<assembly.subassembly />

assembly.subassembly groups mechanical parts such as housings, brackets, and screws. Import assembly from @tscircuit/core and place the subassembly inside an assembly.device, alongside the board.

import { assembly } from "@tscircuit/core"

export default () => (
  <assembly.device name="product">
    <board width="40mm" height="30mm" thickness="1.6mm" />
    <assembly.subassembly
      name="bracket"
      cadModel={{
        glbUrl: "/bracket.glb",
        positionOffset: { x: 10, y: 0, z: 0.8 },
        rotationOffset: { x: 0, y: 0, z: 90 },
        modelUnitToMmScale: 1,
      }}
    />
  </assembly.device>
)

Supply your own /bracket.glb asset. This example places its reference point on the top surface of a 1.6 mm board centered at the origin.

Property	Description
`name`	Required, non-empty name.
`displayName`	Optional display label.
`cadModel`	Modelprinter string, model URL object, JSCAD model, JSX CAD subtree, or `null`.
`children`	CAD models and nested subassemblies. Can coexist with `cadModel`.

URL objects support glbUrl, gltfUrl, stlUrl, objUrl (with optional mtlUrl), stepUrl, and wrlUrl. Relative URLs use the platform's projectBaseUrl; the viewer must be able to fetch the assets. See cadmodel for model options.

Coordinates and nesting

A top-level subassembly starts at the world origin. Coordinates are in millimetres: +X right, +Y toward the top of the board, and +Z above the board. The board's mid-plane is Z = 0, so its top surface is at half its thickness.

Nested subassemblies inherit the enclosing assembly frame. A cadModel.positionOffset moves only that model; it does not move children or establish a new origin for nested containers. Set offsets on each model that needs them.

You can also use CAD children:

<assembly.subassembly name="hardware">
  <cadmodel modelUrl="/screw.glb" pcbX={10} pcbY={5} pcbZ={0.8} />
  <assembly.subassembly name="cover" cadModel={{ glbUrl: "/cover.glb" }} />
</assembly.subassembly>

Child pcbX, pcbY, and pcbZ specify local model offsets. If you provide positionOffset, it takes precedence over these coordinates. rotationOffset uses degrees; modelUnitToMmScale converts the model's units to millimetres, and modelOriginPosition selects its reference point.

Subassemblies do not accept connectsTo. Use nesting for grouping and explicit model offsets for placement. These elements add CAD geometry without creating PCB components, pads, holes, or schematic symbols. An omitted or null model adds no geometry of its own.

For a complete example, see Mounting 3D models to a board.

Coordinates and nesting​

Coordinates and nesting