Failure Mode And Effect Analysis (fmea)

For years, failure modes and effects analysis (FMEA) has been an integral part of engineering designs. For the most part, it has been an indispensable tool for industries such as the aerospace and automobile industries. US government agencies (i.e. Air Force, Navy) require that FMEA’s be performed on their systems to ensure safety as well as reliability.

A Failure Mode and Effect Analysis (FMEA) is an engineering technique used to define, identify and eliminate known and or potential failures, problems, errors from the system, design, process and or service before they reach the customer. It is s a systematic approach and

a mental discipline that an engineer normally goes through in any manufacturing process. It is also problem prevention tool and a living document of engineers’ thoughts based on experience, past concerns and quality performance indicators. FMEA is an established reliability engineering activity that also supports fault tolerant design, testability, safety, logistic support, and related functions. The technique has its roots in the analysis of electronic circuits made up of discrete components with well-defined failure modes. FMEA is “a systematic, analytical approach to properly plan for defect prevention and mistake-proofing. It is a technique for identifying and focusing on those areas in the design and manufacturing process for the prevention, reduction, and elimination of non-conformances in the product or production”. The Failure Modes and Effects Analysis (FMEA) is a document to identify the associated with something potentially going wrong such as creating a defect or out of specification) in the production of the product. The FMEA identifies what controls are placed in the production process to catch any defects at various stages on the processing.

What can be achieved with FMEA?

1. Recognize and evaluate the potential failure of a product/ process and the effects of that failure
2. Identify actions that could eliminate or reduce the chance of the potential failure occurring, and
3. Document the entire process.

The main objectives of a good FMEA includes the identification and evaluation of potential failure modes that could occur in design and in manufacture of products. It is also use to identify causes and actions that could eliminate or reduce the changes of the potential failure occurring. And lastly, it is used to identify and document the process and its characteristics. Analyze the design characteristics relative to the planned manufacturing process to ensure that the resultant product meets customer needs and expectations. It provides an organized, critical analysis of potential failure modes of the system being defined and identifies associated causes. Most notably, it was the automotive industry that has adopted FMEA’s in the design and manufacturing/assembly of automobiles. Although there are many types of FMEAs (design, process, equipment) and analyses vary from hardware to software, one common factor has remained through the years—to resolve before they occur.

There are three basic types of FMEA. The Design FMEA which helps eliminates design-related failures (new designs, new technology, or new process). The scope of the FMEA is the complete design, technology, or process. The Process FMEA which helps eliminates failures that result from changes in process variables. Modifications to existing design or process (assumes there is an FMEA for the existing design or process). The scope of the FMEA should focus on the modification to design or process, possible interactions due to the modification, and field history. And the Service FMEA which helps eliminates product failures due to improper installation, operation, maintenance and repair. Use of an existing design or process in a new environment, location, or application (assumes there is an FMEA for the existing design or process). The scope of

the FMEA is the impact of the new environment or location on the existing design or process.

Design FMEA.A Design FMEA is a disciplined analysis or method of identifying potential or known failure modes and providing follow-up and corrective actions at the design stage. Design FMEA is a Living Document Initiated before or at design concept finalization. Continually updated as changes occur or additional information is obtained throughout the phases of product development. To make a Design FMEA one must develop a list of what the design is expected to do and what it is expected not to do. He should be able to determine the customer wants and needs and the product and manufacturing requirements should be incorporated. Design FMEA should begin with a block diagram for the system, subsystem and or component being analyzed. This block diagram can also indicate the flow of information, energy, etc.

Process FMEA. The main purpose of a Process FMEA is to produce a product that meets all specification every time. It identifies the potential deviations from specification, and eliminates or minimizes them by preventing or detecting change in the process variables. In making a Process FMEA one should begin with process flowchart and perform a risk assessment of the general process. This flow chart should identify the product or process characteristics associated with each operation. Also, identification of some product effects from the corresponding DFMEA should be included.

Team Effort. Although responsibility for the preparation of the FMEA is usually assigned to an individual, FMEA input should be a team effort. A team of knowledgeable individuals should be assembled (e.g., engineers with expertise in design, analysis/testing, manufacturing, assembly, service, recycling, quality and reliability). The Process FMEA should be a catalyst to stimulate the interchange of ideas between the areas affected and thus promote a team approach.
Customer Defined. The definition of “Customer” for a Process FMEA should normally be the “End User.” However, the customer can also be a subsequent or downstream manufacturing or assembly operation, a service operation, or government regulations.

Product Design. The Process FMEA, assumes the product as designed will meet the design intent. Potential failure modes that can occur because of a design weakness may be included in a Process FMEA. Their effect and avoidance is covered by the Design FMEA. The Process FMEA does not rely on product design changes to overcome weaknesses in the process. However, it does take into consideration a product’s design characteristics relative to the planned manufacturing or assembly process to assure that to the extent possible, the resultant product meets customer needs and expectations.

Timeliness. FMEA is to be a “before-the-event” action, not an “after –the-fact” exercise. To achieve the greatest value, the FMEA must be done before a product or process failure mode has been incorporated into a product or process.


References
- Failure Mode and Effect Analysis Manual, 3rd Edition, AIAG

- J1739, Potential Failure Mode And Effects Analysis, SAE

- MIL-STD-1629, Procedures for Performing a Failure Mode, Effects and Criticality Analysis


note: originally posted at Bukisa.com under the same author.



Article Written By joeldgreat

Where I belong...New ways to contribute to humanity by posting relevant blogs and articles. Back from the grave..

Last updated on 08-07-2016 108 0

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