Stop failure in its tracks
by Dorothy Lueck, CIRAS
Failure Mode and Effects Analysis (FMEA for short) is a systematic way to recognize and evaluate the potential failures of a product or process. It provides a formal mental discipline for eliminating or reducing the risks of product failure. It also serves as a living document, providing a method of organizing and tracking concerns and changes through product development and launch.
FMEAs were developed in the 1960s by the aerospace industry during the Apollo program and were later adopted by the automotive industry as a required component of the advanced quality planning process. In the automotive industry, FMEAs have been applied to vehicle systems, subassemblies, and components.
The best time to start the FMEA is before a failure is designed into a product or manufacturing process. FMEAs help reduce crises during product development and launch and thus reduce costs, since early, up-front changes tend to cost less than late, downstream ones. The corrective action review and evaluation can avoid creating new concerns, and the cost impact of changes can be evaluated during development. FMEAs can also be used to develop new equipment or to evaluate the operations of existing equipment and systems.
FMEA is an interactive process of continuous improvement that involves team effort. Functional areas involved include design, materials, manufacturing, assembly, packaging, shipping, service, recycling, quality, reliability, vendors, and customers. Customers include, but are not limited to, downstream engineering functions, downstream manufacturing functions, end users, service functions, and recycling or reuse functions. Two types of FMEAs are used by the automotive industry: potential failure mode and effects analysis in design (Design FMEAs), and potential failure mode and effects analysis in manufacturing and assembly processes (Process FMEAs).
Design FMEAs are based on product design elements. Block diagrams form the basis for the Design FMEA. Block diagrams model the elements of product design, indicating the flows of inputs, functions, and outputs involved. The Design FMEA addresses the design intent and assumes that the design will be manufactured or assembled accordingly. The Design FMEA does not rely on process controls to overcome potential design weaknesses but takes into consideration technical and physical limitations of manufacturing and assembly processes.
Process FMEAs are based on manufacturing or assembly processes used to make the product. Process flow diagrams and risk assessments form the basis for the Process FMEA. Process flow diagrams illustrate the flows of the manufacturing and assembly processes, the inspection points, and the processes for handling non-conforming material. Risk assessment is used to determine high risk parts of the process. The Process FMEA assumes that the product as designed will meet the design intent.
Both Design and Process FMEAs address three issues for each potential failure mode: the severity of the effect of the failure downstream, the probability of occurrence of the failure, and the likelihood of prevention or detection of the failure by design or process controls. Rankings based on ordinary scales from one to ten are used.
If you are developing a new product or process, give CIRAS a call for assistance in developing your FMEA.
CIRAS News, Vol. 31, No. 1, Fall 1996