Design and Technology – Quantity production | e-Consult

A Fishbone Diagram, also known as an Ishikawa Diagram or cause-and-effect diagram, is a visual tool used to identify and categorize the potential causes of a specific problem. It's structured like a fish skeleton, with the 'head' representing the problem and the 'bones' representing the major categories of potential causes. The diagram helps teams brainstorm and organize potential causes in a structured manner.

Key elements of a Fishbone Diagram:

• Head (Problem): The problem being analysed is placed at the 'head' of the fish. Example: "High defect rate in the widget assembly process."
• Bones (Categories): Major categories of potential causes are represented by the 'bones' branching off from the main spine. Common categories include: Manpower (People), Methods (Processes), Machines (Equipment), Materials, Measurement, and Mother Nature (Environment). The specific categories used will depend on the problem being analysed.
• Sub-Bones (Specific Causes): Within each category, specific potential causes are listed as 'sub-bones' branching off from the main bones. Example: Under the 'Machines' category, sub-bones might include "Lack of maintenance," "Inaccurate calibration," "Machine malfunction."

How it's used in a Kaizen process:

1. Define the Problem: Clearly state the problem to be addressed (e.g., high defect rate in widget assembly).
2. Identify Categories: Determine the relevant categories of potential causes (e.g., Manpower, Methods, Machines, Materials).
3. Brainstorm Causes: Within each category, brainstorm potential causes. Encourage diverse perspectives from team members.
4. Organise and Structure: Arrange the causes on the Fishbone Diagram in a logical and structured manner.
5. Analysis and Prioritisation: Analyze the diagram to identify the most likely causes of the problem. Prioritise these causes for further investigation.

Example: Applying a Fishbone Diagram to a Manufacturing Issue (e.g., inconsistent widget dimensions):

The Fishbone Diagram would have the 'High defect rate in widget dimensions' at the head. The bones would be labelled 'Manpower', 'Methods', 'Machines', 'Materials', 'Measurement', and 'Environment'. Under 'Machines', sub-bones might include: 'Lack of machine maintenance', 'Inaccurate machine calibration', 'Wear and tear on machine parts'. Under 'Materials', sub-bones might include: 'Variations in raw material dimensions', 'Poor quality of raw materials'. By analysing the diagram, the team could identify that 'Inaccurate machine calibration' and 'Poor quality of raw materials' are the most likely causes and focus their efforts on addressing these issues.