on Tools & Techniques

A listing in reverse chronological order of articles by:

Dennis Craggs — Big Data Analytics series

Perry Parendo — Experimental Design for NPD series

Dev Raheja — Innovative Thinking in Reliability and Durability series

Oleg Ivanov — Inside and Beyond HALT series

Carl Carlson — Inside FMEA series

Steven Wachs — Integral Concepts series

Shane Turcott — Learning from Failures series

Larry George — Progress in Field Reliability? series

Gabor Szabo — R for Engineering series

Matthew Reid — Reliability Engineering Using Python series

Kevin Stewart — Reliability Relfections series

Anne Meixner — Testing 1 2 3 series

Ray Harkins — The Manufacturing Academy series

by Dennis Craggs Leave a Comment

A Primer on Probability Plots

In my prior article, “A Primer on Probability Distributions”, the usage of different types of histograms to display data was discussed. The histogram would acquire a bell shape if the data were normally distributed. The main limitation of the histogram approach is that the shape of the histogram can change radically with the selection of the bins used. Instead, a probability plot could be used.

This article discussed probability plots. They are extremely useful for the analysis of big and small data sets.

[Read more…]

by Carl S. Carlson Leave a Comment

Understanding FMEA Effects: Part 2

Problems and Solutions

Can you identify the effect of the door latch-pin failure in this case study? The loss of the aft cargo door on the American Airlines DC-10 aircraft will be the focus of this Problems and Solutions article. This real-life case study is being used to practice identifying FMEA elements.

[Read more…]

by Carl S. Carlson Leave a Comment

Understanding FMEA Effects: Part 1

If a Tree Falls in a Forest . . .

Why do you think FMEA procedure requires effects to be taken to the system or end user? Why not describe the consequence only at the local level. If a bolt in a complex system fails, the parts that the bolt was clamping together may come apart. Isn’t that enough?

“Wisdom consists of the anticipation of consequences.”
Norman Cousins

[Read more…]

by Dennis Craggs 3 Comments

Estimating the Normal Distribution Parameters and Tolerance Limits

Frequently, data collection is the most time consuming and expensive part of a project. Consequently, people work with small sample data. There is too little data to plot a histogram, so the analysis assumes the underlying population is normally distributed.

A frequent error is to assume the sample average and standard deviation are the population normal mean and standard deviation. When small sample sizes are being analyzed, these assumptions lead to estimation errors.

Methods to make better estimates are discussed in this article. [Read more…]

by Carl S. Carlson Leave a Comment

FMEA Q and A – Managing System Changes

FMEA Q and A

In this Q and A article, a reader asks an interesting question about whether or not to update a System FMEA, when making subsequent changes to lower-level items. This is an excellent question, and shows the reader has good insight into the application of FMEA.

“Judge a man by his questions, not his answers.”
Voltaire

[Read more…]

by Carl S. Carlson 7 Comments

Understanding FMEA Failure Modes: Part 2

Problems and Solutions

Whether you are new to FMEA or more experienced, these problems will challenge your skills. The intermediate/advanced problem uses an actual airline disaster to challenge readers with an FMEA problem, and practice identifying the elements of an FMEA.

[Read more…]

by Dennis Craggs Leave a Comment

A Primer on Probability Distributions

The most common types of engineering data are measurements. There can be a few, thousands, or millions of data points to analyze. Without analytic tools, one can get lost in the data.

This article presents

Dotplots
Data if frequently clustered about a central value and displays variation.
Frequency histograms
Distribution characteristics
Normal Distributions

[Read more…]

by Perry Parendo Leave a Comment

Prototypes and Learning

Prototypes Help You Learn About Your Product

To reduce schedules, prototype cycles are often randomly slashed. Eventually the time and resources are needed and create cost and schedule over runs. We need to recognize that prototypes exist to help us learn about our product. If we use a risk based test strategy approach, we can test at lower levels to gain the required understanding. Then, we can confirm our learning with the higher level, system prototypes.

Just 4 minutes and 19 second long. To me, a prototype does include bench testing at lower levels as long as it includes the relevant functionality to represent the area for learning. [Read more…]

by Carl S. Carlson 2 Comments

Understanding FMEA Failure Modes – Part 1

Why Describing the Mode of Failure is Essential

Do you know why we ask for the “mode” of failure when performing FMEAs? This article will provide theory and practical examples of defining failure modes, and highlight an application tip that can improve your FMEA effectiveness.

“I haven’t failed, I’ve just found ten thousand ways that don’t work”
Thomas Edison

[Read more…]

by Anne Meixner 1 Comment

The Test Attributes of Controllability and Observability

If a tree falls in a forest with no one around to hear it, does it still make a sound?

If a fault occurs in a combinational circuit but its masked at the outputs is it still a fault?

If you can’t excite a fault from the circuit inputs does it really exist?

If you can’t propagate a fault to an output pin, does it matter?

In assessing an integrated circuit’s testability engineers consider the concepts of controllability and observability. In these specific characteristics of testability came up often the academic test literature of the 1970’s and 1980’s. The challenge back then was automatic test generation and fault simulation. [Read more…]

by Perry Parendo Leave a Comment

Model Building

Statistical Model Building

Model Building is a key theme for several advanced techniques. It boils down to creating an equation. Done well, one can predict and forecast how things will behave. Creating understanding reduces product risk and increases the chances for success.

Just 3 minutes and 9 second long, lets get the basics of model building to improve your understanding of how a system works. [Read more…]

by Carl S. Carlson 7 Comments

FMEA Q and A – System-Level Functions

FMEA Q and A

In this question, a reader asks how to define system-level functions, and how they are different from subsystem and component functions.

“A prudent question is one-half of wisdom.”
Francis Bacon

[Read more…]

by Perry Parendo 6 Comments

ANOVA Calculation Example

An Explanation and an ANOVA Calculation Example

Our white paper regarding t-test calculations has been very popular. Those that use the t-test tool regularly have commented “I finally understand what it is all about.”

The natural question they ask me next is “have you done anything with the F-test?” It is another common tool and one that is equally misunderstood.

Due to popular request, here is our attempt at explaining the F-test tool, in the two possible methods of use. [Read more…]

by Carl S. Carlson Leave a Comment

Understanding Functions – Part 2

Problems and Solutions

Do you consider yourself an FMEA beginner or are you more experienced? Challenge yourself with these problems about FMEA functions, and see how you do. One of the best ways to learn is by pondering application problems and seeing of you can solve them.

If you haven’t yet read last week’s article Understanding FMEA Functions – Part 1, it would be a good idea to read it now, as the questions are based on that article.

[Read more…]

by Anne Meixner Leave a Comment