Six sigma failure mode effects analysis

Chapter II: Six Sigma Define Phase

    Six sigma failure mode effects analysis

  • Process Performance

              Defects Per Unit (DPU) is universal measure of quality, used to calculate to get the average number of defect in given unit.

                                         DPU    =     Total number of Defect (D)


                                                                    Total units (U)

              Defects per million opportunities (DPMO) is an another measure of quality to calculate is the average number of defects per unit observed during an average production run divided by the number of opportunities to make a defect on the product under study during that run normalized to one million.

                         DPMO =     Number of Defects X 1,000,000


                                           Number of Defect Opportunities/Unit) x Number of Units

    Cost of poor Quality

              Cost of Quality chart creates the chart displaying prevention, appraisal and failure costs over time to demonstrate cost of poor quality.

    Cost of quality = Total cost acquired in maintaining standards quality levels + Cost of failure to maintain standard level.

    Cost of poor quality is divided into,

           1. Internal Failure cost: The costs spend on product or service, where it doesn’t meet the customer specification and delivered before the specific time leads into customer dissatisfaction and product erroneous. These includes,

                   •  Rework 

                   •  Stoppage 

                   •  Re-designing 

                   •  Shortages 

                   •  Failure analysis 

                   •  Re-testing 

                   •  Reduction 

                   •  Downtime 

                   •  Lack of supplenessand adaptability

    External Failure cost: The costs spend on product or services lead to dissatisfaction during post-delivery. These includes,

                   •  Grievances 

                   •  Patching up goods and redo services 

                   •  Warranties 

                   •  Customers’ bad will 

                   •  Sales reductions causes heavy loss 

                   •  Costs of environment.


              Failure method is a method mismatch with customer expectation; Effect Analysis Method is procedure to identify the failure of a product /service within a company or outside customer. In six sigma green belt method, FMEA is tool to arrange alternate activities when a system gets failure.

              Failure Mode Effect Analysis Method is used to estimate and calculate risk of product or process, FMEA is a tool to reduce life cycle assurance costs. FEMA is a preventive measure to eliminate faulty process. Cost allocated for FMEA is monotonous, but implementation process of FMEA and ideas generated from cross-functional team would result in success. By calculating RPN helps to define action plan to eliminate failure in a system

              Risk Priority Number RPN= (S*P*D) Severity, Probability, and Detectability.

    How to calculate Risk Priority Number (Model Calculation)

              Severity shows the serious effect leads to potential risk in a process.

    Severity Standards for FMEA:

    1 Irrelevant

    4 Slight

    9 Important

    16 Critical

    25 Disastrous

    Probability occurrence relates with potential risk occur in a system. 

    Probability Standards for FMEA:

    1 Occurrence of unlikely probability 

    3 Occurrence of remote probability 

    5 Occurrence of occasional probability 

    7 Occurrence of moderate probability 

    9 Occurrence of High probability

    Detectability is the probability of failure identified prior to impact of failure in a system.

    Detectability Standards for FMEA: 

    1      High degree of detectability

    3 Good detectability

    5 Likely to detectability

    7 Fair detectability

    9 Low or detectability

    Risk Score Matrix







    Business Impact






    Likelihood standards

    Almost certain





    Classification of Risks

                        1.  High Probability and High Impact:Risks are show-stoppers and priority of any mitigation plan.

                        2.  High Probability and Low Impact:Standard risk,mitigation plans are used since high frequency but theimpact is low manageable.

                        3.  Low Probability and High Impact:The value would be zero.They have huge impact on operations.This stage is called as "Black Swans"

                        4.  Low Probability and Low Impact: Risk is insignificant. The damage occurred in this pattern would be minimum.This patterndoesn’t focus on mitigation plans.


              Design Failure Mode Effect Analysis (DFMEA) is an application for product design, provided at the initial stage of product design. DFMEA is procedure used in engineering to fine the chance of failure in a system. It is a complete manual provides key functions in design and defines potential causes of failure modes.After identifying the failure modes, series of process takes place to reduce the cause of failure through implementation.

              This document contain product data, different phases data pass through, team handling the project and revised data. DFMEA Matrix is tool to states data or information to team. DFMEA Matrix consist, X axis represents severity and Y axis represents occurrence Cells in the matrix contain detectability.

    How to calculate the DFMEA:

                        1. Calculate Risk Priority Number.

                        2. Define corrective and preventive Action.

                        3. Ranking Action Based on the RPN


              Process Failure Mode Effect Analysis (PFMEA) is used for analyzing failure mode for specified process occurs in an organization. PFMEA used to define the cause of failure and failure mode and eliminate failure in process. PFMEA is atypical tool used across every organization to evaluate possible failure and identify the failure modes by gathering information.

    How to calculate the PFMEA: 

                        1. Calculate Risk Priority Number

                        2. Describe corrective and preventive Action

                        3. Ranking Action Based on the RPN

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