The best time is at the product conception. The second best time as early as possible in the product development process.
It may change. Be refined. Altered later.
That is fine, yet the initial concept needs the boundary condition of a reliability goal.
I would argue that the initial napkin sketch of a new product is the right time to establish the reliability goal.
The initial thoughts may include a rough idea of the duration of use.
Is it a one time use, maybe with long time storage requirements. Or it is a 24/7 use model providing continuous functionality? These concepts certainly influence the product architecture and design.
Function, environment, duration are elements of a reliability goal. The missing element is the probability of success, or how many should survive the duration. Add that to round out the reliability goal as early as possible.
The design process and reliability
Henry Petroski in Design Paradigms suggests designer naturally design away from failures.
They have the intent to create a product that works and works over time as expected.
The design process for a new product often starts with a potential solution for a problem or need. The product concept is the seed of an idea that may solve the problem. This concept will evolve, not necessarily linearly, nor always successfully, to a final product.
The customer will be the final judge of the product’s ability to solve the problem or meet a need. One criterion is product reliability. The customer with one product will eventually judge if the product meets their reliability performance expectation. Did the product work long enough without failure?
The reliability goal is our estimate of the customer’s expectation.
Thinking about the reliability requirement early in the development of a product informs the decisions concerning the evolution of the product.
Establish reliability goals early and refine along the way
Reliability performance is important. It is thought about early in the design process.
As soon as you write down any requirements or specifications that should trigger writing down the reliability goal. Like any of the specifications, the reliability specifications can change.
When documented well, the reliability goal provides essential information for anyone designing or producing the product. I would argue that have a clear reliability goal at product inception is the most valuable.
What is your experience? Do you set reliability goals and if so when in the lifecycle? Leave a comment below and join the conversation.
3 Elements of Reliability Goal Setting (article)
Guiding Programs by Product Goals (article)