on Product Reliability

A listing in reverse chronological order of articles by:

Kirk Grey — Accelerated Reliability series

Les Warrington — Achieving the Benefits of Reliability series

Adam Bahret — Apex Ridge series

Michael Pfeifer — Metals Engineering and Product Reliability series

Fred Schenkelberg — Musings on Reliability and Maintenance series

Arthur Hart — Reliability Engineering Insights series

Chris Jackson — Reliability in Emerging Technology series

by Fred Schenkelberg Leave a Comment

Is this FMEA good?

It is rare that a third party generated FMEA/FMECA has any value. The development or manufacturing teams and supporting staff should comprise the bulk of the study’s team. Team size for a specific study would include 4 to 10 individuals.

The FMEA/FMECA should provide clear action items that may include:

Conduct research or experiments to understand and quantify uncertainty. This may include exploring how an item responds to specific stress, errors or inputs. Or include experiments to estimate the occurrence rating for a specific potential cause of a failure mode. [Read more…]

by Fred Schenkelberg 1 Comment

Uncovering Hidden Field Failure Problems

A reliable product does not fail often. Customers expect to a level of reliability performance and failures that occur too early dash their expectation.

The design and development team work to create a robust product. To meet the customer’s reliability expectations. The team may use a range of tools to detect any reliability problem prior to launch.

Yet, customers do uncover problems that surprise us. This may be a problem with how we identify and resolve risks, yet it could also be the development process didn’t look close enough to find the issues. Or, worse, we saw the issue and ignored it. [Read more…]

by Fred Schenkelberg 1 Comment

5 Steps to Create a Reliability Plan

A specific reliability plan may include any number of specific tasks. To build an effective plan you need the knowledge of the individual tools and techniques, plus how they may fit together to create an overall plan to achieve your goals.

Reliability Goals

Of course, this starts with establishing complete reliability goals that include function, environment characterization, probability of success (reliability) and duration.

I recommend setting specific goals for setup/installation (early life), the warranty period and the expected customer use period. [Read more…]

by Fred Schenkelberg Leave a Comment

Purpose of a Reliability Program

The reliable performance of a system is important. It is important to the customer, to our business and to us.

Very few argue that we should ignore the reliability characteristics of a product. We also deem cost, time to market or feature set as important also. The trouble is we can measure the latter directly every day, where the reliability performance is often difficult to measure.

[Read more…]

by Fred Schenkelberg Leave a Comment

Duration and Reliability Goals

Coupled with probability is the duration over which the probability applies.

For example, if we desire 99 of 100 to survive, we must state over which period of time this applies. It is proper to state the couplet of 99% reliable over 1 year.

It is not sufficient to define reliability as ‘5-year product’ as it does not contain the information related to how many are expected to survive the 5 years. Likewise, it is not sufficient to say a product has 5 – 9’s reliability (meaning the probability of failure is less than 0.00001) as it does not contain the duration.

If the product has high reliability for only a few seconds, that does not help us make judgments about the first year of life. [Read more…]

by Fred Schenkelberg 2 Comments

Probability and Reliability Goals

Roll the dice.

It is about that simple if any one product will survive to a specific time. Every product has a chance, not a guarantee. The time to failure for each product is a function of the use, stresses, assembly, latent defects or imperfections, and many other variables.

The result is generally unknown. And, we often establish a reliability goal that includes the probability of success. Keep in mind that a probability is only meaningful when defined over a specific duration.

[Read more…]

by Fred Schenkelberg Leave a Comment

Environment Element of Reliability Goal

This element of a reliability requirement answers the questions of where and under what conditions the product should operate.

It includes storage, transportation, and installation conditions too. One way to think of the environment is to consider the weather around the device. Temperature, humidity, preoccupation, etc.

[Read more…]

by Fred Schenkelberg Leave a Comment

Use Profile and the Reliability Definition

How a customer uses a product matters. It matters in the amount and type of stress your product receives. It determines the life span. Someone that uses the product often isn’t necessarily going to have a short life span, it might be the lack of use that most damages a product.

[Read more…]

by Fred Schenkelberg Leave a Comment

Function: A Reliability View

We need to understand what a product should do when working to be able to detect when it has failed.

When a function does not perform as expected that is a failure. Being very clear about an item’s function(s) is vital when establishing reliability goals. [Read more…]

by Fred Schenkelberg 2 Comments

Understanding Customer Reliability Expectations

Once asked a customer what they wanted concerning product reliability.

She fully understood that some units will fail, that it’s matter of chance. She seemed understanding of the difficulty creating every product such that none would fail.

Then she confided that all that is fine, as long as the product she buys does not fail. [Read more…]

by Fred Schenkelberg 3 Comments

How to Select Tasks for a Reliability Plan

There are a lot of reliability tools.

From FMEA to FTA, from ALT to HALT, from derating to sneak circuit analysis. We also have a lot of acronyms. We cannot afford to do all the tasks, so which do we select and why?

Each activity has some reason for existing. Each has some question that it helps answer. HALT helps to find what will fail. ALT helps to determine when failures may occur.

Knowing what each tool is capable of doing is a start. Knowing what you need to know is essential.

[Read more…]

by Fred Schenkelberg Leave a Comment

The Meaning of a Failure

Every failure provides information. It provides time to failure, stress strength relationship, process stability and design margin types of information. In every case. Even failures directly related to human error.

A hardware intermittent failure observed by a firmware engineer should not be dismissed. Rather recorded, explored and examined.

A single intermittent failure, or glitch, may indicate nothing other than just a totally random glitch, or a design error that degrades over time causing 50% of units to fail in first three months.

[Read more…]

by Fred Schenkelberg 1 Comment

3 Supply Chain Caused Failures

Some days are better than others. We sometimes run into failure when working to create a new product. With a little investigation we suspect the components are not working as expected.
We’ll call the vendor and ask for an explanation. If this is normal production and variability of performance, our product will suffer an higher than expected failure rate. The vendor will assure us with:

It must have been damaged during assembly or use by us.
It was a very rare manufacturing mistake and won’t happen again.
We haven’t seen this before and you’re the first to report such an issue.
We know about this issue and it’s been resolved in our process.
Must have been an ESD (electrostatic discharge) event.

Not helpful. [Read more…]

by Fred Schenkelberg Leave a Comment

The Want of Modern Customer Service

Reliability and Customer Service

As reliability professionals know, products fail. They fail for a wide range of reasons and over a broad span of time. We know it happens.

This doesn’t help when it impacts us directly though. When we purchase a product or service, it should just work. We know the odds, we know better, yet the sting of failure remains.

Customer Service provides a range of services, one of which is helping customers receive the benefit of their purchase. We call customer service to report a failure and expect their help making it right. [Read more…]

by Fred Schenkelberg Leave a Comment

Minimize Supply Chain Failure Causes

What happens when a product you produce fails? You customer may call and return the product. They may expect you to provide a replacement or refund.
Does it matter if the failure was due to a capacitor or motor that you didn’t design, just purchased?

No.

Does it matter if a supplier’s supplier made an error that directly lead to the failure?

No.

You customer experienced a failure and since the purchase was from you, you are expected to make it right.

[Read more…]