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Find all articles across all article series listed in reverse chronological order.
What are Variables Control Charts?
From NIST Engineering Statistics Handbook, section 6.3.2, with edits and additions.
During the 1920’s, Dr. Walter A. Shewhart proposed a general model for control charts as follows: [Read more…]
One of the first things taught in a data analysis class, or in first-grade math, is the plot. A graphical representation of the data. Bar charts, pie charts, histograms, box plots, and the x-y scatter plot. These and others simply help us to understand the nature of the data.
The ‘nature’? The data is only a record of an observation. Counts, colors, numbers, or something similar. The ‘nature’ is, to me, the behavior, maybe pattern, or story the data may reveal.
Consider a handy flow chart and set of descriptions that will assist you in selecting the appropriate control chart, or at least understand the differences. [Read more…]
The forums, chats, tweets (#bluelightofdeath), blogs, and mainstream media (CNN & Vancouver Sun) are looking closely at the launch of Sony’s Playstation. There are reports of dead on arrival and ‘blue light of death’ failures. One business blog discusses the need to understand and match customer expectations as a way to avoid bad press.
I find the expectation is pretty simple.
It should be simple
A brand new device, in this case, an expensive new game console, the entire experience of the purchase, transport, unpacking, hookup and first turn on should be a joy. The anticipation for those picking up the device on the first day comes crashing down to despair when the device fails to work. Products are expected to provide value, and you expect the device in front of you to work as expected. It’s simple.
I once explained to my son that not all units from production will work (he was in junior high school). He said he understood and that it is fine if the game console he buys just works. Ship the ones that don’t work to someone else. [Read more…]
Statistical process control (SPC) is not a control chart alone.
SPC is a set of tools and a thought process to identify, measure, monitor and improve important elements of product development and production. I’ve seen very good and very bad implementations of SPC. [Read more…]
Boeing representatives explained the Dreamliner would need an additional 6 months of work to bring the aircraft’s reliability on par with the existing 777 model.
They made the announcement at the start of the Dubai air show. Not a good start to a week of showing off the features of the aircraft. How does a companay respond to early reliability problems in the news?
Generally, even the most general reliability goal of a new product is to be as good or better than the last model. Sure, the Dreamliner has many new features, materials, and upgrades. Yet, it did as much or more design evaluation and testing as any model previously. [Read more…]
Before Norris-Landzberg’s study there was the work of Coffin and Mason.
One way to approach accelerated life testing is to use a model for the expected dominant failure mechanism. One such model is for solder joint low-cycle fatigue originally published by Coffin (1954) and Manson (1953), independently.
Norris and Landzberg proposed the plastic strain range is proportional to the thermal range of the cyclic loading (ΔT). They also modified the equation to account for effects of thermal cycling frequency (f) and the maximum temperature( T). They and other than empirically fit the parameters for the equation. [Read more…]
Recently I asked for recommendations for books for maintenance reliability engineers. The following list, in no order, are the recommendations. Thanks to all who participated. [Read more…]
A form of testing that reduces the time till results are known, ALT provides a means to estimate the failure rate over time of a product without resorting to normal use conditions and the associated duration.
For example, solar photovoltaic cells should operate for 25 years without failure. The product development time is less than a year for a new panel and the team wants to estimate the reliability of the cells over the 25-year duration. [Read more…]
At the start of class on reliability and maintenance engineering, one of the students asked,
“What is reliability engineering? What do you do?”
This made me think. What is it we do? How to you explain to someone our role?
I like to say, “We break things” with a big wink and a smile. And to some extent, as we explore what fails and how it fails. We most likely have to test our theories and break something. Or, when working with new product designs we employ tools to discover what will break. So, I suppose part of what we do is break things. Yet, that is not a complete answer. [Read more…]
When this posts I should be home from Nepal and mostly recovered. So, back to more details going forward. Take a look, work the problem, solve it, then show your work. Comment with why you chose your response and why you didn’t select one of the others. [Read more…]
The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man. In Maxims for Revolutionists (1903) by George Bernard Shaw
It is those that see the world as it should be that prompts change. I believe it is those resisting change to be unreasonable; I suppose it depends on your point of view. The idea or invention may be an inspiration or take diligent work, yet the real work is in changing the reasonable to a new way of viewing the world. Understanding everyone is not as unreasonable as yourself helps you prepare others for change. Challenging the resistance may label you as unreasonable. Be prepared and drive on, you are in good company. Fred Schenkelberg Reliability Quote of the Day, ISSN 2329-0099 http://www.fmsreliability.com/publishing/category/quotes/ where you can sign up for a daily quote sent to you via email —
I received a request from Quality Progress magazine to provide a quote and 100 words about the selection. The above is my submission. [Read more…]
When this posts I should be just getting home from Nepal (jet lag is no place to write posts). So, this post and the next couple are homework for you. Take a look, work the problem, solve it, then show your work. Comment with why you chose your response and why you didn’t select one of the others.
From question 19 of ASQ CRE 2009 sample exam. [Read more…]
Value for any business activity is a guiding principle to stay in business.
While not always about money, it is about value. We invest in product design and distribution, plant design and operation, to realize a benefit or return on the investment which makes the investment worth the effort and time. Same with our individual work- we endeavor to make a difference and realize not just a paycheck, (well some do). Increasing value is our responsibility as reliability professionals. [Read more…]
When this posts I should be near 17k ft altitude without electricity or internet – hoping for the best. So, this post and the next couple are homework for you. Take a look, work the problem, solve it, then show your work. Comment with why you choose your response and why you didn’t select one of the others.
Here is question 18 from the ASQ CRE 2009 sample exam. [Read more…]
