# SYN-NCR-026 / 8D record / Rev A **SYNTHETIC DEMONSTRATION — fictional engineering records. No employer, customer, real equipment acceptance or supplier engagement is implied.** Part: HX-12 sensor harness Supplier: SYN-014 · Fictional connector supplier Problem: Intermittent sensor disconnects during vibration screening Severity: Major · unreliable process measurement Scope: 750 potentially affected units across two supplier lots ## Traceability register | Lot | Received | Screened | Failures | Status | | --- | --- | --- | --- | --- | | SYN-B1 | 400 | 40 | 9 | Affected / suspect | | SYN-B2 | 350 | 40 | 2 | Affected / suspect | | SYN-A1 | 200 | 40 | 0 | Reference lot / outside suspect window | ## Workflow and required decisions ### Detection / D1–D2 / Define the incident Confirm the failure pattern and define the problem without jumping to a cause. - Review the vibration-screen log and confirm the incident scope — NCR-E01 ### Containment / D3 / Protect production Prevent further use and shipment of suspect lots while the investigation runs. - Place SYN-B1 (400 suspect units) on hold — NCR-E02 - Place SYN-B2 (350 suspect units) on hold — NCR-E02 - Trace and segregate affected WIP / finished assemblies — NCR-E02 - Record supplier containment acknowledgment (simulated) — NCR-E02 ### Investigation / D4 / Test competing explanations Compare component, fixture and setup evidence. Select the hypothesis best supported by the tests. - Review section and pull-test evidence — NCR-E03 - Review the fixture crossover experiment — NCR-E04 ### Root cause / D4 / Occurrence + escape + system Trace the physical failure to its setup and control-system causes. A plausible 5 Why is only useful when each link has evidence. - Review all five causal links and the supplier setup record — NCR-E05 ### Corrective action / D5 / Remove the mechanism Correct suspect hardware and close the process controls that allowed occurrence and escape. - Replace suspect harnesses; retain rework traceability — NCR-E03 - Add die-stop locking and first-piece checks to setup — NCR-E05 - Revise PFMEA, control plan and periodic pull testing — NCR-E05 - Require quality review after process/setup changes — NCR-E05 ### Verification / D6–D7 / Check effectiveness Confirm the corrected process and the new controls. Sampled success supports release but does not eliminate residual risk. - Review all three corrected lots: 0/120 disconnects — NCR-E06 - Verify revised setup and inspection records — NCR-E06 - Assign ongoing supplier effectiveness monitoring — NCR-E06 ### Closure / D8 / Close on evidence Close only after containment disposition, cause, correction and verification are complete. - Approve disposition of the suspect population (simulation) — NCR-E02 - Record demo quality-lead sign-off (simulated) — NCR-E06 ## Five Why / evidence-linked cause chain 1. Why did the sensor disconnect? Terminal contact opened intermittently under vibration. 2. Why could the contact open? The terminal was insufficiently compressed; retention/pull strength was below requirement. 3. Why was the crimp under-compressed? The press shut height increased after the die stop loosened. 4. Why did setup allow that condition? The post-maintenance checklist omitted positive-lock verification and first-piece pull testing. 5. Why did the controls remain incomplete? The setup change did not trigger a PFMEA and control-plan review. ## Evidence register ### NCR-E01 / Vibration-screen incident log SYN-B1: 9/40 failures. SYN-B2: 2/40. Reference SYN-A1: 0/40. Disconnection occurs under vibration and disappears at rest. Detection; sampled incidence is not an estimate of every unit in a lot. ### NCR-E02 / Traceability & containment register 400 units in SYN-B1 and 350 in SYN-B2 share the same supplier press setup window. Trace links incoming stock, WIP and finished assemblies to those lots. Hold population is 750 suspect units; do not treat all 750 as confirmed failures. ### NCR-E03 / Terminal section & pull test Suspect crimp height: 2.12–2.18 mm against a 1.95–2.00 mm requirement. Pull strength: 18–28 N against a ≥40 N requirement. Reference terminals meet both requirements. Physical evidence supports insufficient terminal compression. ### NCR-E04 / Harness / fixture crossover test Failure follows the suspect harness across two independently checked fixtures. Reference harnesses remain stable on both fixtures. Weakens the test-fixture explanation; isolates the component. ### NCR-E05 / Supplier setup review Die stop was not positively locked after maintenance. The setup checklist omitted lock verification, and the process change did not trigger a PFMEA/control-plan review. Occurrence, escape and systemic control gaps must all be addressed. ### NCR-E06 / Corrective-action verification Three corrected lots: 40 assemblies each, zero disconnects across 120 screened assemblies. Crimp height 1.96–1.99 mm; pull checks 48–61 N. Revised setup and inspection records are present. Limited sampled verification. Zero observed failures does not prove zero residual risk. ## Responsibilities and closure Fictional roles: quality lead owns incident/containment; supplier engineering owns setup correction; receiving quality owns lot holds; supplier quality owns sampled verification and ongoing monitoring. No real messages are sent. Sign-offs exist only in the visitor's temporary browser session. A 0/120 result is limited evidence, not proof of zero risk.