Your Reliability Engineering Professional Development Site
Ideally, in every design of every component, the stress–strength relationship looks like this figure. The stress is well below the strength.
This implies there is very little chance of failure due to the element being overstressed.
Also, ideally, we fully characterize all stresses and all strengths for each element of a product. This is generally difficult to accomplish and it is rarely done to that extent.
Every once in a while I see a comment that by following the HALT methodology you will “over design” a product.
Many question at what point or operational limit do you quit increasing the stress-strength margins. Those who hold this view of HALT do not understand the essence of what was Gregg Hobbs’ principles and paradigm shift. [Read more…]
Embarking on a product development project contains many aspirations, including that the product should work as expected.
The device functions and does so over time. Enough time for the customer to deem the device reliable.
That is one way to approach setting a reliability goal for a project. Estimate what will delight the customer. Set a target for how long without failure your new design function.
The goal provides a focus for the team. [Read more…]
You may already know my position on MTBF.
If not, in short, do not use MTBF at all, ever, in any form. So what should we use instead?
I suggest using reliability, the probability of success over a specific duration.
Let’s discuss what will work for you.
Reliability or life testing involves estimating the expected durability over time of an item.
This may be an entire system, a product, or an individual component. We may also focus on an element of a component, such has a material property.
At the end of the testing, we want to say something meaningful about the expected performance over time. [Read more…]
A common question concerns the warranty period.
How long should we, the manufacture guarantee that our product will work as expected? Do we include limitations or not? How do we decide? [Read more…]
Highly Accelerated Life Testing (HALT) is a technique to expose weaknesses or faults with a product.
HALT uses individual or combined stresses in a step stress approach to quickly apply sufficient stress to reveal defects.
HALT is not a specific chamber or fixed set of test conditions. It is an exploratory process to reveal weaknesses in a design.
The product development process naturally includes a check step, to determine if the expected functions of the product work as expected.
Some teams then add a measured amount of stress (temperature, vibration, dust, load, etc.) to the product to explore functionality at elevated stress levels. [Read more…]
Here’s a short list of terms related to warranty management. Often is the words we use that matter and understanding the language of warranties is one step in mastering warranty management.
A promise made to the buyer of an item that the manufacturer (seller) will repair or replace the item if necessary within a specific time period. [Read more…]
In short, you probably do, better reliability performance the better the brand image.
When I’m making a purchase I prefer to buy items that I either have personal experience work well over time (reliable) or have many comments and reviews noting the durability.
As a reliability engineer, I am often asked what kind of car I drive (a Toyota Highlander, if must know). Reliability does matter -not only to me- it matters for many making a buying decision.
When a product’s actual reliability performance exceeds the customers expected reliability performance, the customer may consider the product reliable. This experience builds and when supported by other experiences from the same brand, increases brand equity. High brand equity permits a price premium, increased brand loyalty, and increased positive word of mouth support. [Read more…]
When making a transaction there is an element of trust.
The buyer is trusting you are providing a product that lives up to the claims provided. Neither party wishes to be duped. Yet, we do enter into transactions. We buy stuff.
A few hundred years ago and prior most purchases were from someone you knew, and most likely knew well. It was in the craftsman’s best interest to maintain honest dealing and create quality products. If not, they would enjoy less business. [Read more…]
Why do so many avoid failure?
In product development of plant asset management, we are surrounded by people that steadfastly do not want to know about or talk about failures.
Failure does happen. Let’s not ignore this simple fact. [Read more…]
In many parts of the world ‘caveat emptor’ [let the buyer beware] no longer applies.
The producer and distributors of products are liable for their products.
This extends beyond product failures and a warranty claim. Today the company is liable for to make right any loss or damage incurred by the use of the product.
Courts and laws around the world reflect the protection of users of products from adverse consequences due to a negligent design and assembly practices.
The producer of a product must consider the user’s safety and provide reasonable safeguards.
This applies even when the user misuses or abuses a product. [Read more…]
Everything varies.
Your vendors provide components with a range of values. Your production process varies, too.
Creating, monitoring, and maintaining process stability enhances your product reliability performance.
When I started my professional life as a manufacturing engineer, a senior engineer told me we take a product design and can only make it worse.
He said if we could make every unit exactly according to the nominal values of the drawing, every unit would work well. [Read more…]
Early and often during product development, the team needs to know the expected reliability performance of the current design. The values provide information to make decisions.
We have the ability to create meaningful estimates. Or, not.
The operating characteristic curve, OC curve, visualizes a sampling plan.
At times, we select a sample from a group of items and evaluate them. Does this lot of widgets meet the specifications? Does this batch measure up? [Read more…]