FMEAFailure Mode and

Effects Analysis

Andreea Precup

FMEA History• First used in the 1960s in the US Aerospace

Industry by NASA in the Apollo program (“It is a procedure for analysis of hardware items to determine those items contrbuting the most to system unreliability and crew safety problems.”)

• In the 1970s the Automotive Industry was driven by liability costs to use FMEA

• Later, the Automotive Industry saw the advantages of using this tool to reduce risks related to poor quality

What is FMEA?

FMEA is an analytical methodology used to ensure that potential problems have been considered and addressed throughout the product and process development process.

FMEA is a tool for risk management and continual improvement. It is a key part of APQP.

Types of FMEA

• Product (Design) FMEA• focuses on part function, on the design of the product• does not rely on process controls to overcome

potential design weaknesses, but it does take the technical and physical limits of the manufacturing process into consideration

• Process FMEA• focuses on the manufacturing steps of the product

Process FMEA

When to conduct a PFMEA?

• when new products/processes are being designed

• when existing designs or processes are being changed

• when existing designs are used in new applications

• periodically throughout the product/process lifetime

• in case of field issues or production issues the rankings should be revised

Identify the team

Define scope and criticality limits

Identify functions, requirements and specifications

Identify potential failure modes

Identify potential effects assess the SEVERITY level

Identify potential causes assess the OCCURENCE level

Identify current controls assess the DETECTION level

Calculate the Risk Priority Number and assess according to criticality limits

Establish recommended actions where in order, assign provisional ratings. After actions implementation, check efficiency and give final ratings. If satisfactory, FMEA is completed, if not further actions are

needed.

PREPARATION

FMEA Team

• cross-functional

• team leader should be expert in FMEA process

• team members need to have deep knowledge of the product and process to be analysed

• Quality Management representative will represent the customer

SCOPE AND CRITICALITY LIMITS

• Scope: establishes the boundary of the analysis, it defines what is included and excluded

• Criticality limits: at what level of risk actions to decrease it are required

FUNCTIONS, REQUIREMENTS AND SPECIFICATIONS

Identify and understand the functions, requirements and specifications relevant to the defined scope. The purpose is to clarify the item design intent or process purpose.

Input data is gathered: e.g. product definition and specifications, special characteristics, temporary process definition, process flow chart.

ANALYSIS

Process FMEA considerations

• the product as designed will meet the design intent

• the incoming parts/materials are correct

• failure modes can, but will not necessarily occur

POTENTIAL FAILURE MODE

The manner in which the process could potentially fail to meet the requirements.Needs to be described in technical terms.

Each function may have several failure modes:

- absence- stop- degraded

- intermittent- unconvenient- unplanned

POTENTIAL EFFECTS

The effects of a failure mode as perceived by the customer.Several effects may be identified for a failure mode, but for the purpose of the analysis only the worst case should be considered.

SEVERITY

An assessment of the level of impact of a failure on the customer

POTENTIAL CAUSES

An indication of how the failure mode could occur.Only specific errors or malfunctions should be listed, no ambuguous phrases should be used.Several causes might be identified. Each should be treated on a separate line.

OCCURENCE

Likelihood that the cause of a failure mode will occur

CURRENT CONTROLS

Those activities that prevent or detect the cause of the failure mode or the failure mode.Can be focused on: - prevention (eliminate or reduce occurennce)

- detection (identify associated CAs)Controls focused on prevention will provide the greatest return.

DETECTION

An assessment of how well the current control scheme can detect the cause of the failure mode

ASSESSMENT

Risk Priority Number (RPN)

RPN = S x O x DRPN ranges from 1 to 1000.

RPN is used to prioritize concerns/actions. The greater the value of the RPN, the greater the concern.

RECOMMENDED ACTIONS

The intent of these actions is to reduce the overall risk and the likelihood that the failure mode will occur.

In general, preventive actions (reducing the occurence) are preferable to detection actions.

• Reduce SEVERITY ranking: only a product design revision can reduce the S ranking

• Reduce OCCURENCE ranking: by removing or controlling one or more of the causes of the failure mode through a process design revision

• Reduce DETECTION ranking: error proofing or a redesign of the detection methodology. Increasing the frequency of inspection is usually not an effective measure and should only be used as a temporary measure until permanent preventive/corrective actions can be implemented

MGIC ACTIONS PRIORITIZATION

1. S = 10 actions to reduce O and D to 1

2. S = 8 or 9 actions to reduce RPN to 50

3. Criticality above the one imposed by the customer or the FMEA applicant actions to reduce criticality at or below requirement

4. Criticality evaluated by the FMEA team as too important (based on knowledge and experience) actions to reduce criticality

LINKAGES

• FMEA is not a stand-alone document• It is linked to

• the Product FMEA• the Process Flow Chart• the Control Plan

SUMMARY

An FMEA:– Identifies the ways in which a product or

process can fail– Estimates the risk associated with specific

causes– Prioritizes the actions that should be taken to

reduce risk– Is a living document