assembly

Mechanical Assembly

Purpose

Build a multi-part assembly from component definitions, create instances, ground a reference frame, apply constraints incrementally, inspect degrees of freedom (DOF) after meaningful steps, detect over-constraint and interference, then export.

Use when

• Two or more parts must be positioned with mechanical constraints.
• You need honest remaining-DOF feedback after each major mate.

Do not use when

• Still designing a single solid (use basic-part or enclosure).
• Need kinematics, gear joints, or path mates (not in the current bounded rigid subset).

Preconditions

• REQUIRED: Parts exist as bodies or will be modelled first.
• RECOMMENDED: inspect_backend_capabilities for assembly support.

Planning rules

1. Model or import each part independently.
2. Create assembly → define components → create instances.
3. Ground exactly one reference instance with fix_instance.
4. Add constraints one at a time; after each major step call inspect_assembly.
5. Prefer under-constraint you can tighten over over-constraint you must undo.
6. Use solver errors as evidence.

Recommended operation sequence

1. REQUIRED — Model parts or import; validate.
2. REQUIRED — create_assembly → define_component → create_instance.
3. REQUIRED — fix_instance on reference (grounds 6 DOF).
4. REQUIRED — Incremental: mate_faces, align_axes (concentric), set_distance, set_angle, …
5. REQUIRED — After each major constraint: inspect_assembly (read remaining_dof).
6. RECOMMENDED — check_interference.
7. REQUIRED — rebuild_assembly → export_assembly.

Geometry / mechanical rules

DOF expectations (diagnostic — always trust inspect_assembly)

State	Typical remaining DOF
Free instance	6
After planar mate_faces	3
After concentric	2
Concentric + axial stop	1
Fully constrained	0

Constraints evaluate in insertion order; second referenced instance moves; grounded never move. Do not stack redundant constraints blindly. Do not reproduce the solver inside the skill; inspect the real output.