on Product Reliability

The Vasa is a Swedish ship that was constructed between 1626 and 1628.  It is a great story of an engineering disaster,  well that’s how it is labeled. It doesn’t take too much investigation to see it is really a leadership disaster.

I saw the Vasa in beautifully restored condition at it’s museum in Stockholm Sweden.  It was retrieved from the ocean floor in 1961.   Amazingly after almost 300 years it was intact and well preserved in the freezing waters off Sweden.  This is it’s story… and warning! [Read more…]

The importance of reliability education in a product development program cannot be understated.  A design initiative with mechanical content can be created solely by the mechanical team, same for electrical, and software.  These other disciplines will create a better product if they collaborate from the start, but this is not necessary. A successful product can still be created if they intersect later.  Reliability doesn’t have this flexibility.  Reliability tools don’t have a deliverable like a function or a feature.  They are an assist for the function or feature during the process of creation.  As an assist discipline, it only works if implemented while the other processes are in motion.  Attempting to add it after the design has been completed requires a deconstruction of the previous work if improvements are needed. [Read more…]

I just returned from the IEEE ASQ Accelerated Stress Test and Reliability Conference, held this year in Austin, Texas.  It’s always been a great conference. There is such a good comradery and sharing of knowledge when a large group comes together on such a specific topic. I meet a lot of great people from many different industries, all with great experience to share. [Read more…]

Confidence is used in reliability to give a probabilistic value to the likelihood that a taken measurement will represent a full population.  It is determined by measuring a sample size and then using a selected statistical distribution table to translate to a likelihood. Emotional confidence is how one feels about making a decision based on known information at a specific point in time.   Similar but different. But it is important to connect them.  This is why. [Read more…]

I like the occasional good catchphrase.  I typically tend to speak in analogies and anecdotes and many of my customers and colleagues have suggested documenting them.  So on occasion, I will write them in my notebook.  Here are a few. [Read more…]

One of the most difficult challenges of incorporating reliability activities with program planning is estimating the time it will take to demonstrate reliability.  Demonstrated product reliability is typically measured as a confidence in a product’s capability to achieve a reliability goal. At product release, the business unit may feel comfortable with their target market and warranty goals with a demonstration of a 90% confidence in the products reliability goal of 99.1%. [Read more…]

Here is a common situation that is considered when reliability testing is being planned. Let’s use letters to designate depth in a product component structure. The top level product is level “A” and a component in top sub assembly is “B”. A sub assembly, of a sub assembly, of a sub assembly, is at level “D”.  So is it more efficient to test the component at level “E” or at level “B”?

Question: Is it more efficient to test the component at level “E” or at level “B” to demonstrate it’s individual goal? [Read more…]

Weibull analysis is a tool that is used for characterizing the behavior of a data set.  The value of characterizing a data set is being able to make predictions of failure rate for the same or a similar population. Input to the Weibull analysis is time to fail for all failed units and running time for operating units. The assumptions for the data set are critical to ensuring the right information is included in the analysis.  This may include root cause analysis of the failures so they can be characterized as wear-out or use stress related. It would be beneficial to separate these two data sets because their characterization and behavior will be quite different Weibull factors. [Read more…]

If you had to section the history of reliability into only two periods I believe the dividing point would be around 1950.  The first section, stone age to 1950, the “Robust” era; 1950 to today, the “Margin” era.   In the robust, era reliability concerns were addressed by creating a design that was orders of magnitude stronger than required, “over-engineered”.  This protected against the variability of fabrication, use, and environment.  If it was made sloppily with low tolerances, it still worked;  Used for an unintended purpose, still worked; Left out in the snow, dropped in the river, run over by a horse, buried in the sand; still worked. [Read more…]