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Quality Gurus & their contribution

Walter Shewhart Edward Demings Philip Crosby Joseph Juran Armand

Feigenbaum Kaoru Ishikawa Genichi Taguchi Shigeo Shingo James Harrington

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Contribution of Kaoru Ishikawa

Cause effect diagram (fishbone diagram)

Wrote book “Guide to Quality Control”

Wrote book “What Is Total Quality Control”

Father of the Quality Circle Movement

Quality Circle Problem solving methodology Concept of “Internal

customer”

Ishikawa Diagram (Cause-and Effect Diagram, Ishikawa Diagram)

Ishikawa diagrams (also called fishbone diagrams, Herringbone diagrams, cause-and-effect diagram or Fishikawa diagram) are causal diagrams created by Kaoru Ishikawa that show the causes of a specific event. Ishikawa diagrams were popularized in the 1960s by Kaoru Ishikawa.

It is considered one of the seven basic tools of quality control. It is known as a fishbone diagram because of its shape, similar to the side view of a fish skeleton. The fishbone diagram identifies many possible causes for an effect or problem. It can be used to structure a brainstorming session. It immediately sorts ideas into useful categories.

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Common uses of the Ishikawa diagram

Product design

Quality defect prevention Identify potential factors causing an overall effect.

Each cause or reason for imperfection is a source of variation.

Causes are usually grouped into major categories to identify and classify these sources of variation.

The defect or effect is shown as the fish's head, facing to the right, with the causes extending to the left as fishbones; the ribs branch off the backbone for major causes, with sub-branches for root-causes, to as many levels as required.

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When to use

When identifying possible causes for a problem. When a team’s thinking yields nothing and are stuck

Procedure

Materials needed: flipchart or whiteboard, marking pens.

1. Agree on a problem statement (effect). Write it at the center right of the flipchart or whiteboard. Draw a box around it and draw a horizontal arrow running to it.

2. Brainstorm the major categories of causes of the problem. If this is difficult use generic headings:

Methods Machines (equipment) People (manpower) Materials Measurement Environment

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3. Write the categories of causes as branches from the main arrow. 4. Brainstorm all the possible causes of the problem. Ask “Why does this

happen?” As each idea is given, the facilitator writes it as a branch from the appropriate category. Causes can be written in several places if they relate to several categories.

5. Again ask “Why does this happen?” about each cause. Write sub-causes branching off the causes. Continue to ask “Why?” and generate deeper levels of causes. Layers of branches indicate causal relationships.

6. When the group runs out of ideas, focus attention to places on the chart where ideas are few.

Advantages

Brainstorming technique which can be used to identify the root causes of some problem

Quickly identify if the root cause is found multiple times in the same or different causal tree

Allows one to see all causes simultaneously Good visualization for presenting issues to stakeholders

Disadvantages

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Complex defects might yield a lot of causes which might become visually complex

Interrelationships between causes are not easily identifiable

Root-cause analysis It is intended to reveal key relationships among various variables, and the possible causes provide additional insight. The causes emerge by analysis, often through brainstorming sessions, and are grouped into categories on the main branches off the fishbone. To help structure the approach, the categories are often selected from one of the common models shown below, but may emerge as something unique to the application in a specific case. Each potential cause is traced back to find the root cause, often using the 5 Whys.

Technique of 5 Whys The 5 Whys is a technique used in the Analyze phase of the Six Sigma DMAIC (Define, Measure, Analyze, Improve, Control) methodology. It is a great Six Sigma tool that does not involve data segmentation, hypothesis testing, regression or other advanced statistical tools, and in many cases can be completed without a data collection plan. By repeatedly asking the question “Why” (five is a good rule of thumb), you can peel away the layers of symptoms which can lead to the root cause of a problem. Very often the reason for a problem will lead you to another question. Although this technique is called “5 Whys,” you may find that you will need to ask the question fewer or more times than five before you find the issue related to a problem.

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Typical categories include: The 5 Ms (used in manufacturing) Originating with lean manufacturing and the Toyota Production System, the 5 Ms is one of the most common frameworks for root-cause analysis:

Man / mind power (physical or knowledge work, includes: kaizens, suggestions)

Machine (equipment, technology) Material (includes raw material, consumables, and information) Method (process) Measurement / medium (inspection, environment)

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The 8 Ps (used in product marketing) This common model for identifying crucial attributes for planning in product marketing is often also used in root-cause analysis as categories for the Ishikawa diagram:

Product (or service) Price Place Promotion People (personnel) Process Physical evidence Performance The 8 Ps are primarily used in product marketing.

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The 4 Ss (used in service industries) An alternative used for service industries, uses four categories of possible causes:

Surroundings Suppliers Systems Skill

Fishbone Diagram in Lean Objective of the lean or Six Sigma transformation is removing the clutter to reveal waste or opportunities for improvement. A fishbone diagram aims to break down and find out the Causes of an issue to reveal what elements have the greatest impact. Grouping the “causes” means you can think about the different elements of the problem as separate from the overall process. One or two of these “causes” will have a greater effect than the others and will guide you to the root of the problem. This structure also allows you to tackle smaller chunks which have a large impact on the problem. Looking at elements of the problem and not the whole process will likely make finding your solution less daunting and problem solving more manageable. After you have determined your root cause, prioritize or screen the causes to determine which are having the largest effect. Once identified focus on these. An

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easy Cause screening method involves looking at each one and asking two questions: How likely is this cause to be the major source of the issue or variation?

V - Very Likely S - Somewhat Likely N - Not Likely How easy would it be to fix or control?

V - Very Easy S - Somewhat Easy N - Not Easy

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