| # | 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 | Assembly operators at AutoTech Corp. Line 3 reported issue. Affects end-customer vehicle harness assembly. |
| Problem (What) | Connector housing (CH-4521) cracking at snap-fit latch area during assembly press-in operation |
| 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) | Parts crack under normal insertion force (50-60N) which is within specification. Root cause under investigation. |
| 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) | 12 of 200 units inspected at customer site (6% defect rate). Internal re-inspection of quarantined stock found 45 of 1,988 units with micro-cracks (2.3%). |
| Frequency (How Often) | First occurrence with this part number. No similar defects in previous 18 months of production. |
| 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 thin-wall section creates stress concentration point |
| where | Cracks found on parts produced by Mold #1 on Press #7 | No cracks on parts from Mold #2 or other presses | Mold #1 has partially blocked cooling channel at Position B; Press #7 has pressure sensor drift | Cooling blockage + pressure variation specific to Mold #1/Press #7 combination |
| when | Batch B2026-0187 produced on 2026-02-25 (night shift) | No defects in previous 18 months of production or day shift batches | Cooling channel blockage accumulated gradually; pressure sensor drift occurred after last calibration (2026-01-15) | Gradual degradation reached critical threshold during this production run |
| 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 nature suggests process variation rather than systematic design flaw |
| # | 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 1: | Why did the connector housing crack at Position B? | Ans: | Residual stress at weld line exceeded material strength due to uneven cooling |
| Why 2: | Why was cooling uneven at Position B? | Ans: | Cooling channel in Mold #1 was partially blocked, causing hot spot at thin-wall section |
| Why 3: | Why was the cooling channel blocked? | Ans: | Mineral deposits accumulated over 8 months without preventive maintenance cleaning |
| Why 4: | Why was there no preventive maintenance for cooling channels? | Ans: | TPM checklist did not include cooling channel flow rate monitoring or periodic flushing |
| Why 5: | Why was cooling channel maintenance not in the TPM checklist? | Ans: | Original FMEA did not identify cooling degradation as a potential failure mode for this mold design |
| Why 1: | Why did injection pressure fluctuate on Press #7? | Ans: | Pressure sensor RC-2 had calibration drift beyond ±3% tolerance |
| Why 2: | Why did the pressure sensor drift? | Ans: | Sensor exceeded recommended calibration interval (6 months since last calibration vs. 3-month recommended cycle) |
| Why 3: | Why was the calibration interval exceeded? | Ans: | No automated calibration tracking system — relies on manual scheduling which was missed |
| 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 |
| # | Corrective Action | Owner | Completion Date | Status |
|---|---|---|---|---|
| 1 | Clean and flush all cooling channels in Mold #1; implement quarterly preventive maintenance schedule for cooling system | Chen Hao | 2026-03-05 | Completed |
| 2 | Recalibrate pressure sensors on Press #7 and add real-time pressure monitoring alarm (SPC) | Zhang Min | 2026-03-07 | Completed |
| 3 | 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 |
| Name | Contribution | Recognition Type |
|---|---|---|
| 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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