Connector housing CH-4521 fractures at the snap-fit latch area during the assembly press-in operation. Failure occurs under a normal insertion force of 50-60N, within the specified insertion-force range on drawing CH-4521 Rev.D.
| # | Action | Purpose | Scope | Owner | Time | Status |
|---|---|---|---|---|---|---|
| 1 | Quarantine remaining stock of batch B2026-0187 at warehouse | Prevent defective parts from reaching assembly line | All CH-4521 from batch B2026-0187 (1,988 units) | Wang Jun, Warehouse Manager | 2026-02-28 | - |
| 2 | Notify customer quality team and issue containment report | Customer awareness and traceability | AutoTech Corp. SQE department | Li Wei, SQE | 2026-02-28 | - |
| Name | Role | Department | Contact |
|---|---|---|---|
| Li Wei | Team Leader | Quality Assurance | - |
| Zhang Min | Process Engineer | Manufacturing Engineering | - |
| Chen Hao | Mold Technician | Tooling | - |
| Liu Fang | Material Specialist | Material Engineering | - |
| Wang Jun | Production Supervisor | Production | - |
| Item | Content |
|---|---|
| Who | First detected by assembly operators at the customer (AutoTech Corp.) on Line 3 — the defect escaped internal inspection and was found at the customer plant. Affects end-customer vehicle harness assembly. |
| Problem (What) | Connector housing CH-4521 fractures at the snap-fit latch area during the assembly press-in operation. Failure occurs under a normal insertion force of 50-60N, within the specified insertion-force range on drawing CH-4521 Rev.D. |
| Location (Where) | Cracks observed at the thin-wall section near snap-fit feature, right side latch (Position B) |
| Time (When) | First reported on 2026-02-28 during vehicle assembly at customer plant. Parts from batch B2026-0187 produced on 2026-02-25. |
| Reason (Why) | A fractured snap-fit latch loses retention force and can allow connector disengagement during vehicle service, creating a harness reliability and potential safety risk; the defect also escaped to the customer. Because failure occurs within the specified insertion force, the part does not meet its required strength. Root cause is determined in D4 and is not pre-judged here. |
| How | Crack initiates at gate vestige area and propagates along weld line to snap-fit base. Brittle fracture pattern observed under microscope. |
| Quantity (How Many) | Customer site: 12 of 200 units inspected were cracked (6%). Internal 100% re-inspection (20x microscope) of the quarantined remainder of the same batch found 45 of 1,988 units with micro-cracks (2.3%). All defective units belong to batch B2026-0187. |
| Frequency (How Often) | Confined to a single batch (B2026-0187) — the first batch affected for this part number. No similar defects in the previous 18 months of CH-4521 production or in any other batch. |
| Dimension | IS | IS NOT | Distinction | Possible Cause |
|---|---|---|---|---|
| what | Cracking at snap-fit latch area (Position B) on connector housing CH-4521 | No cracking at Position A (left side latch) or other snap-fit features | Position B has thinner wall section (0.8mm vs 1.2mm at Position A) and weld line intersection | Weld line at the thin-wall section is a likely stress-concentration point (hypothesis — to be verified in D4) |
| where | Cracks found on parts produced by Mold #1 on Press #7 | No cracks on parts from Mold #2 or other presses | Parts trace to Mold #1 / Press #7; these differ from Mold #2 and other presses in cooling-channel condition and pressure-sensor calibration status | Suspected cooling and pressure variation specific to the Mold #1 / Press #7 combination (to be verified in D4) |
| when | Batch B2026-0187 produced on 2026-02-25 (night shift) | No defects in previous 18 months of production or day shift batches | This batch ran on the night shift; the Press #7 pressure sensor had not been calibrated since 2026-01-15, and Mold #1 had been in service ~8 months without cooling-channel maintenance | Suspected gradual degradation reaching a critical threshold during this run (to be verified in D4) |
| extent | 6% defect rate at customer site (12/200); 2.3% micro-crack rate in quarantined stock (45/1988) | Not 100% defective — majority of parts pass functional test | Defect rate correlates with position in mold cavity and injection cycle timing | Intermittent rate suggests process variation rather than a systematic design flaw (hypothesis) |
| # | Interim Action | Owner | Deadline | Verification | Status |
|---|---|---|---|---|---|
| 1 | 100% inspection of quarantined batch B2026-0187 using microscope at 20x magnification | QA Team | 2026-03-01 | 45 additional units with micro-cracks identified and scrapped | Completed |
| 2 | Switch to backup mold (Mold #2) for ongoing production | Chen Hao | 2026-03-01 | First article inspection passed on backup mold output | Completed |
| 3 | Ship replacement parts from known-good batch B2026-0165 to customer | Wang Jun | 2026-03-02 | - | Completed |
| Why # | Question | Answer | Evidence / Verification |
|---|---|---|---|
| 1 | Why did the connector housing crack at Position B? | Residual stress at weld line exceeded material strength due to uneven cooling | - |
| 2 | Why was cooling uneven at Position B? | Cooling channel in Mold #1 was partially blocked, causing hot spot at thin-wall section | - |
| 3 | Why was the cooling channel blocked? | Mineral deposits accumulated over 8 months without preventive maintenance cleaning | - |
| 4 | Why was there no preventive maintenance for cooling channels? | TPM checklist did not include cooling channel flow rate monitoring or periodic flushing | - |
| 5 | Why was cooling channel maintenance not in the TPM checklist? | Original FMEA did not identify cooling degradation as a potential failure mode for this mold design | - |
| Why # | Question | Answer | Evidence / Verification |
|---|---|---|---|
| 1 | Why did injection pressure fluctuate on Press #7? | Pressure sensor RC-2 had calibration drift beyond ±3% tolerance | - |
| 2 | Why did the pressure sensor drift? | Sensor exceeded recommended calibration interval (6 months since last calibration vs. 3-month recommended cycle) | - |
| 3 | Why was the calibration interval exceeded? | No automated calibration tracking system — relies on manual scheduling which was missed | - |
Cooling channel partial blockage in Mold #1 caused uneven cooling at Position B, leading to residual stress and reduced weld line strength
Injection pressure fluctuation on Press #7 exceeded tolerance, causing inconsistent packing at thin-wall sections
Control plan did not include wall thickness measurement at Position B (critical thin-wall area near weld line)
| ID | Root Cause Description | Type | Contribution | Verification Method |
|---|---|---|---|---|
| 1 | Cooling channel partial blockage in Mold #1 caused uneven cooling at Position B, leading to residual stress and reduced weld line strength | Occurrence | 60% | Thermal imaging confirmed hot spot; cleaning restored normal temperature profile |
| 2 | Injection pressure fluctuation on Press #7 exceeded tolerance, causing inconsistent packing at thin-wall sections | Occurrence | 30% | Pressure sensor calibration drift confirmed; recalibration resolved variance |
| 3 | Control plan did not include wall thickness measurement at Position B (critical thin-wall area near weld line) | Escape | 10% | Control plan review confirmed missing checkpoint |
| # | Root Cause | Corrective Action | Owner | Completion Date | Status |
|---|---|---|---|---|---|
| 1 | RC1 | Clean and flush all cooling channels in Mold #1; implement quarterly preventive maintenance schedule for cooling system | Chen Hao | 2026-03-05 | Completed |
| 2 | RC2 | Recalibrate pressure sensors on Press #7 and add real-time pressure monitoring alarm (SPC) | Zhang Min | 2026-03-07 | Completed |
| 3 | RC3 | Update control plan to add wall thickness check at Position B (min 0.8mm, target 1.0mm) | Li Wei | 2026-03-06 | Completed |
| # | Validation Item | Method | Result | Time | Status |
|---|---|---|---|---|---|
| 1 | Run 500-piece validation batch on Mold #1 after cooling channel cleaning | Cpk study on wall thickness at Position B, snap-fit insertion force test | Cpk = 1.67 (target > 1.33), 0 cracks in 500 units | 2026-03-08 | Completed |
| 2 | Monitor Press #7 pressure SPC charts over 2 weeks of production | Real-time SPC monitoring with +/- 3% alarm limits | All readings within control limits for 14 consecutive production days | 2026-03-21 | Completed |
| # | Preventive Action | Owner | Completion Date | Doc Update | Status |
|---|---|---|---|---|---|
| 1 | Add cooling channel flow rate monitoring to all injection molds as part of TPM checklist | Chen Hao | 2026-04-01 | TPM-SOP-012 Rev.C | In Progress |
Connector housing cracking caused by cooling channel blockage and pressure fluctuation. Corrective actions implemented and verified. Customer resumed production on 2026-03-10.
Preventive maintenance for mold cooling systems must be included in TPM schedules. Critical thin-wall areas near weld lines should be identified during DFMEA and included in control plans.
2026-03-21
| Person | Contribution | Reward |
|---|---|---|
| Chen Hao | Root cause identification through thermal imaging analysis | Technical Excellence |
| Zhang Min | Rapid implementation of SPC monitoring system | Quick Response |
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