Fishbone Diagram (Ishikawa) — Root Cause Analysis Tu...

What Is a Fishbone Diagram? A fishbone diagram (Ishikawa diagram or cause-and-effect diagram) is a visual root cause analysis tool that maps potential causes of a problem into categories. Named after its shape — the "head" represents the problem, and the "bones" branch out into cause categories. It was developed by Kaoru Ishikawa in the 1960s at Kawasaki shipyards and became a foundational tool of the Toyota Production System. How Fishbone Fits Into 8D (D4) In 8D D4 (Root Cause Analysis), the fishbone diagram is typically used FIRST — before 5-Why analysis. The team brainstorms ALL possible causes across categories, then uses 5-Why to drill into the most likely ones. The 6M Categories The classic 6M framework for manufacturing: Man (People) — Training, fatigue, communication, experience Machine (Equipment) — Wear, calibration, maintenance, tooling Method (Process) — SOP clarity, work instructions, sequence Material (Raw Materials) — Supplier variation, storage, handling Measurement (Inspection) — Gauge accuracy, measurement method, sampling Mother Nature (Environment) — Temperature, humidity, dust, vibration Some industries add: Management (policies, resources) and Maintenance (preventive schedules). How to Create a Fishbone Diagram Step 1: Write the problem statement at the "head" (right side). Step 2: Draw a horizontal spine line from...