Eight disciplines (8D) problem solving
Eight disciplines (8D) problem solving walks a team through a fixed sequence for resolving a quality escape: form the team, describe the problem, contain it, identify root cause, select and implement corrective actions, verify they work, prevent recurrence, and close out. Most manufacturers require suppliers to answer a formal complaint with an 8D report on a defined clock, typically containment within 24 to 48 hours.
Examples
Containment clock: A customer rejects 400 of 5,000 brackets for a missing weld. Within 24 hours the supplier issues D3: certified stock from a third-party sorter (3 days, $2,800) and a hold on in-transit shipments. Root cause lands on day 10, a bypassed fixture sensor, and verification runs 20 production days before closure.
Occurrence and escape: An 8D on an out-of-spec bore finds the occurrence cause (a worn locating pin) and, separately, the escape cause: final inspection sampled 1 in 50 parts while the defect was running about 1 in 30. The fix pairs a pin replacement schedule with a go/no-go gauge at the operation itself.
Definition
Ford formalized 8D in the 1980s and it spread across automotive into most of discrete manufacturing. Its structural insight is separating containment (D3) from correction (D5 and D6): the customer's line gets protected within a day or two through sorting, certified stock, and holds on in-transit material, while root cause work takes the weeks it actually takes. A D0 planning step is now common, and the 8D is usually the required response format when a customer issues a corrective action request.
The quality of D4 decides everything downstream. Strong 8Ds chase two root causes, not one: why the defect occurred, and why it escaped detection. Weak ones stop at "operator error" and prescribe retraining, which guarantees recurrence. Root cause analysis tools (5 Whys, fishbone diagrams, is/is-not comparison) belong here, and the corrective action should change the process or the design, not the poster on the wall.
Buyers should track 8D cycle time and recurrence, not just submission. A supplier that closes 8Ds in 15 days with no repeats is demonstrating a working quality system; one with three 8Ds on the same failure mode is a candidate for supplier development or resourcing.
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