Your Reliability Engineering Professional Development Site
What happens when a product you produce fails? You customer may call and return the product. They may expect you to provide a replacement or refund.
Does it matter if the failure was due to a capacitor or motor that you didn’t design, just purchased?
No.
Does it matter if a supplier’s supplier made an error that directly lead to the failure?
No.
You customer experienced a failure and since the purchase was from you, you are expected to make it right.
To help you with taking standardized exams such as ASQ Certification exams, here are some tips that I learned a long time ago that have helped me. There may be cultural differences between the USA and other countries that would invalidate some of these. If anything that I included goes against what the specific examination authority recommends for test taking rules or strategy, go with their recommendations.
There may be cultural differences between the USA and other countries that would invalidate some of these. If anything that I included goes against what the specific examination authority recommends for test taking rules or strategy, go with their recommendations. [Read more…]
The WordPress.com stats helper monkeys prepared a 2014 annual report for this blog. Thanks to everyone for making this blog and program a success.
Here’s an excerpt:
The concert hall at the Sydney Opera House holds 2,700 people. This blog was viewed about 26,000 times in 2014. If it were a concert at Sydney Opera House, it would take about 10 sold-out performances for that many people to see it.
There are two basic philosophies when creating a reliability plan for a new product or system.
One is to experiment with prototypes as quickly and often as possible, the build, test, fix, approach. Or, you can research and model detailed aspects of the materials and structures to characterize the strength of a product or system, the analytical approach.
Both methods have obvious applications and not so obvious limitations. [Read more…]
Products that fail may create an unsafe situation.
For catastrophic failure mechanisms, the design team may consider establishing a safety factor or margin of safety policy. This provides the design team guidance as they size structures, select components, and evaluate performance and reliability.
A safety factor or margin are measures of the separation of the stress and strength for a specific failure mechanism. If something has a 2x safety factor it implies the element is twice as strong as the expected stress. [Read more…]
The short answer is, everything varies.
The longer answer involves the agreement between what is possible and what is desired.
If we could design a product and it could be replicated exactly, including every element of the product, we would not need tolerances. Any part would work with any assembly. We would simply specify the dimensions required. [Read more…]
Worst case tolerance analysis is the starting point when creating a tolerance specification. It is a conservative approach as it only considers the maximum or minimum values of part variation, whichever leads to the worst situation.
The worst case method simply adds the dimensions using the extreme values for those dimensions. Thus if a part is specified at 25mm +/- 0.1mm than use either 25.1mm or 24.9mm, whichever leads to the most unfavorable situation. [Read more…]
The short answer is, everything varies.
The longer answer involves the agreement between what is possible and what is desired.
If we could design a product and it could be replicated exactly, including every element of the product, we would not need tolerances. Any part would work with any assembly. We would simply specify the dimensions required.
Instead, variation happens.
Widths, lengths, weights, roughness, hardness, and any measure you deem worth specifying will vary from one part to the next. Manufacturing processes impart some amount of variation between each item produced. In many cases, the variation is acceptable for the intended function. In some cases, the vacation is unacceptably large and leads to failures. When the design does not account for the variation holes will not align, components will not fit, or performance will be poor.
The better reliability performing systems start the design process with controlling variability.
Variability of materials and processes involved thought the product lifecycle. Reliability performance occurs as a result of the decisions made throughout the design process.
When focused on understanding and minimizing variability, the design becomes robust and reliable.
In the past, a reliability engineer developed their skills over years of practice under a mentor.
Today, a reliability engineer is a jack of all trades and needs to be a master of them as well. Reliability has developed into its own science and is a discipline in its own right which crosses many fields of engineering, statistics, and physics. One way to show you have the broad understanding needed to succeed in the diverse field of reliability is the Certified Reliability Engineering (CRE) from the American Society of Quality (ASQ). [Read more…]
It’s Friday afternoon and the phone rings. It is another customer complaining about your product not working. This is the fifth call this afternoon. Something is wrong and you’re responsible for making it right.
The natural failure analysis process starts across your team. Gather information, determine the scope of the issue, work to understand the root causes, and implement an appropriate solution. This may involve stopping production, halting shipments, or even a product recall.
Initially, you just have more irate customer calls than a typical Friday afternoon. [Read more…]
One method to define an organization’s approach to reliability is to create a reliability manual. Many organizations already have a quality manual as required for ISO 9000 or similar certification. Reliability may be a section of the larger quality manual or simply integrated into the same document. [Read more…]
The ASQ CRE exam is difficult. The individual elements of the body of knowledge are not in themselves difficult, it is just such a broad range of topics that mastering all the subjects is a challenge.
The CRE Body of Knowledge includes elements of leadership & management, testing & failure analysis, and basic & advanced & reliability statistics. Reliability engineers work across the spectrum of consumer product design to plant maintenance.
Depending on your experience you may have a wealth of experience with availability modeling and repairable system data analysis, and have little experience with design for reliability practices. [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.
Common mode or common cause failures related to redundant systems where one cause can lead to the failure of otherwise redundant elements leading to system failure.
Elements which should fail independently are under some circumstances dependent.
When considering the probability of individual paths in a complex redundant system, take due care to consider the common mode failures which may have a higher probability than any single path in the system. [Read more…]