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By Benjamin Moses, Technical Director at AMT – The Association For Manufacturing Technology, which owns IMTS – The International Manufacturing Technology Show

Known alternately as the fishbone, fish skeleton, herringbone, cause and effect, and 5M, the Ishikawa diagram is a dispersion analysis that graphically displays causes to a problem/effect. This tool has been used since it became popular in the 1960s. Like other problem-solving tools, the Ishikawa diagram will only aid in the management and structure of getting to the resolution. The process of creating and maintaining this tool is straightforward.

The fishbone diagram begins with the problem statement (effect) at the head. This is not the easiest item to determine. The tools to create a problem statement are five Whys and observational analyses. The spines of the fishbone diagram (causes) are then defined. This is based on the application. Most manufacturing problems are grouped into the following categories: Man (people), Method (process), Machine (equipment), Measurement, and Material. Environment may be a factor in some processes such as welding or precision manufacturing. Details of each cause are added. Brainstorming, then categorizing, aids in the process. 

The next step is to further understand what can be controlled. Noise is defined as a variable that can’t be controlled. Control is a variable that can be changed on demand. The starting point for further investigation is labeling each cause as control or noise. Causes can be investigated for in or out specification during the manufacturing process, or tested on sample pieces and completed by single elimination or a design of an experiment if there is a risk of interactions. Observational analysis will help document the testing and once the major contributors are found, they can be changed and controlled in the future.

This tool has several pros and cons:

Pros

  • Visual
  • Builds consensus
  • Robust
  • Repeatable
  • Tracks progress
  • Can be used in a variety of scenarios
  • Resolution of causes scales with complexity

Cons

  • Requires time
  • May require more than one person
  • May require further investigation

This tool can be used in a variety of settings and scenarios. These include sales and marketing, business organization, design engineering, and personal development. There are a variety of aids for this tool:

Juran’s Quality Handbook, page 551

LucidChart Template: http://bit.ly/2iUabVA

Mindjet MindManager has an embedded template


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