8D report CQ-4471, part 774-2210-B8D report CQ-4471, part 774-2210-B
8D report CQ-4471
| FieldField | ValueValue |
|---|---|
| Customer reference | CQ-4471 |
| Part | 774-2210-B, bracket, zinc plated |
| Batch | L-26-0714 |
| Complaint received | 2026-07-29 |
| Report issued | 2026-08-08 |
| Status | D6 verified, D7 in progress |
Burr on the 8 mm bore of part 774-2210-B, batch L-26-0714. Detected by the customer on assembly line 3 on 2026-07-29, by hand during fitting. Two operators were cut and the line stopped 40 minutes. Customer sorting found 61 non-conforming parts out of 300 checked, a rate of 20 percent, on a delivery of 4 800 parts shipped 2026-07-16. The burr sits on the intersection of the 8 mm bore and the top face, height measured at 0.15 to 0.30 mm on our retained samples. The drawing requires all edges free of burr.
Occurrence. The deburring brush on machine CN-06 was worn to 14 mm against 22 mm new, a 36 percent filament loss, while still inside its seven day scheduled interval. Trials on retained parts with a new brush produced no burr. Confirmed. The interval is time based with no wear measurement at change, and it was set when CN-06 ran a softer part at half the current volume. Part 774-2210-B moved to CN-06 in March 2026 and the interval was never revisited.
Ruled out, with evidence: bore diameter drift (log ML-26-0714, 8.02 to 8.05 mm on 8.00 to 8.10, centred), drill wear (tool log CN06-T14, 1 100 parts on a 4 000 part life, within wear limit).
Open: raw material hardness above nominal. Retained coupon not located, so not tested. Hardness check scheduled 2026-08-14 on the next coil from the same supplier lot. This branch stays open. It does not affect D5, which addresses the confirmed causes.
Escape. Control plan CP-774-2210 rev C carries no burr characteristic on the 8 mm bore. No inspection could have caught the condition. Confirmed by document review. Contributing: sampling of 5 parts per box gives roughly a 33 percent chance per box of catching a 20 percent condition. Inspector conformity to the plan was checked and is not a cause (record IR-26-0714).
| CauseCause | ActionAction | Why this oneWhy this one |
|---|---|---|
| Brush wear inside a time based interval | Move the CN-06 deburring brush to a count based interval of 800 parts, with filament length measured and recorded at every change, reject below 18 mm | Count tracks the wear driver. Time does not, and the volume on this machine has doubled since the interval was set |
| Control plan has no burr criterion | Add a burr characteristic on the 8 mm bore to CP-774-2210, tactile check plus 0.05 mm maximum height, and raise sampling to 20 parts per box | The escape cannot be closed by fixing the machine. Nothing was looking for this condition |
Alternative considered and rejected: a 100 percent automated burr inspection. Cycle time and cost are out of proportion to a defect that the interval change removes at source.
| ActionAction | EffectiveEffective | EvidenceEvidence |
|---|---|---|
| Count based brush interval, 800 parts, wear recorded, 18 mm reject limit | 2026-08-03 | Maintenance plan MP-CN06 rev D. Four changes recorded since, filament at 19 to 20 mm at change, none below limit |
| Control plan burr characteristic and sampling at 20 per box | 2026-08-04 | Control plan CP-774-2210 rev D. Three batches run since, 5 400 parts, 240 parts inspected, zero burr found |
| Operator instruction on burr check at final inspection | 2026-08-04 | Work instruction WI-INSP-77 rev B, four inspectors signed off |
Defect rate on the 8 mm bore since implementation: 0 out of 240 inspected across three batches, against 20 percent on the claimed batch.
Disciplines D1 to D6 closed. D7 due 2026-08-21, this report is reissued at D7 closure. Closed by [personne], quality manager. Team recognised at the 2026-08-08 production meeting; S. Nowak located the wear pattern that made the occurrence branch testable.