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4.14 Final Inspection and Traceability

Final inspection is the last line of defense before the product leaves the controlled factory environment. While electrical testing validates the logic, it cannot detect mechanical liabilities like a connector that is partially mated but not locked, or a label that is about to fall off. This stage is a mechanical audit ensuring the harness is robust, dimensionally compliant, and properly protected for the logistics chain.

4.4.14.1 Mechanical Audit: The Physical Integrity Check

The electrical tester confirms the electrons flow; the mechanical audit confirms the assembly will survive installation. This process is primarily visual and tactile.

A) Connector Seating (Push-Click-Pull)

The most common field failure in wire harnesses is a connector backing out due to vibration because the primary lock was not fully engaged.

  • The Mandate: Every connector mating (if applicable) and every terminal insertion must undergo the Push-Click-Pull test.
      • Push: Insert the terminal/connector until it seats.
      • Click: Listen/feel for the audible mechanical click of the locking tang.
      • Pull: Apply a light pullback force (not enough to break the wire, but enough to test the lock) to verify retention.

  • Visual Check: For connectors with TPA (Terminal Position Assurance), verify the TPA is flush and locked. If the TPA protrudes, a terminal is not fully seated.

    • B) Dimensional and Label Audit

    • Tolerances: Critical branch lengths and breakout positions must be measured against the drawing tolerances (typically ± 10 mm).
    • Labeling: Verify Label Position (distance from connector) and Legibility. A label that is upside down or barely readable is a process indicator of poor workmanship.
    • Strain Relief: Inspect the cable exit at backshells and tie-wrap points.
      • Defect: If the wire is pulled tight against the connector pin (no service loop), it will fail under vibration.
      • Defect: If the backshell screw is loose or the tie-wrap can slide along the bundle, strain relief is inactive.

    4.4.14.2 Traceability: The Digital Handshake

    Before the unit is packed, its digital history must be closed. This is the final step in the MES (Manufacturing Execution System) workflow.

    • Test Linkage: The inspector scans the harness Serial Number (SN) to verify that the Electrical Test Status is "PASS." The system must block packaging if the unit failed continuity or Hi-Pot and was not re-tested.
    • As-Built Configuration: Verify that any deviations or engineering change orders (ECOs) active for this build batch are physically present (e.g., "Add ferrite core to P2").

    4.4.14.3 Packaging: Logistics Protection

    A harness is a flexible, tangled component. Improper packaging leads to bent pins, crushed insulation, and "spaghetti" tangles that frustrate the customer.

    A) Coiling Limits

    • Minimum Radius: Harnesses must be coiled, not folded. The coil diameter must respect the static bend radius (typically 3x to 5x the bundle diameter) to prevent kinking wires or fracturing foil shields.
    • Securing: Coils should be secured with Velcro ties or twist ties, not tight plastic zip ties that crush the insulation during storage.
    • Cap Protection: All connectors must be capped or bagged to prevent Foreign Object Debris (FOD) ingress and pin damage. Unprotected male pins are easily bent during shipping.

    B) Bag-and-Tag

    • Individual Bagging: High-value or complex harnesses should be individually bagged to prevent tangling with others in the shipping box.
    • Desiccant: For harnesses with nylon connectors (hygroscopic) or silver plating (tarnish risk) shipping via ocean freight, desiccant packs are mandatory to control humidity.
    • Box Mapping: The shipping label on the outer box must verify the Quantity and list the Range of Serial Numbers contained within.

    Final Checklist: Inspection and Packaging

    Mandate

    Criteria

    Verification Action

    Lock Verification

    Terminals and connectors mechanically locked.

    Push-Click-Pull test performed on 100% of connections.

    Locking Aids

    TPA and CPA devices fully seated.

    Visual check: TPA is flush with the housing face; not protruding.

    Electrical Status

    Unit passed Continuity/Hi-Pot.

    MES scan confirms "PASS" status before generating the shipping label.

    Connector Protection

    Pins protected from bending/debris.

    Dust caps or ESD bags installed on all connectors.

    Coil Integrity

    Harness coiled loosely; no sharp kinks or folds.

    Visual check: Coil diameter respects minimum bend radius.

    Box Traceability

    Shipping box linked to contents.

    Box label lists specific Serial Numbers inside, not just part number.

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