7QC Tools: Fish Bone or Ishikawa DiagramAmrendra Roy
Once we have prepared the process flow diagram, we need to list down the possible causes of a problem graphically so that everyone can understand. The Fish Bone diagram is a graphic tool that helps in displaying the possible causes of a problem or quality characteristic.
Usually Fish Bone diagram is also called as Cause & Effect diagram, but I beg to differ here as Fish Bone diagram only gives the list of probable causes that may or may not affecting the quality parameter. Hence, I take it as a misnomer. The reason being, we need to establish the Cause & Effect relationship downstream using scatter plot or Design of Experiments and only after that we can say cause & effect relationship is established.
The Fish Bone diagram helps in listing down the possible causes of variation through group discussion. It presents the list in a pictorial form, which is easily understandable, it also increases process understanding and tells us to collect the data for possible causes of variation.
It also categorizes the all possible causes of variation in 5 broad categories known as 5M
Men (problem because of people)
Material (problem because of raw material)
Machine (Problem due to Machine)
Methods (problem due to the measurement system or the process)
Management (problem related to management)