Assignment

Aim of method usage:
identify error determine weak spots ensure quality rate risk identify risk

Method classification:
Methods for analysis and aims

Process phase:
embodiment design detail design product planning

Useful links:

Glossary

Literature

Failure Mode and Effects Analysis

FMEA

With the FMEA it is possible to systematically and fully capture as well as predict possible problems, their risks and consequences before they actually occur.
Potential risks are uncovered and evaluated by an interdisciplinary group of people through utilization of past experiences and creative capabilities. They then reduce the risks by determining appropriate corrective measures and reevaluating their effectiveness.
The FMEA process can be run iteratively to check the results of the prior run. The results regulate the entire quality assurance process.

Possible goals for an FMEA can be
- the identification of critical components or weaknesses
- the timely recognition, determination, quantification and localization of possible flaws
- the exchange and transfer of knowledge and experiences
- the reduction of nonconformity costs i.e reducing the number of adjustments after the serial run.

Procedure

Determining goal and group:
The FMEA's goal is given in the form of a task by management. Depending on the task a group of experts from different departments is put together and a moderator is selected. A time frame is set when planning the general process.
Identifying possible flaws:
For each component within the system possible types of error are documented. The groundwork may be done through a system analysis (for example fault tree analysis).
Determining causes and effects of possible flaws:
Possible causes for mistakes and their effects are determined and documented. Any one mistake may have multiple causes. This step can also be completed through a fault tree analysis.
Evaluation of causes:
All identified mistakes are evaluated regarding A: likelihood of occurrence, B: the significance of the mistake for the customer, E: probability of detection before delivery to the customer is commenced; each criteria is awarded a value between 1 and 10. When evaluating the factors A, B, and E, a grid with a given downgrading may be used.
Calculating and analyzing the risk priority index (RPI)
By multiplying the three factors A, B and E one gets the RPI to assess the effects of possible mistakes: RPI=AxBxE
Generally, aspects that cause mistakes with a high RPI will be given priority when it comes to applying correective actions. The same applies to aspects with multiple causes where a single factor already exceeds 8. It has been proven effective to apply the RPI as follows:
RPZ < 100: Okay if the group also accepts the RPI's individual ranking.
100 < RPZ < 200: Decision shall be at the discretion of the group and their reasoning is to be noted on a blank form.
RPZ > 200: measures required
Determination of measures in error correction:
In this step measures for error correction are determined. They should aim at reducuing the RPI of possible errors.
Analysis after employment of measures:
After employing the corrective meaures, another cycle of determining error occurrence, significance and detection is run and the new RPI calculated (repeat step 4 and 5). By comparing the potential for improvement and the cost assessment for the measures, it is possible develop a suitable procedure for error minimization.

Strengths and weaknesses

Strengths	Weaknesses
preventing mistakes support of interdisciplinary cooperation at an early stage of product development gathered knowledge can be evaluated regarding quality assurance measures	determining functions and matching errors is a complex tasks for unfamiliar systems time consuming if the method cannot be restricted to subsystems

go back

zur Startseite