G-code and printer preparation before starting a physical print. The server cannot check bed clearance, filament loading, or hardware condition.

Development

.\.venv\Scripts\python.exe -m unittest discover -s tests -v

Tests use local fixtures and mocked process/printer calls. A live smoke test should be run with your own FreeCAD, OrcaSlicer, presets, and Moonraker setup before printing. See docs/architecture.md for the adapter boundaries and roadmap.

License

MIT. This project is independent of FreeCAD, OrcaSlicer, and Moonraker.