Manufacturing Process
Assembly & Subassembly
装配与子装配
Joining stamped and machined parts through riveting, pressing, welding or fastening into assemblies.
Process Steps
- Components kitted
- Alignment fixture
- Joining operation
- Functional check
What assembly and subassembly mean here
Direct answer: a subassembly is two or more components joined into one part before it reaches the customer's line — a stamped housing with a bushing pressed in, a bracket with a weld nut, a cover staked onto a body, a solenoid frame with a riveted pole.
It is usually bought because the supplier already makes the components, the tooling and the gauges, and the customer would rather receive one part number than five.
The joining methods used on stamped components
| Method | How it works | Typical use |
|---|---|---|
| Projection / spot welding | Local resistance weld at a formed projection or a spot | Brackets, plates, tapped bosses |
| Riveting / staking | A rivet or a formed post is upset to lock parts together | Pole pieces, covers, laminations |
| Clinching | Material is pressed into an interlock without heat or added parts | Sheet-to-sheet joining, especially coated stock |
| Press-fit | An interference fit between a bushing, pin or bearing and a bore | Bushings, bearing seats, sleeves |
| Adhesive | A structural or gasketing bond | Sealing, dissimilar materials, vibration damping |
| Screws and fasteners | Machine screws, weld nuts, clinch studs | Serviceable joints and high-load connections |
Tolerance stack-up is the real work
Every individual part can be inside its own tolerance and the assembly still not fit. That is why the datum scheme matters more than the individual tolerances: a subassembly should be dimensioned from a common datum that exists in the fixture, not from the sum of features that were each measured on their own. Where a fit is critical, the practical answer is often to control the assembly dimension directly and loosen one of the contributing parts.
Why buy it as a subassembly?
- One part number, one incoming inspection, one supplier to qualify.
- Components and tooling already exist, so the joining operation is cheap to add.
- Function is tested before shipment — a magnetic circuit, a seal or a fit is verified as an assembly instead of discovered on the line.
- Freight and handling drop when five boxes become one.
Frequently asked
Can you supply a subassembly rather than loose parts?
Yes. Where the components are stamped, drawn or machined in-house, the joining operation is added to the route and the assembly is inspected and packed as one part number.
Which joining method should I specify?
Whatever the function and the material allow: welding for structural steel joints, staking or riveting for pole pieces and laminations, clinching for coated sheet, press-fit for bushings and bearings. The method should be chosen with the assembly loads in mind, not only with manufacturability.
How is the assembly inspected?
Against the assembly drawing with the datum scheme stated, plus a functional check where the assembly has a function: push-out force on a press-fit, weld peel or torque on a welded joint, magnetic performance on a magnetic circuit.
Do subassemblies change the PPAP scope?
They add to it. A subassembly needs its own process flow, PFMEA and control plan, and the customer usually wants the assembly dimension and the joining parameters controlled as key characteristics. See PPAP capability.
Related: CNC milling · hole flanging · tapping · PPAP capability · deep drawing