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…]
Archives for November 2013
“Thanks for taking time to do these sessions. Extremely helpful.” – Keron
It Should Just Work
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 Overview
Basic introduction to key concepts of SPC
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…]
Early Reliability Problems in the News
Working down product launch reliability problems
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…]
Norris-Landzberg Solder Joint Fatigue
Before Norris-Landzberg’s study there was the work of Coffin and Mason.
Coffin-Manson
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-Landzberg
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…]
Recommended Books for Maintenance Reliability Engineers
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…]
Accelerated Life Testing
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…]
What is Reliability Engineering?
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?
Quick Answer
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…]
Two question challenge
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…]