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Tutorial: Parse a STEP file

In this tutorial you will parse a CAD file with cadling, inspect the resulting document, chunk it for RAG, and export it. Allow ~10 minutes.

Prerequisites

Section titled “Prerequisites”
  • cadling installed (pip install -e ".[all]" inside the conda env — see Installation).
  • A CAD file. Any .step, .stl, .brep, or .iges file works. The repo ships an example part.step at its root.

1. Convert the file

Section titled “1. Convert the file”
from cadling import DocumentConverter, ConversionStatus


converter = DocumentConverter()
result = converter.convert("part.step")


assert result.status in (ConversionStatus.SUCCESS, ConversionStatus.PARTIAL)
doc = result.document
print(f"Parsed {len(doc.items)} items from a {result.status.name} conversion")

DocumentConverter detects the format, selects a backend, and runs the Build → Assemble → Enrich pipeline, returning a CADlingDocument.

2. Inspect the document

Section titled “2. Inspect the document”
for item in doc.items[:10]:
    print(type(item).__name__, getattr(item, "entity_type", ""))


# Topology: the entity-reference graph
topo = doc.topology
if topo is not None:
    print("topology nodes:", len(topo.adjacency_list))

Items are typed: STEPEntityItem, MeshItem, AssemblyItem, AnnotationItem.

3. Chunk it for RAG

Section titled “3. Chunk it for RAG”
from cadling.chunker.hybrid_chunker import CADHybridChunker


chunker = CADHybridChunker(max_tokens=512, overlap_tokens=50)
chunks = list(chunker.chunk(doc))
print(f"{len(chunks)} chunks")
print(chunks[0].text[:200])

Each chunk carries meta with entity types, a topology subgraph, embeddings, and a 3D bounding box — ready to index in a vector database.

4. Export

Section titled “4. Export”
import json
from pathlib import Path


# export_to_json() returns a dict; export_to_markdown() returns a string.
Path("part.json").write_text(json.dumps(doc.export_to_json(), indent=2))
Path("part.md").write_text(doc.export_to_markdown())

Or do it all from the CLI

Section titled “Or do it all from the CLI”
Terminal window
cadling convert part.step --format json --pretty -o part.json
cadling chunk part.step --max-tokens 512 --overlap 50 -o chunks.jsonl
cadling info part.step

Where to next

Section titled “Where to next”