Your Reliability Engineering Professional Development Site
Quality during Design is the place for product designers to use quality thinking throughout the design process to create products others love, for less.
It costs our customers to own our designed products. It costs them initially to purchase it, but it also costs them to use it, maintain it, repair it, and eventually dispose of it. And it costs our company in ways too, like processing, training requirements for customers, and warranty repair costs.
Life cycle costing can help our team choose between design alternatives, like alternate design options, features, manufacturing methods, or suppliers.
Good reliability requirements are going to drive our design decisions relating to the concept, the components, the materials, and other stuff. So, the moment to start defining reliability requirements is early in the design process. But, what makes a well-defined reliability requirement? There are five aspects it should cover: do you know what they are?
We’ll describe what makes a good reliability requirement and examples of common (but not good) requirements.
We have good requirements for the reliability of our design. We also have a preliminary design with ideas of how we’re going to manufacture it. Is our design idea good enough? Are there things we should do to improve its performance and reliability?
For a physical product, there are three general stages in its life cycle. In many cases the failure rates of physical products can be represented by a reliability bathtub curve. This curve is really a plot of a hazard rate function, also known as a failure rate function. We talk about data collection in the early design phase, what types of failures are typical for each phase, and design decisions we may make to improve our reliability, based on the failure rate function we plot for our system.
Flowcharting isn’t just useful for manufacturing processes. We can use them in lots of ways to help us with design of products and to identify quality characteristics. After all, products are used by people, and the way in which they use them is a process.
We also talk about specific flowchart analyses and how they can be used to analyze the user process for design.
Defining tolerances for our quality characteristics is sometimes not an easy task. If we set tight tolerances, it could be costly to make with a lot of rejects and rework in the future. If we’re too sloppy with our tolerances, then it can affect the functionality of our product, leading to unhappy customers, and also possible rework and scrap. There’s economics involved in setting-up tolerances.
Genichi Taguchi related his measure of quality (variation from the target spec) with economics, called the Taguchi Loss Function. It’s used to calculate the cost (in money) of a certain deviation from a target value. It assumes that the farther our quality characteristic is from our target value, the more costly it is to us.
We talk about how we can use the Taguchi Loss Functions as a way for us to set tolerances for our designs. Scroll lower to get an interactive tool and the equations.
When we’ve identified a risk to our design or user process – and that risk can pose a potential harm – how many controls do we need to add?
We discuss prevention vs. detection controls, ALARP, as low as possible, and some scenarios where we could (and maybe couldn’t) justify a risk as acceptable without adding additional controls.
How we describe and approach the issues we need to solve can affect how we react to them. We know we’re supposed to be solving for root causes. But are we, instead, really just addressing symptoms? Are we celebrating the quick fix and then moving on without addressing the root of our issue?
“If you define the problem correctly, you almost have the solution.” – Steve Jobs
Recognize the common mishaps of us solving symptoms instead of really getting to the causes. And, clearly describe our problem in two parts (statement and description of facts) to be confident that we’re moving toward solving the causes.
Objectives are goalposts of what it is we’re trying to accomplish. Though they’re only a part of planning a project, if we don’t have well-defined and clear objectives, it could lead to us not having the stellar project results we want. Our objective should be a SMART ACORN. We review these two, complementing acronyms as ways to check that we’re setting up our project for success.
Standards are everywhere, and lots of organizations are sourcing and creating them. The U.S. Federal Trade Commission held a workshop 2019 that recently made the news, again, in July 2021. It was called “Nixing the Fix: a Workshop on Repair Restrictions”. Here’s what it’s about: manufacturers are not creating products with standard parts, or their design is created so its difficult for consumers to repair.
Are standards part of the answer? How can we proactively use them for design? Why should we?
Before we can link customer needs to design, production, and service of our products, we need to listen to and understand the voice of the customer. We review 6 common VOC collection strategies, and talk about their pros and cons. We also discuss an affinity diagram process, which may help our team organize all of the data to get to customer needs.
We can look at test methods like a product in and of itself. Because tests also have requirements and need to produce usable results, we validate against those requirements. Validating our test method also ensures that they are precise and accurate.
We talk about things to consider when looking at product tests: tying test methods to the product’s use environment, standards, and cumulative effects of testing.
Creating specs for suppliers and producers is generally at the forefront of our thoughts about the activity. But, it’s also important to design for our QA friends, too, for inspection.
We talk about what acceptance sampling is all about. We also step through a thought process for identifying and creating design features for inspection using FMEA.
When designs fail we can take on damaging mindsets while we’re deciding our next steps, and this can lead us to bad decisions. We explore this and give some examples of pitfalls. We also talk about what to do within the design-realm to prepare for and combat those mindsets. Finally, I share my mantra when designing activities get tough with failures.
In the quality world, kaizen is a tool for continuous improvement under the umbrella of a Lean philosophy. The quality-tool kaizen is just one layer of a larger, overarching idea that we benefit from small, incremental improvements made consistently.
Kaizen as a tool involves all employees of the company toward continuous improvement. The way kaizen events are done helps to promote the continuous improvement philosophy throughout the business through its effect on culture, time, proof, and teamwork. We talk more about how this all fits together in the podcast.
A Fishbone Diagram is named for its looks because it resembles the bones of a fish drawn on paper. Its less creative names are Cause-and-Effect Diagram and Ishikawa Diagram. It’s popularly known to help with root cause analysis. But, we can also use it to help with goals and to evaluate a potential solution.
Why is it a Supertool? Just creating its headings helps us to better define our question. Writing it out as a graphical organizer helps organize jumbled thoughts. And, when paired with a 5W2H approach and the 5-whys, it can help us dig to the root causes.
I’ve included some abbreviated examples of fishbone diagrams; click the thumbnail for a larger version (notice that my root causes follow the 5-whys). And, listen to the podcast (or read the transcript) to learn more about Fishbones and their construction and uses.
