D-FMEA : Introduction

Introduction to D-FMEA

FMEA is an acronym for Failure Mode and Effects Analysis. If the subject of such analysis is a product design, we refer to it as a design FMEA or a construction FMEA. In English, it is referred to as "Design FMEA" or "D-FMEA" for short.

Independent of "official definitions," it can be said that D-FMEA is a method for systematically identifying failure modes (malfunctioning product) and the effects on customers. The causes are then identified, ultimately understood as design flaws - that is, incorrectly specified product characteristics. The following example illustrates just this idea:

The risk level is then estimated based on three indicators:

• S - Severity of the effects of the failure mode
• O - Occurrence of causes of the failure mode
• D - Ability to detect a given failure mode / cause during the design process

For each indicator (S, O, D) a value from 1 to 10 is assigned according to special ranking tables.

The "level of risk" is then assessed. Depending on the rules chosen, it could be:

• RPN - is the Risk Priority Number. RPN is calculated as the multiplication of the indicators S, O and D.
• AP - Action Priority. Selected on the basis of a special table and the values of the S, O and D indicators.

In case of high risk values (high RPN or AP rate), we shall try to implement appropriate measures to reduce the risk.

The D-FMEA method is very useful during the design of products for its evaluation for correct performance of required functions in the intended operating environment and assumed service life. It can be applied to both physical and software product design in any industry. D-FMEA can also be used when designing a "service delivery process."

Does it work?

Correct application of D-FMEA speeds up project execution and increases the chances of market success, because we can spot problems in the design and correct them before deployment to production. This reduces the number of "iterations" in the project, thus effectively reducing design time.

The key word in the above sentence is "correct application" - that is, if we do the analysis at the right time (very important), with the right approach (also very important), do it "for us" and not "for the client/auditor", then we get a kind of project overview with a list of risky or even wrong design decisions. This means saving $$$, of course, if we implement some sensible actions to reduce this risk.

If, in a given company, D-FMEA is seen by designers as a waste of time, the designers are probably right.... and in fact it may be a "waste of time" because the method is simply poorly implemented.

For whom is the D-FMEA?

D-FMEA is for people who design a product.

When start the D-FMEA?

D-FMEA is launched at the early stage of the design process, when the product concept is formed. Even then, much of the data for analysis can be established. Keep in mind that the D-FMEA is an integral part of the design process and is to be completed regularly as the project evolves.

Management responsibility

The role of management is critical to the successful implementation of D-FMEA. Resources should be provided (personnel, time, space, training, tools), determine who is responsible for the D-FMEA (usually the lead product designer), oversee the implementation of improvement actions, etc. This responsibility should not be shifted to the quality department or external consultants..

Main steps of D-FMEA

Depending on the standard used, there are some differences in the implementation of D-FMEA, but typically we can identify the following major steps:

• Establish the D-FMEA implementation team. This team should be multidisciplinary. The team leader is the person responsible for the design of the product in question.
• Determine the scope of the analysis, dividing the project into subsystems/components. The level of detail and the principles of partitioning depend on the ground rules adopted.
• Using tools such as interaction matrix, p-diagram to better understand the factors affecting product performance and reliability.
• Identification of functions and requirements.
• Identification of failure modes (defects) understood as failure to meet functions/requirements.
• Estimation of the effects (consequences) of failure modes on customers.
• Identification of potential causes of failure modes.
• Identification of prevention and detection methods.
• Estimation of the values of indicators: S, O, D and determine the level of RPN/AP risk.
• Identify risk-reduction measures where possible.
• A re-assessment of risk after the introduction of measures.
• Preliminary identification of possible special characteristics (depending on the company's procedures).
• Refine / update the DVP prototype validation plan.
• Update D-FMEA influenced by DVP test data, complaints from the market, etc.

D-FMEA standards

There are several standards / manuals that define how to conduct D-FMEA. For example:

• AIAG FMEA
• VDA FMEA
• AIAG-VDA FMEA
• SAE J1739
• Specific methods of some vehicle manufacturers (OEMs): Ford, PSA, Renault, etc.
• ISO-60812
• ISO-16602
• Others

If we can freely choose the standard, I personally prefer AIAG FMEA-4 (I know it's "old", but very easy and popular) or the very cool SAE J1739:2021 (the latest edition, related to AIAG-VDA FMEA). These methods can be implemented relatively easy without the need to purchase specialized software, and if implemented correctly, can be very effective.

The AIAG-VDA FMEA method, which is now (2023), required by most automotive OEMs, can also be used, however, for complex processes it is difficult to use it effectively in a spreadsheet. In that case, good software will be recommended.

AIAG-VDA FMEA also has some "nuances" that can lead to less effective results.. but that's a topic for another article ;)

Feel free to read a short article: History of FMEA.

Summary

The D-FMEA method is a very useful tool during product design. It allows to methodically evaluate the design for correct realization of the required functions in the specified operating environment and assumed service life. It can be applied in the framework of physical product design as well as software development. D-FMEA is useful in any industry.

Correct application of P-FMEA significantly reduces costs and improves product quality. This method should be an aspect of great importance to company management.