What does E stand for in FEMA

FMEA - Failure Mode and Effects Analysis

FMEA types and selection

The failure mode and effects analysis, FMEA for short (sometimes also FMEA analysis), is an analytical method of quality management for the development-accompanying risk analysis of failure prevention. The aim is to identify, eliminate or at least limit potential error causes and sources of error at an early stage. This active error prevention can achieve significant cost savings along the product life cycle.
To this end, possible production errors are identified and assessed. The errors are assessed with regard to their significance for the customer, the likelihood of their occurrence and the likelihood of detection before delivery to the customer. On the basis of this risk assessment, a decision is made as to whether measures to prevent errors are necessary.
The FMEA was originally called failure mode and effect analysis (sometimes too: failure mode, effects and critical analysis - fmeca) developed during NASA's space program in the 1960s. Due to the massive risks and the long development periods, the importance of preventive error avoidance in space travel cannot be high enough.

The FMEA should not be confused with the 8D report. This is also a troubleshooting process. However, the 8D report is a method for the analytical development and documentation of the long-term elimination of a defect. The 8D report is therefore a reactive problem-solving process that is used when the deficiency has actually already occurred. (For more information on repeating errors and the 8D report, please click here.)

As already emphasized, the primary goal of an FMEA is to identify errors at an early stage. In practice, a distinction is made primarily between the system, construction and process FMEA types. It is therefore important that you define the type of FMEA to be carried out at the beginning.

The system FMEA focuses on the functional interaction of the individual components of a complex system. Attempts are made to avoid errors in the system design and to check the functionality and security of the system. Construction FMEAs are specifically designed for a product. Potential errors and failures that can occur in parts or assemblies of a system are considered and an attempt is made to avoid them. The main cause of the error is the design, but also the type of production. The process FMEA basically examines all factors and persons responsible that could affect a fault-free process. Above all, the manufacturing and assembly process is considered.

When selecting the FMEA, it is recommended to proceed from the system to the individual. This means that first the entire system is considered in an FMEA, then its subsystems and assemblies. Furthermore, it is possible to carry out the FMEAs more and more precisely by looking at individual components. Finally or in addition, the associated processes can be examined.

The 6 steps of an FMEA

In the following, the individual steps of an FMEA are shown simply and briefly using an example. The construction, process and system FMEA are based on the same principle:

Step 1: preparation

In preparation, a team is first formed that is familiar with the method and implementation of an FMEA. The determination of a team leader with FMEA experience is helpful here. The definition of the task and objectives of the FMEA follows. In addition, all necessary documents and FMEA forms must be prepared.

Step 2: structural analysis

In the first step, the structure of a product or process is described in order to be able to get an overall picture. For this purpose, system elements are recorded. Each system element can be composed of other system elements. These elements are then combined into a structure and displayed graphically.

Step 3: functional analysis

All of the elements from step 1 have different functions or tasks. These are collected in the second step and assigned to the individual system elements.

Functions can have a relationship with one another. This can be well represented in a function network.

Step 4: failure analysis

The functions from step 2 now serve as a starting point for determining which errors could possibly occur. In the FMEA form, all potential errors are documented with their consequences and causes. This happens initially regardless of how serious or how likely the individual potential errors are. The risk assessment is only carried out in the next step.

Errors can also be networked with one another. A failure network that has already been used in the functions is again suitable for this. This network can also be used to link errors in such a way that the causes and consequences of the error can be clearly identified.

Step 5: Risk assessment using the risk priority number - RPN

During the risk assessment, the significance of each individual potential error of the FMEA is assessed in order to assess whether measures for improvement are necessary. The evaluation of the errors, as well as the prioritization for the elimination of the error causes, takes place via the risk priority number RPZ (also risk priority number). The risk priority number must be documented in the FMEA form for each defect. The higher the RPN, the sooner action should be taken to eliminate the cause of the error. The risk priority number is determined as the product of three factors, which could be evaluated as follows:

B = meaning of the failure consequence
The effect of the error is determined by (1), the error has no noticeable effect and is unlikely to be noticed by the customer, until 10), extremely fatal error that may affect security or regulatory compliance, rated.

A = probability of occurrence of the error
The probability that the error occurs is given by (1), it can almost be ruled out that the error will occur, until 10), it is almost certain that the error will occur regularly, rated.

E = probability of detection of the error,before the error reaches the customer
The likelihood that the bug will be discovered before it reaches the customer by (1), the error is inevitably discovered, until 10), a discovery of the error before handover to the customer is excluded, rated.