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Root Cause Analysis (Fishbone & 5-Why)

Problem Solving

Standalone RCA using Fishbone and 5-Why for recurring quality issues. Elimination of recurrence and standard RCA template.

Executive Summary

Recurring defects suggested that past corrective actions had addressed symptoms, not root causes. This project applied Fishbone (Ishikawa) and 5-Why in a structured way: cross-functional team, fishbone for potential causes (6M), then 5-Why to drill to root cause and verify with data. Outcomes: elimination of recurrence for targeted issues and a standard RCA template for the site.

Elimination of recurrence for targeted defect types
Standard RCA template and training
Stronger corrective actions linked to root cause

Context & Problem

The same types of defects kept coming back. Corrective actions had been one-off fixes without finding the underlying cause. The organization needed a repeatable RCA process (Fishbone + 5-Why) and discipline to verify root cause with data before implementing permanent fixes.

Methodology & Frameworks

Fishbone (6M: Man, Machine, Method, Material, Measurement, Environment) to brainstorm potential causes. 5-Why for each likely cause until a root cause was reached; each \"why\" verified with data. Corrective actions addressed the verified root cause and were validated for effectiveness.

Implementation

RCA was triggered for recurring or high-impact defects. A facilitator led the fishbone and 5-Why sessions; causes were documented and verified. Corrective actions were assigned with due dates and linked to the root cause. A simple template and short training were rolled out.

Outcomes

Recurrence eliminated for the defect types that went through full RCA.
Standard template—RCA format and checklist used across the site.
Stronger CAPAs—corrective actions clearly tied to root cause and verification.

Lessons Learned

Stopping at the first \"why\" often misses the real root cause. Cross-functional input in the fishbone improved completeness. Verifying root cause with data prevented fixing the wrong thing. A standard template made RCA repeatable and auditable.