Assembly structure — grouping components inside a larger machine What is the correct term for a collection of related parts combined into a smaller unit that itself fits into a larger overall assembly?

Introduction / Context:
Complex machines are organized hierarchically to simplify design, documentation, manufacturing, and maintenance. Understanding this hierarchy helps in reading bills of materials (BOMs), planning builds, and managing configuration.

Given Data / Assumptions:

• A large product is composed of many parts and intermediate groupings.
• Documentation includes part numbers, assemblies, and exploded views.
• Standard BOM structure is used (part → subassembly → major assembly → final product).

Concept / Approach:
A “subassembly” is a self-contained grouping of components performing a specific function within a larger assembly. Subassemblies can be built and tested separately, then integrated, improving throughput and quality.

Step-by-Step Solution:
Identify functional groupings (e.g., gearbox, valve block).Assign subassembly part numbers and create their own working drawings.Define interfaces (mounting, electrical connectors) to the next higher assembly.Integrate subassemblies into the major assembly per the master BOM.

Verification / Alternative check:
Exploded assembly drawings show subassemblies as logical units with item balloons grouped together. Procurement and production schedules often track at the subassembly level.

Why Other Options Are Wrong:

• External assemblies: nonstandard term; ambiguous.
• Component assemblies: redundant phrasing not typically used formally.
• Major assemblies: the next level up, containing multiple subassemblies.

Common Pitfalls:
Poorly defined interfaces or mixing vendor-supplied modules with in-house parts without clear boundaries complicates builds.

Final Answer:
Subassemblies