Ishikawa-Fish for thought?

Overview

1.Fish bone diagram is a tool which is used to identify the root cause of the problem. The fish bone diagram is also called as Ishikawa diagram based on its pioneer Kaoru Ishikawa, a Japanese Engineering professor. He is noted for his quality management innovations and considered a key figure in the development of quality initiatives in Japan.

2.The defect is shown as the fish’s head with the causes extending as fishbones; the ribs branch off the backbone for major causes, with sub-branches for root-causes, to as many levels as required. The diagram is similar to the side view of a fish skeleton.

3. The year 1982 saw the development of the Ishikawa diagram, which is used to determine the root causes of a problem.

What is a fish bone diagram?

Fishbone diagram includes a central “spine” and several branches reminiscent of a fish skeleton. This diagram is used to identify all of the contributing root causes likely to be causing a problem. The Fishbone chart is an initial step in the screening process. After identifying potential root cause/s, further testing will be necessary to confirm the true root cause/s. This can be used on any type of problem and can be used to fit the events.

Applications

1.Fish bone is used as an investigational tool in finding out the root causes and taking corrective actions.

2.To find out the potential root causes of a problem in any field.

How to use the fish bone diagram?

When encountered with a complex or a difficult problem, brain storming the potential causes is always good but if it is not organized well, identifying the root cause becomes difficult and messy. So, fish bone diagram is one of the tools to do it in a structured way.

Step 1: Identify the Problem

First, note down the problem you have encountered. Write the problem in a box of a large sheet of paper, and draw a line across the paper horizontally from the box. This arrangement, looking like the head and spine of a fish, gives you space to develop ideas.

Step 2: Identify the major factors

Identify the major factors that may be part of the problem. These may be Man, Machine, Method, Measurement, Materials, Mother nature [6M’s]. The most commonly used is 6 M’s. The factors may vary depending upon the problem.

Step 3: Identify possible causes under the major factors

For each of the identified major factors, identify the possible causes of the problem that are related. These possible causes will be the shorter lines coming off the “bones” of the diagram. Examples are given below.

1.Man–This factor is related to the people associated with the process/problem.

• Operator did not complete the training.
• Employee could not physically see the defect.

2.Machine–This factor is related to the machine associated with the process/problem.

• Preventive maintenance schedule not followed.

3.Method–This factor is related to the method and instructions associated with the process/problem.

• Instruction not clearly defined in the SOP.
• Update not done for the procedure and still outdated.

4.Measurement – This factor is related to any techniques used to measure whether a part or process meets the desired quality standards.

• Measuring scale does not function correctly.
• Measuring gauge not calibrated.

5.Material-This factor is related to capture the materials involved in a given process.

• Part number of material used for the batch manufacturing does not match with the part number defined in the batch record.
• Material is expired.

6.Mother nature– This factor is related to the relevant external factors like environmental temperature, humidity or pressure.

• Excursion observed in temperature.
• Power failure in spikes.

Step 4: Brain storm the fish bone diagram

After the completion of the listing down the causes and effect, brain storm the fish bone diagram and start to investigate each cause by carrying out individual investigations, collecting data, carrying out survey to identify whether the possible cause listed out is contributing to the problem.

Example of one identified problem of ”Product yield decreasing with successive batches” and how the major factors and causes given in the fish bone diagram.

Advantages of using fishbone diagram

• It helps to identify the root cause of the problem/s.
• Useful for brain storming sessions/discussions.
• Brain storming sessions involves many schools of thought and ideas getting generated across.
• Can be coupled with 5 whys technique effectively in narrowing down the root cause/s.
• It helps to identify the root cause as well as to the contributing and underlying factors.

Disadvantages of using fishbone diagram

• Many irrelevant potential causes can come along and will take lot of time to rule out.
• Multiple factors and multiple causes are difficult to display in a fishbone diagram.
• Complex fishbone diagram will demotivate the investigation team.

Conclusion

Whenever regulatory authorities perform an audit of a drug manufacturer, the frequent findings are the inadequate performance of the investigation of deviations. The expectations are to carefully investigate the deviations such that the root cause is correctly identified and remedial actions in the form of CAPA [Corrective and Preventive Action] are taken.  If the root cause is not rightly identified, the implementation of CAPA and their effectiveness becomes a question and that is the sole reason for the occurrences of repeat deviation. Here comes the importance of “fishbone diagram” and the “5 whys”. These are the very effective tools in the RCA [Root cause analysis]. Regulatory authorities place a high value on RCA and CAPA.

When the members of the investigation team are uncertain on how to proceed or what information to take up to identify the root cause, this tool will certainly help to keep an open mind and focus on the facts. In the end, only the facts of a given investigation will provide the objective evidence that leads to the successful conclusion of an investigation. The other most common mistake of the investigation team is to jump to conclusions to find the root cause of an incident. The conclusion is allowed to drive the causes, rather than allowing the causes to drive them to the conclusion. Fish bone tool is highly appreciated by regulatory agencies when used effectively for the investigation of deviations.

Note-The images given for representation in this blog are taken from Google Images. Many thanks for Google.