<assembly.part />

assembly.part is a generic mechanical component, such as a bearing, bracket, or cover. Give it a stable name and optionally supply a CAD model. It has no PCB footprint, schematic symbol, or electrical ports.

Mount a bearing model

This example seats an 8 × 22 × 7 mm bearing in a printed housing. mountedTo=".HOUSING > .bearingSeat" selects the pocket floor; mountFace="base" selects the bearing's authored bottom reference. The bearing's origin is at that bottom face, so no CAD offset is needed.

import { assembly } from "tscircuit"
import { BearingHousing, bearingModel } from "./models"

export default () => (
  <assembly.device>
    <assembly.printedpart name="HOUSING" jscad={<BearingHousing />}>
      <assembly.referencesurface name="bearingSeat" centerZOffset={4} />
      <assembly.referencesurface name="boltSeat"
        centerXOffset={22} centerYOffset={12} centerZOffset={6} />
    </assembly.printedpart>
    <assembly.part name="BEARING"
      cadModel={bearingModel}
      mountedTo=".HOUSING > .bearingSeat" mountFace="base">
      <assembly.referencesurface name="base" normalDirection="z-" />
    </assembly.part>
    <assembly.bolt name="BOLT" model="hexsocketbolt_m3_l10mm"
      fastenedTo=".HOUSING > .boltSeat" />
  </assembly.device>
)

The housing, bearing races and recessed shields are modeled in models.tsx; the bolt uses an existing JSCAD Electronics model. assembly.referencesurface adds attachment frames to these parts without adding material. The bolt uses its own fastenedTo prop.

For a purchased bearing CAD file, replace cadModel={bearingModel} with modelUrl="./bearing.glb" and keep the references at the asset's physical mounting locations. This example's authored model has its bottom at local Z = 0.

Part properties

Property	Description
name	Required stable identity. Trimmed and must not be empty.
displayName	Optional human-facing name.
purchaseUrls	Optional purchase links.
supplierPartNumbers	Optional supplier part numbers, e.g. { jlcpcb: ["C123"] }.
model	Modelprinter/footprinter specification or an HTTP(S) model URL.
modelUrl	Imported model URL or asset path.
cadModel	Existing CAD formats and model-alignment transforms, including CAD JSX; see cadmodel.
mountedTo	Target face selector, such as .HOUSING > .bearingSeat, or compact path HOUSING.bearingSeat.
mountFace	This part's named mating face. Supply with mountedTo.
mountOffset	Signed distances along the target face's local X/Y tangents: { x?, y? }. Omitted axes are zero.
mountGap	Nonnegative clearance along the target's outward normal, default zero.

Supply at most one of model, modelUrl, or cadModel. Omit all three for a part with no geometry. cadModel={null} also keeps the identity without rendering a model; it cannot be combined with another model source. For a jscad JSX prop, use assembly.printedpart.

Placement and CAD alignment

Standalone unmounted parts use the world origin. Nested parts inherit the nearest assembly's full placement, including tilt. A face mount sets the complete position and orientation; its children and reference surfaces follow that frame. Use mountOffset for in-plane adjustment and mountGap for separation. Both require mountedTo.

cadModel.positionOffset and rotationOffset align the mesh within that frame. They do not move the assembly origin, its children, or its reference surfaces. An imported model needs authored reference surfaces; core does not infer mounting faces from its mesh.

Coordinates are in millimetres in a right-handed frame: +X right, +Y top, and +Z above. Target selectors resolve within the nearest assembly.device, including targets declared later. A selector must match exactly one face; missing or ambiguous references and mounting cycles report errors.

An assembly.screen can target the part's identity with connectsTo=".BEARING"; this uses its assembly origin and creates no electrical connections. Use assembly.subassembly to move a group through one mounting constraint.