Root Cause Analysis (RCA) is a method or series of
actions taken to identify the reasons why a particular failure or problem exists
and to highlight alternative solutions to eliminate the sources of those
problems. An analysis of the comparative benefits and cost-effectiveness of the
alternative solutions aids the decision maker in implementing the most
beneficial course of action. RCA goes beyond identifying resolutions for the
symptoms of a problem. It aims to provide solutions to eliminate the root cause
of the problem to ensure that the problem can never occur or recur.
The use of RCA is a systematic process of gathering all
relevant data about a problem, including its internal causes. When a problem
occurs, there are several ways it can be addressed. A common method is to
resolve the symptoms of the problem and hope it does not occur again. The
preferable method, however, is to get to the root cause of the problem and
permanently eliminate it. RCA is used to determine the root cause and to present
the decision maker with alternatives that can be analyzed to determine the
With regard to producibility, performing RCA can help
identify sources of problems that can be designed out of the final design,
thereby reducing rework and improving quality in production. Root cause analysis
can also be used to determine causes of problems in manufacturing - causes of
process variation or product quality problems.
The process for root cause analysis entails first
defining the specific problem to be addressed and then defining each mode in
which the problem occurs. Data is then collected, and the analysis of the
problem begins by defining the hypotheses of how the various failure modes could
have occurred. Next comes the verification of the hypotheses to identify which
failure mode was responsible for the problem. The results are tracked until a
final conclusion as to the root cause of the problem is determined.
Cause and effect diagrams, sometimes called fishbone
diagrams, are used to help identify the causes of a problem. An example of a
fishbone diagram is shown in Figure
F.6. The objective is to resolve the
problem, or effect, by performing a thorough investigation of all of its
possible causes. The effects are the particular quality characteristics or
problems that are being encountered, such as "heat" in the example below. The
causes are the factors that influence the stated effects, such as, in this case,
the material, equipment, operating methods, operators, or environment.
Typically, in manufacturing, problems or effects can be related to quality,
process variability, cost, schedule, safety, etc.
Throughout the process of developing the diagram, the use
of brainstorming sessions can help lead to new ideas that can help better
understand and identify the actual root cause of the problem.
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