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Reliability Notes

Design for reliability (DfR) is inherently an integral aspect of the design and development
1. Activities in the concept phase
a. Defining user needs in terms of reliability, operating conditions, and stresses
b. Gathering voice of customer and defining the business case in terms of maximum
service cost up front
2. Activities in the design phase
a. Creating reliability models, identifying critical components
b. Allocating reliability to components based on user needs, duty cycle, and operating
conditions; defining reliability thresholds for subsystems
c. Conducting reliability analysis and feasibility, defining top failures in failure mode
and effects analysis (FMEA)
d. Defining technical specifications for parts per reliability allocation and requirements,
and selecting reliable parts
3. Activities in the verification phase
a. Developing and following a reliability growth plan
b. Simulating realistic usage stress level in testing, and properly testing for reliability
c. Reviewing supplier reliability
4. Activities in the design transfer and production phase
a. Monitoring and tracking reliability by setting failure thresholds on components and
b. Setting proper screening stresses in manufacturing processes and testing
c. Proactively updating the service model
Quality, Reliability, and Robustness
There is often confusion on the differences between the reliability, robustness,
and quality of a product.
Reliability as the probability that a product will perform its intended function for
a specified time under specified conditions.
Robustness is often defined as insensitivity to variation of the ability of a system
or product to perform its intended functions dependably in the presence of noise
The definition of quality is a bit more elusive.
To conform to requirements.
Fitness of purpose