Problem Solving & Ishikawa

Last month I was asked by one of our clients"Where do Global 8D, Ishikawa and Brainstorming fit into the problem solving effort?"

A simple enough question, so I thought I would share the answer as this maybe something that someone else may like to know!

Global 8D (G8D)

G8D is widely recognised throughout the Automotive, Aersopace and Pharma industries as a leading edge methodology. However, this tool should be reserved for a small number of problems (normally less that 5% of all problems), which typically require more than one person to resolve, are complex in nature and whose cause is unknown. Also, because of the nature of this methodology, the resource needed to solve the problem would be less than the cost of the problem (or the effects of the problem).

For the majority of problems G8D is more than is required, however some of the techniques used are useful from time to time e.g. Is / Is Not Analysis, Differences & Changes, Root Cause Theory as part of Root Cause Analysis.

Ishikawa And Problem Solving

Ishikawa diagrams (also known as Fish Bone diagrams) are most commonly associated with problem solving.

However Ishikawa is widely used alongside other tools and processes, including but not restricted to:

• Problem Prevention (Design FMEA, Machinery FMEA)
• Risk Assessment
• Problem Solving (Global 8D, 5WHY's, Root Cause Analysis)
• SWOT Analysis
• Business Planning
• Fault Tree Analysis (FTA)

In problem solving terms, the Ishikawa diagram is used to organise the output of a brainstorming session

The brainstorm is about establishing possible root causes to a problem that has been fully described (by this I mean we know what is wrong with what!), the problem description to root cause analysis phase

Be careful not confuse the problem with the effect, its the problem we need to solve, NOT the effects of the problem

Ishikawa (Fishbone) Diagram And Root Cause Analysis

Problem solving is a process of elimination through the use of data and analytical tools, driven by clear logical thinking.

The effect or symptom is what is experienced, this is caused by the problem, which in turn has a root cause.

To establish the root cause we first have to ensure we fully describe the problem using facts. The cause is determined in three levels, as seen in this diagram, and Possible Causes are the output of a brainstorming event.

We use the Ishikawa diagram to give the brainstorm  some order. Common 'bones' are Man, Equipment, Machine, Environment and Material (MEPEM). The brainstorm output would be placed against each 'bone' (see diagram below). 

In Problem Solving terms, the next stage woul be to ask 'WHY?' for each possible cause until you can go no further. Once you have considered this final answer (5 WHY's), established that the causal theory explains why the problem occurs only on the affected items, then you will have a potential root cause.

A causal theory is a statement that describes how a potential root cause initiates the problem and the effect experienced.

Example:

Problem Scenario: Every time I leave my car for more than a day without running the engine, it will not start

Problem Description: Car will not start

Possible Cause: Faulty battery

Causal Theory: The battery does not hold a charge for more than 24 hours. Over time there is not enough power to operate the starter motor so the car will not start.