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CRE Preparation Notes

Prep notes for ASQ Certified Reliability Engineer exam ISSN 2165-8633

The CRE Preparation Notes series provides you with short practical tutorials on all the elements that make up the ASQ CRE body of knowledge. The articles provide introductory material, basics, how-tos, examples, and practical use guidance for the full range of reliability engineering concepts, terms, tools, and practices.

Keep your knowledge fresh by regularly reviewing topics and tools that make up reliability engineering.

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You will find the most recent tutorials in reverse chronological order below.

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Temperature & Humidity Accelerated Life Testing

Temperature & Humidity Accelerated Life Testing

Peck’s Relationship

High temperature & humidity is a common test condition. For specific failure mechanisms, there are models available (or you can create a model) to determine the translation from test to use conditions.

These acceleration models generally only apply to one specific failure mechanisms and do not apply to a system level estimate of life. If the failure mechanism is the dominant failure mechanism for the product, then an ALT exploring just that mechanisms would provide a life estimate.

Peck’s relationship is an acceleration model for the effect of humidity on the metallization elements of integrated circuits within plastic enclosures (typically an epoxy over molding).  [Read more…]

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Time Compression Accelerated Life Testing

Time Compression Accelerated Life Testing

The Easy One

The easiest ALT is one that you operate an item more often then operated by the customer. Removing spans of time the item is not being bent, moved, heated, etc allows you to use time compression.

For example, a home kitchen toaster may be used for a few cycles during breakfast time in your home. In the lab, we can avoid having to wait the day of idle time and just make toast more often than just at breakfast to accelerate the operation of a toaster.

Time compression ALT is also easy to understand and describe the acceleration factor to cover the ALT results to field use conditions. Let’s explore a simple example, work out the acceleration factor and how to interpret a set of ALT results. [Read more…]

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4 Different Types of Reliability Testing

4 Different Types of Reliability Testing

Getting the Right Information from Your Reliability Testing

You cannot test in reliability any more than you can test in quality. Often reliability testing is done though, and knowing the range of testing approaches and their associated results will help you get the most information from each test conducted.

Let’s explore the types of testing that generate information useful as you develop a reliable product. There are 4 different types of reliability testing:

  1. Discovery
  2. Life
  3. Environmental
  4. Regulatory

Within each type there are many variations to the testing details and the specific results generated. Understanding the questions each type of testing has the capability to resolve is a good first step to implementing the right set of tests for your project. [Read more…]

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4 Steps to Accomplish HALT

4 Steps to Accomplish HALT

4 Not Always Easy Steps

Highly Accelerated Life Testing, HALT, is a method to discover the weaknesses in a design. Using a step stress approach of single and combined stresses, you can quickly expose the salient weaknesses in your design and/or assembly process.

The value of HALT is it’s quick and often finds problems not previously known. You will destroy one or more prototypes, yet the value of knowing specifically what needs improvement more than justifies the sacrifice of a few photos.

Conducting HALT may be part of your reliability plan. Keeping a few steps in mind will help make sure your HALT does provide value back to your development efforts. [Read more…]

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Taguchi Design of Experiments Approach

Taguchi Design of Experiments Approach

Dr. Taguchi was an engineer, not a statistician. He considered the ability of design of experiments (DOE) to identify and reduce sources of variability, yet needed a system that did not require a statistician to implement.

Dr. Taguchi proposed a few considerations for those applying the Taguchi design of experiments approach. [Read more…]

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Taguchi’s 3 Fundamental Concepts

Taguchi’s 3 Fundamental Concepts

Taguchi may be best known for the variation of design of experiments that bear his name. Yet the impact of his work is felt across the product life cycle and all of the quality field.

Building on Deming’s observations that 85% of poor quality is due to faulty processes and only 15% due to the worker, Taguchi focused on creating robust processes.

A robust system is one that tolerates the daily and seasonal variations of the environment, machine wear, and equipment part-to-part variation, etc. A robust system operating in the range of real world conditions. [Read more…]

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You Are a Reliability Leader, Now Make a Difference

You Are a Reliability Leader, Now Make a Difference

Your Reliability Engineering Leadership Role

Leadership is not a position or title within an organization. It is an attitude.

You’ve seen the internet meme’s about the difference between leadership and management. There is a difference and while not everyone is going to be in top management, everyone can (and should) be a leader.

As a reliability professional, you are conveniently looked to for leadership. You are expected to use your knowledge and skill to solve problems. To help teams solve problems. To improve the reliability performance of your system and across your industry. [Read more…]

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Introduction to the Quality Triangle

Introduction to the Quality Triangle

Priorities and Balance

Have you ever worked on a project with no deadlines, unlimited resources, and boundless scope? Probably not.

Quality Triangle-1
The Quality Triangle

You may have worked under the guidelines of a quality triangle, also known as a project management triangle, iron triangle, or project triangle.

Why is that? Why the limits to our ability to create a product or improve a system?

First, the world we work and live within has limits. We have only so much time for work, only the available resources, and limited knowledge. We do our best with what we have to work with at the time.

Second, as I once was told while working on an accelerated test design, ‘if there isn’t a deadline, you’ll happily tinker with the plan and get the testing done.’ My boss was right of course.

The set of constraints shape our projects and products. By understanding the set of constraints, specifically how they frame decisions, then we can complete complex projects. [Read more…]

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Using Reliability Goals to Set Requirements

Using Reliability Goals to Set Requirements

Customers of your product would like the particular one they have to work. To work over time.

If a product meets the customer’s expectation by working as long or longer than they expected it to do so, then they may consider your product reliable.

We use reliability goals to discuss the customer’s reliability expectations. It is the establishment of requirements that converts the customer expectations to development and production obligations. [Read more…]

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Uncertainty and Risk Management

Uncertainty and Risk Management

We are rather good at being surprised when setting expectations for the future. This is the essence of risk. The difference between what we expect to occur or would like to occur, and what does occur.

The definition of risk in ISO 9000:2015 and ISO 31000 include the phrase “ effect of uncertainty”. Let’s remove some of the uncertainty around the term uncertainty in the context of risk and risk management. [Read more…]

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The Connection of Reliability and Customer Expectations

The Connection of Reliability and Customer Expectations

Customers Experience Product Reliability in Real Time

In a customer’s mind, the product works or it doesn’t. If it doesn’t work as expected it has failed. This may or may not be a reliability problem.

A customer or someone using your product brings a set of expectations to the experience. The range of expectations may range from very little to very high functioning, value production, and durability.

Failures are defined by customers.

In part, this is the functional capability, the operating within specifications, and the durability. The customer’s definition of reliability may or may not follow the design specifications.

It is the comparison of what should happen to what does happen. [Read more…]

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Performing the Right Corrective Action

Performing the Right Corrective Action

Performing the Right Corrective Action

When something doesn’t work as expected, it is a failure. A common response to a failure by an organization is to restore the system or remedy the situation.

Each failure is unique to the product, industry, customer situation, expectations, etc. Selecting the appropriate response or corrective action when confronted with a failure may or may not be obvious.

Selecting the right corrective action depends on the business and legal factors, along with customer expectations.

For a given failure, thinking through the range of possible responses and selecting the right one takes care to meet the various stakeholder’s requirements or expectations. [Read more…]

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Building and Using a System Reliability Model

Building and Using a System Reliability Model

From the simplest to the most complex system, building and using a reliability model permits the entire team to make better decisions.

Understanding and monitoring system reliability involves knowing both:

  1. the reliability of elements within the system,
  2. as well as how the elements relate to each other reliability-wise.

We use system reliability models to identify weak links, and focus resources, to meet our desired reliability goals.

Being able to build the right model to meet your team’s needs best is one of your roles as a reliability professional. [Read more…]

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The Many Ways We Use Variance

The Many Ways We Use Variance

The term variance is a statistical concept related to the spread or dispersion of a set of data. Second to the mean, it a common value we may calculate.

We find standard deviation easier to understand and use (it uses the same units as the data) whereas variance uses the units squared.

We use variance in quite a few different ways. Let’s review just a few. [Read more…]