1.1 CAUSE AND EFFECT DIAGRAMS
• Consider a production team about to launch a new product. They must anticipate factors that will affect the final product
APPROACH - Use a Cause and Effect Diagram
• The cause and effect diagram was developed by Kaoru Ishikawa in 1943.
- Commonly called - Cause and Effect (CE), Ishikawa Diagram or Fishbone diagram
• In quality we use these to find factors that have some role in a good/bad quality.
• For manufacturing there are some more standard causes to consider.
• How can a CE diagram be made up?
- use a team for more ideas
- use brainstorming techniques
• Brainstorming is a two stage process
Step 1: As a group, have each team member contribute ideas. If an idea is not good it doesn’t matter. Add ideas to the diagram. Exhaust all ideas! NO CRITICISM!!!
Step 2: Review the diagram critically as a group. Voting will help to narrow down what are the most important factors.
• What use is a CE diagram?
- Post it in visible spots for common reference by all the workgroups.
- Use it to anticipate, or find the cause of problems.
- Keeps workers involved and informed.
• Advantages of CE diagram
- Analysis - allows tracking of errors, efficient use of resources, lower costs.
- Elimination of unwanted causes.
- Standardization of existing and proposed operations.
- Education and training to allow personnel to make decisions and correct problems autonomously.
1.1.1 Process Diagrams
• Another type of CE diagram is the Process-Analysis diagram. This is used when there are a number of operations or factors involved.
• When considering CAUSES, there are two main types, assignable and chance.
chance - normal, or natural variations that occur in a system (e.g. dice)
assignable - controllable parameters such as material, process parameters, operator skill, etc.