ParCAD

Ask Claude for a part. ParCAD makes sure it fits before you print.
Free, open source CAD that AI models drive. Claude writes the part as code, an exact kernel builds it, and every build is measured: the sizes you asked for, the walls, a hinge swung through its whole range. Then export 3MF for your slicer, or STEP.

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Claude adds a snap latch to an SD card box with a lid that prints in place. ParCAD builds it on an exact kernel, swings the lid shut and checks the latch actually catches. Full video.

Status: 0.0.27, experimental. Made by Maging Studio, and the DSL still moves. Every operation is checked against measured geometry (eval/cases/), but none of it has had the years of abuse that make a CAD kernel trustworthy. Measure a part before you machine it.

Start here: Getting started, five minutes in a browser tab. Or give your AI one URL, https://mcp.parcad.dev/mcp, and sign in with GitHub or Google: details.

const plate = box(80, 60, 8).tag("plate");
const wall = box(8, 60, 40).at(-36, 0, 20).tag("wall");

const body = union(plate, wall, { blend: 6 });          // the blend is the fillet
const drilled = body.cut(...grid(2, 2, 36, 40).map(([x, y]) => cylinder(3, 32).at(x, y)));

return drilled
  .edges({ curve: "circle", role: "hole", adjacentTo: { faceNormal: "+z" } })
  .expect({ count: 4 })                                  // a build error, not a surprise
  .fillet(0.8);

You never name an edge by index. You describe it — the circular rims that open onto the top face — and the description still works after you move a hole.

One graph, one exact kernel

Your script builds a small JSON graph, and an exact kernel reads it — OpenCASCADE: real faces and edges, STEP export, and a refusal rather than an approximation when it cannot do something faithfully. The graph is what keeps today's script working after tomorrow's kernel swap.

Every kernel returns valid-looking wrong answers somewhere, OpenCASCADE and NVIDIA's newly open SMLIB included. ParCAD carries eight patches to OpenCASCADE 8.0.1 for the cases its parts ran into, and checks each build itself after the kernel reports success.

![The same manifold block cut open on a plane, cut faces in orange](docs/images/manifold-

... View full README on GitHub