2) machinery process variation that can be described in terms of something that can be corrected or can be controlled.
Identification of causes should start with those failure modes with the highest severity rating.
Review historical test reports, warranty data, concern reports, recalls, field reports, and other applicable documents listed in Appendix II. Also review surrogate FMEAs. List the known causal factors of the failure modes listed in Column 14.
Brainstorm potential cause(s) of each failure mode by asking questions, such as:
What could cause the subsystem to fail in this manner?
What circumstance(s) could cause the subsystem to fail to perform its function?
What can cause the subsystem to fail to deliver it intended function?
Identify all first level causes. A first level cause is the immediate cause of the failure mode. It will directly make the failure mode occur. In a Cause and Effect Diagram, it will be an item on the major �fishbone� of the diagram. In a Fault Tree Analysis (FTA), it will be the first cause identified below the failure mode.