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Prep notes for ASQ Certified Reliability Engineer exam ISSN 2165-8633
The CRE Preparation Notes series provides you with short practical tutorials on all the elements that make up the ASQ CRE body of knowledge. The articles provide introductory material, basics, how-tos, examples, and practical use guidance for the full range of reliability engineering concepts, terms, tools, and practices.
Keep your knowledge fresh by regularly reviewing topics and tools that make up reliability engineering.
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You will find the most recent tutorials in reverse chronological order below.
One of the simplest ways to learn design of experiments, DOE, is to just give it a try.
The Taguchi DOE approach uses orthogonal arrays. This subset of the possible approaches to DOE simplifies the process to create and analyze experiments.
Let’s plan a simple experiment using the Taguchi DOE approach. [Read more…]
When we understand how something fails, we can create a mathematical model of the effect of stress or load on the time to failure behavior.
The model may take different forms, yet it is the ability to related the conditions surrounding the use of a device to its eventual demise that is essential. The specifics include a molecular level of detail in some cases.
Physics of Failure models focus on the particular relationships between stresses and materials. [Read more…]
As with strength-strength analysis, derating is a means to design robust systems.
Derating is an intentional process applied to every component of a product to reduce the opportunity of a component witnessing more stress than it is capable of withstanding.
The additional robustness also reduces the amount of damage the stress may impart, thus prolonging the life of the component. [Read more…]
The ASQ CRE Exam is daunting.
While you may desire to become certified, you also know the CRE body of knowledge is broad. The exam is 150 questions in four hours that may tax your ability to achieve a passing score.
There is a lot to know in reliability engineering. Your journey of learning really never ends. [Read more…]
The definition of reliability includes four elements.
One of them is the intended environment where the device or system will experience a range of stresses.
The knowledge of where and how an item will operate enables:
Beyond the part reliability specification, you may also add conditions or requests to your reliability specification for your supplier.
The communication with your supplier should include sufficient information that they fully understand your reliability performance expectations. When buying or contracting with a supplier, you are the customer.
Be clear about your reliability requirements including constraints and conditions. [Read more…]
Unless you are working with raw materials directly, you rely on your suppliers to provide reliable parts.
Do you suppliers know your reliability objectives for the parts they supply?
If you didn’t tell them, they probably do not know. If you did tell them, did you make it the reliability specification clear and understandable?
As with any specification, clear communication is essential. Guessing or assuming both parties know and have the same reliability goals is, well, not a good practice. The ability of a supplier to build and deliver the parts that meet all your specification has to include a clear and understandable reliability specification.
There is a range of common reliability specifications in use, some are better than others. Let’s start with a brief review of reliability specification types.
Then briefly outline how you establish the reliability specifications for each supplied component. [Read more…]
Even products with relatively quick design cycles and short stays in the market deal with part obsolescence.
Long design periods along with long durations in service or in production simply increases the chance that one or more parts will become obsolete.
Designing systems with part obsolescence in mind helps. Working with suppliers to select parts with many sources, with long-term plans to produce, and with long term commitments, all may help. Even then, companies change priorities, go out of business, or simply discontinue the part you need. [Read more…]
One aspect of creating a new product or system is the sourcing of parts, components, and materials.
Gone are the days of your organization providing every element of the final product. Henry Ford’s supply chain for early Ford automobiles includes their own forests, rubber plantations, and iron ore mines. [Gelderman, 1981]
We increasingly rely on the supply chain to create the necessary parts for the design’s functionality. Then to continue to supply those same parts for decades, in some cases. [Read more…]
Software elements of a product or system take time to create. Thus re-using blocks of code developed for previous applications may save on development time. [Read more…]
A fault tree analysis (FTA) is a logical, graphical diagram that starts with an unwanted, undesirable, or anomalous state of a system.
The diagram then lays out the many possible faults and combination of faults within the subsystems, components, assemblies, software, and parts comprising the system which may lead to the top level unwanted fault condition. [Read more…]
Physical products are made up of materials.
The materials including metals, polymers, adhesives, and many others experience loads and stresses during assembly, transport, storage, and use.
Selecting the right materials such that they both meet the needs of the customer and are sufficiently reliable relies on understanding how the material will respond to the applied stresses over time.
As with parts selection, one way to determine if a material is suitable for your application and end use is to monitor the material’s performance over time in your products. The trouble is it also transfers the risk of failure (the unknown risk of failure) to the customer.
In many cases this is unacceptable. [Read more…]
A product or system may fail for many different reasons.
One cause is a faulty part. A component is susceptible to failure when either improperly used in the design or is a damaged or flawed component. [Read more…]
When products were crafted one at a time, the design and manufacturing process was often done by the same person. The craftsman would design and build a chest of drawers or carriage.
Some trades would employ apprentices to learn the craft, which included design. Larger projects may include an architect or lead designer along with a team of engineers.
Yet the shop or site for the railroad engineer or bridge was not far allowing close communication between the ironsmith and design team. [Read more…]
I’ve often said, “reliability occurs at the point of decision.”
At the point of design during the design process. At each and every decision.
The design team of engineers establishes the bulk of the reliability capability early in the design process. The team’s decisions about materials or shape, concerning inventions or outsourcing, about how and where to build the product, and many more decisions impact the final product’s reliability performance.
Reliability is designed into the product right from the start. [Read more…]
