An AI company building agents for industrial CAD workflows needed a system that edits CAD models using text commands — "change the radius of the upper hole to 3mm" or "add 2 holes to the upper surface." We built a fully on-premise LLM-powered backend that reads .stp files, interprets text commands, and applies programmatic edits.
The client's AI agents need a backend system that receives a .stp (STEP) CAD file and a text editing command, and outputs a modified .stp file with the requested changes applied. The system must run entirely on-premise — no cloud API dependency — because their industrial customers require data sovereignty. The challenge is bridging natural language understanding with precise geometric operations on complex CAD data.
A fully on-premise LLM-powered CAD editing backend with three modules:
1. CAD model parser — loads .stp files and extracts all relevant geometric and topological information into structured JSON, using CadQuery and PythonOCC.
2. LLM module — an on-premise model (Mistral-7B, Phi-2, or Llama variant) interprets the structured CAD data and the user's text command, and outputs structured edit operations.
3. CAD modifier module — translates the LLM output into programmatic editing operations applied directly to the .stp file.
Supported operations include: modifying existing features ("change the radius"), global scaling ("scale the entire part down by 10%"), adding new features ("add 2 holes to the upper surface"), and removing features ("remove the hole from the bottom surface").
- Natural language commands applied to STEP CAD files programmatically
- Fully on-premise — no cloud API, no internet required
- Supports modify, scale, add, and remove operations
- On-premise LLM (Mistral-7B / Phi-2 / Llama variants)
- CAD parsing via CadQuery and PythonOCC
- Optional RAG system for handling large CAD files exceeding context window
The system demonstrates text-to-CAD editing on .stp files with full data sovereignty. It runs on-premise with GPU acceleration. The architecture supports extension to additional CAD operations and model types.