Quality Tools
Fishbone Diagram Generator
Build an Ishikawa cause-and-effect diagram to organise potential causes across the 6M categories and steer root cause analysis.
High Defect Rate in Electronic Assembly
Man (People)
Machine (Equipment)
Material
Method (Process)
Measurement
Mother Nature (Environment)
🔍 Next Steps for Root Cause Analysis
• Prioritize causes: Use data, voting, or impact assessment to identify the most likely causes
• Investigate root causes: Use the “5 Whys” technique to dig deeper into each potential cause
• Collect evidence: Gather data to support or refute each potential cause
• Develop action plans: Create specific actions to address confirmed root causes
• Monitor results: Track improvements after implementing corrective actions
Understanding fishbone diagrams
A fishbone diagram, also known as an Ishikawa diagram or cause-and-effect diagram, is a visual tool used to systematically identify and organize potential causes of a problem. Named after its fish-like appearance, it was developed by Kaoru Ishikawa in the 1960s.
The diagram helps teams brainstorm and categorise potential causes, making it easier to identify root causes and develop targeted solutions.
The 6M categories for manufacturing
| Category | Typical causes to explore |
|---|---|
| Man (people) | Training and skills, experience, fatigue, communication, supervision |
| Machine (equipment) | Condition, maintenance status, calibration, age and wear, technology limits |
| Material | Raw material quality, supplier consistency, storage, specification compliance, contamination |
| Method (process) | Work procedures, process design, SOPs, process controls, documentation |
| Measurement | Accuracy, gage repeatability, data collection, inspection procedures |
| Mother Nature (environment) | Temperature and humidity, lighting, noise, cleanliness, weather |
How to create an effective fishbone diagram
- Define the problem clearly and specifically
- Assemble a diverse brainstorming team
- Identify the major cause categories (6M)
- Brainstorm potential causes for each category
- Ask “Why?” for each cause to reach root causes
- Prioritise and investigate the most likely causes with data
Best practices:
- Focus on causes, not symptoms
- Be specific and detailed
- Use data to support or rule out causes
- Include all team perspectives, and keep the session time-bound
- Follow up with an action plan for each confirmed root cause
Fishbone diagram applications
| Sector | Typical uses |
|---|---|
| Manufacturing | Product defects, equipment failures, process variation, quality projects |
| Service industries | Customer complaints, service delivery problems, system failures |
| Healthcare | Patient safety incidents, medical error analysis, process standardisation |
Worked example: defects in electronic assembly
An illustrative session on a high defect rate in a soldering cell. The team's candidate causes, one per category:
| Category | Candidate cause | How to check it |
|---|---|---|
| Machine | Soldering iron temperature drift | Log tip temperature over a shift |
| Material | Inconsistent solder paste | Compare defect rate by paste lot |
| Method | Inadequate work instructions | Review against the current process |
| Man | Gaps in operator training | Defect rate by operator |
| Environment | Humidity fluctuations | Overlay humidity log on defect timing |
| Measurement | Inconsistent inspection criteria | Attribute agreement study |
The diagram only generates hypotheses. The “how to check it” column is what turns it into a root cause analysis — confirm causes with data before acting.