Reliability Apportionment using Quality Function Deployment 2022-26-0017
It is important to allocate reliability goal of the system to its subsystems or components in the early design stage of the new product design and introduction project. Reliability allocation can be equal or weighted. For weighted reliability allocation the weighing factors are required for corresponding failure modes or subsystems or components. Currently, these weighing factors are determined using FMEA (Failure Mode and Effect Analysis) method, Engineering Judgement method or Expert Opinion method. An implementation of these methods takes longer time and efforts to converge the allocation output; because the input parameters to these tools are definitive of functional and physical domain of the system, which typically gets evolved, matured and finalized at the later stage of a product definition phase. Also, in certain cases deployment of these methods are prone to immature inputs causing rework and lack physics of failure analysis for life performance. These aspects of current methods make the implementation a lengthier and iterative process to converge reliability apportionment, which affects the development schedule, resource expenditure and time to market. In this paper, a comprehensive approach is proposed, which leverages QFD (Quality Functional Deployment) and FMECA (Failure Mode, Effects & Criticality Analysis). QFD enables transforming the functional/life critical VoC or requirements to CTQs, deriving physical-functional domain interactions and deriving rankings for various test items. FMECA enables criticality assessment for failure modes and defines weighing factors for predominant failure modes. This method works best for projects where we have iterative design process. It offers agile and efficient reliability apportionment that can be deployed in early phases of design, thereby accelerating design for reliability deployment.