Your Reliability Engineering Professional Development Site
The process of creating a statement that includes the function(s), environment and use conditions, probability of survival, and duration for an item. It is the reliability performance objective for the item under consideration. It provides a detailed statement that is measurable to communicate the desired reliability performance of an item. Included is sufficient information to guide decisions related to material selection, design architecture, and types of or expected environmental and use stresses.
The following note and question appear in my email the other day. I had given the definition of reliability quite a bit of thought, yet have not really thought too much about a definition of ‘product life time’.
So after answering Najib’s question I thought it may make a good conversation starter here. Give it a quite read, and add how you would answer the questions Najib poses. [Read more…]
Reliability goals or objectives are just a starting point.
You goals represent your target at one point in time.
At best they represent what your customers expect for reliability performance at one point in time.
When goals are set well, they anticipate what your customer expects when they receive your product. In a perfect world, you customer will find the reliability performance just a bit better than expected.
It’s not a perfect world. [Read more…]
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. [Read more…]
“Keeping the end in mind”, “working toward a common objective” and “providing a vision” are all convention management wisdom based on setting goals.
Seeing a reliability goal is one of the first tasks when creating a reliability plan.
“How good (reliable) does it have to be?”
That is answered with a reliability goal statement.
There is a lot of uncertainty concerning a reliability goal. [Read more…]
Asking the right question is important.
During a review meeting (informal or formal) asking a few reliability questions may reveal weaknesses, strengths, or uncertainty. The design team has many priorities and reliability is often difficult to estimate, yet knowing what is and isn’t known provides a clear picture of risks for decision makers.
If you are a decision maker and need to ascertain the reliability risks of the current design, then asking a couple of questions may provide just the insights you need. It also conveys that reliability is on your mind and that you want to have answers that are meaningful and well thought out.
Selecting a supplier for components or subsystems involves many aspects including the desired reliability performance.
Once selected the ability of the supplier to provide items that meet or exceed the reliability requirements relies on their understanding of the requirements and operational conditions related to the specific item within the system. It also relies on the supplier’s knowledge of their own design and manufacturing processes as it related to the reliability performance. [Read more…]
The reliable performance of a system is important. It is important to the customer, to our business and to us.
Very few argue that we should ignore the reliability characteristics of a product. We also deem cost, time to market or feature set as important also. The trouble is we can measure the latter directly every day, where the reliability performance is often difficult to measure.
Coupled with probability is the duration over which the probability applies.
For example, if we desire 99 of 100 to survive, we must state over which period of time this applies. It is proper to state the couplet of 99% reliable over 1 year.
It is not sufficient to define reliability as ‘5-year product’ as it does not contain the information related to how many are expected to survive the 5 years. Likewise, it is not sufficient to say a product has 5 – 9’s reliability (meaning the probability of failure is less than 0.00001) as it does not contain the duration.
If the product has high reliability for only a few seconds, that does not help us make judgments about the first year of life. [Read more…]
Roll the dice.
It is about that simple if any one product will survive to a specific time. Every product has a chance, not a guarantee. The time to failure for each product is a function of the use, stresses, assembly, latent defects or imperfections, and many other variables.
The result is generally unknown. And, we often establish a reliability goal that includes the probability of success. Keep in mind that a probability is only meaningful when defined over a specific duration.
Once asked a customer what they wanted concerning product reliability.
She fully understood that some units will fail, that it’s matter of chance. She seemed understanding of the difficulty creating every product such that none would fail.
Then she confided that all that is fine, as long as the product she buys does not fail. [Read more…]
Reliability goals provide you and your team a focus for the reliability program. They provide a measurable way to design, test, and maintain systems that meet customer expectations.
A goal of any kind in a business is relatively easy to set and publish. They are not easy to entwine into the culture of the organization so the objectives desired by achieving the goal become a meaningful focus. A product development team may have hundreds of pages of specifications and a long list of priorities and objectives. Simple listing a reliability goal, no matter how clearly stated, may not be sufficient to garner the interest of your team.
Simple listing a reliability goal, no matter how clearly stated, may not be sufficient to garner the interest of your team.
Is it possible to foresee all reliability issues before a product launch?
No.
I don’t think so. Can we minimize surprises from field failures?
Yes.
The number of potential failures is often unknown.
Reliability engineering has value. It can improve product reliability, increase uptime, and drive customer satisfaction, for example.
Here are a couple of stories based on real situations that resulted in significant value for the organization.
It always seems there are more red lights when I’m running late.
This comment and others similar to it caught my attention lately. Is it just Murphy’s Law or something else?
There is an element of luck or chance in many events during our daily lives. The same is true when producing products and the resulting reliability. A lot has to go right for the product to work for the customer.
When something isn’t going as expected, we have a comparison that gains attention. If the lights are red more often, in theory, when I’m running late, maybe the lights are not turning red more often, it’s just that we notice.
For product development, it’s noticing the items that are going well and failing that matter. As reliability professionals, we need to continue to practice being aware of what is expected and what actually happens. [Read more…]
A life-support-equipment company manager desires to conduct a reliability program assessment. The company is experiencing about a 50% per year failure rate and at least the Director of Quality thought it should do better. One of the findings was related to reliability goal setting and how it was used within the organization.
Nearly everyone knew that the product had a 5,000-h Mean Time Before Failure (MTBF) reliability goal, but [Read more…]