This method is called a “cause and effect” diagram, or Ishikawa diagram, known as a “fishbone.” We have used the fishbone and found that it allows the JHA developer to list all of the elements of the job as well as all of the tasks as they relate to specific steps. The method provides a visual picture of what we are trying to say. Using the example of changing a tire, as presented in Chapter 7, we now will provide a method to break down the task of changing a tire into manageable pieces. I have used this method, working with four line operators to identify and make a simple process modification that cost £450 to implement and saved £450 per week every week and is still saving £450 per week to this day. Real cause and effect charts will be more complex and have more details on the main branches as well as scores for the relative importance of the cause in the creation of the effect or methods for checking the importance of the cause. These are for a production environment (general plastic parts) and for a service environment (installation of PVC-U windows). Two examples of cause and effect charts are shown on the right using the M’s and the P’s. Studies of current production using check sheets (see Section 7.3), scatter diagrams (see Section 7.7) or capability studies (see Section 5.4).Īfter the important causes are identified the team can start to develop the methods and actions to minimise or maximise the effect. The people doing the ranking should know what is really happening in the process.Īnalysis of past data using Pareto analysis (see Section 7.5). Use the employee’s knowledge to identify the most significant or likely factors and to rank these on a 1 to 10 scale. Tip - Use Post-it notes as part of the process (CEDAC) because they can be moved around easily as the diagram is developed. Look for root causes that appear in more that one major cause category. Often some of the initial causes identified are actually symptoms of another cause. Probe to seek the ‘root cause’ rather than simply accepting that everything is a cause. Tip - The major cause headings are not sacred and you can change these to reflect the particular effect that you are seeking to minimise or maximise. Group the ideas into logical branches of related causes. Tip - Try not to censor ideas at the brainstorming stage. Tip - It is essential that the people making the diagram know what really happens in the process and are not completing the diagram as if it is an ideal world. Brainstorming techniques or previous lists generated by the team can be used to quickly generate a list of possible causes. Using the basic frameworks as a guide, use the employees involved with the process or service to identify the various causes that are likely to create the concern. It is important that the team is in agreement that this is the real concern and that it is not simply a symptom of the real effect. Using a flip chart, the concern or effect is drawn to the right of the major fish bone as the ‘fish head’. This could be from Pareto analysis, check sheets or any other method. Select a concern identified as being significant. The best way to gain value from the cause and effect diagram is to:

Ishikawa diagram for manufacturing