What-if Analysis

What if you knew all the possible outcomes for your product’s reliability performance due to component variations, for example? What if you knew the future with enough certainty to make a difference?

Building on brainstorming, what-if analysis involved using models or prototypes that allow you to change something and see how it alters the output or performance. What if we change this support bracket from iron to aluminum? What if we swap out this 100 ohm resistor for a 200 ohm one?

As a curious engineer you could spend many, many hours conducting what-if based experiments, so there is a bit more to this idea then just a random walk of changes. [Read more…]

by Fred Schenkelberg 2 Comments

The Quality Triangle and Reliability

How Does Reliability Fit with the Quality Triangle?

The Quality Triangle provides a method to establish priorities for a project. It strives to balance time, cost, and quality (or scope instead of quality). It does not include reliability.

Now I am a bit bias as a reliability engineer and believe a projects set of priorities should explicitly include reliability performance. Of course, there are many potential priorities, yet reliability certainly can make or break a product, it’s market acceptance, and an organization’s profitability.

So, given a quality triangle based set of priorities, how does reliability fit in? [Read more…]

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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…]

by Fred Schenkelberg 2 Comments

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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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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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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Introduction to Design for Reliability

Chapter 7 Design for Reliability of the book Practical Reliability Engineering starts with:

The reliability of a product is strongly influenced by decisions made during the design process.

The key message here is reliability occurs at the point of decision. Each time someone makes a decision, selects a component, chooses a material, assumes a use profile, the eventual product reliability takes shape.

Design for Reliability, DfR, is about making good decisions across the organization concerning reliability. [Read more…]

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Tolerance Specifications Impact on Reliability

Mechanical drawings and electrical schematics communicate the design.

They provide information sufficient to create a product or build a system.

They provide the necessary details that allow others to construct something that originally was only imaged.

We no longer rely on a single craftsman to build a chest of drawers from concept to delivery.

Instead, they may be a team scattered across many organizations relying on the drawings.

Included on the drawings and schematics are dimensions along with tolerances. A keypad will be a specific width, plus/minus some amount. A resistor is nominally 100 ohms, yet anything between 90 and 110 ohms is fine.

Tolerances acknowledge the variability between individual components or caused during the construction process.

Tolerances also impact the reliability performance of your products. [Read more…]

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Inputs to Consider When Setting Tolerances

Technical drawings and electrical specifications often include tolerances.

The range of values allowed for a particular aspect of the part.

Reliability engineers do not set the tolerances, yet we should both understand and influence them.

A critical element of design for reliability is the creation of a robust product.

It is not just robust in the end use, your product should also be robust to the variability that will occur during manufacturing and transportation. [Read more…]

by Fred Schenkelberg 2 Comments

The Basics of Vibration and Shock

Did you shake a wrapped gift as a child?

Sometimes the rattling sound may indicate the hidden contents. A sweater from Grandma would make a muffled sound, while a new Lego set would rustle the many parts.

Your customers may not shake the package to guess its contents, yet your product will experience vibration and shock.

The environments of assembly, transpiration, use, maintenance, etc all include shock and vibration inputs to your product. The operation of your product may include producing vibration and shock loading across the product.

Understanding the basics of vibration and shock will assist you to design your product to operate as expected in the noisy, shaky world.

The rattling about your product experiences is just one of the many environmental and use factors. [Read more…]

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When is DOE Useful?

On page 6 of Statistics for Experimenters, Box, and Hunter suggest a scientist could conduct an investigation without statistics.

Whereas, a statistician could not do so without scientific knowledge.

The text’s discussion quickly expands on the benefits to a scientist when they do employ statistical thinking and tools.

Design of Experiments, DOE, is a set of statistical tools that allow an investigator to efficiently examine multiple factors and their associated influence on results.

DOE allows us to be better investigators. [Read more…]

by Fred Schenkelberg 5 Comments

Analyzing a Taguchi L4 Array Experiment

We’ve collected data and it’s time for the analysis.

As you may recall, in the last article on Planning a Taguchi L4 Array Experiment, we drafted a set of four prototypes. The specific arrangement of factors and levels will now allow us to analyze each factor separately.

The intent is to find the optimal level or setting for each factor, plus which is the most important factor. [Read more…]

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Planning a Taguchi L4 Array Experiment

One of the simplest ways to learn design of experiments, DOE, is to just give it a try.

The Taguchi DOE approach uses orthogonal arrays. This subset of the possible approaches to DOE simplifies the process to create and analyze experiments.

Let’s plan a simple experiment using the Taguchi DOE approach. [Read more…]

by Fred Schenkelberg 8 Comments

The Basics of Derating Electronic Components

As with strength-strength analysis, derating is a means to design robust systems.

Derating is an intentional process applied to every component of a product to reduce the opportunity of a component witnessing more stress than it is capable of withstanding.

The additional robustness also reduces the amount of damage the stress may impart, thus prolonging the life of the component. [Read more…]

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Environmental and Use Factors

The definition of reliability includes four elements.

One of them is the intended environment where the device or system will experience a range of stresses.

The knowledge of where and how an item will operate enables:

The proper design to meet customer expectations
The essential durability during transportation, storage, and use
The complete accounting of applied stresses and their variations
The effective application of stress mitigation or reduction techniques
The efficient installation and monitoring of stress tracking

[Read more…]