Determining Customer Reliability Requirements
Determining What Customers Really Want Concerning Reliability
Customers want the benefits created by your product. They want the time savings, the reduced yield loss, they want simplicity, coolness, speed, etc.
Customers buy your product to solve a problem, they do not buy it to simply enjoy the features. The features have to do something of value. They have to provide a benefit.
If your product fails, the feature doesn’t work. Customers do not realize the benefit they expected.
In short, your customer wants your product to work as expected. When asked a customer will tell you they do not want to have product failures.
Day in the Life of a Product During Use
In order to design a product that will not fail while in use, you and your team need to understand where and how customers use the product. The where is more than in North America or the Asian market; you need to understand the surrounding environment when the product is in use or storage. Indoor, outdoor, protected, air-conditioned, direct sunlight, etc.
A common technique is to imagine a day in the life of your product. If it is a server providing storage and communication services for your company, it may be humming away 24 hours a day within a climate-controlled computer room. It may see different loads depending on the pace of demands.
A passenger vehicle may see intermittent use with long idly periods over a wide range of daily and seasonal variations. During a trip to work, beyond the engine, steering, and suspension working, the array of indicators, sensors, climate controls, and entertainment systems should also function.
In both cases, the server or the passenger car, we need to understand the range of weather, insect, dust, power, noise, etc. Stresses the system will experience. Along with the range of functional loads, such as packet traffic or CPU use, or road conditions or turning radiuses.
Why Min/Max requirements are Not Sufficient
A listing of the minimum and maximum stress levels, such as -10°C to 40°C, does not capture enough information to make design decisions. It is the expected min/max only. This type of stress description misses where in that range the majority of customers will have products under some value of stress.
For example, a cell phone may have an expectation to operate from -10°C to 40°C, yet how often do users of a cell phone store or attempt to use a phone in such conditions. Rarely.
In some cases, the design has to accommodate the entire range of stresses and encounters sufficiently low failures. In other cases the cost or technology to achieve high reliability over the entire range of expected stress is prohibitive. Therefore understanding the distribution of stress the product may experience provides a means to tailor the design to the majority of users, not the extreme cases.
Environment, Stress, and Failure Mechanisms
There are two ways to look at customer requirements concerning how and where a customer uses your product. First, you can attempt to catalog all the types of environmental and use stresses. This list is long for any product and likely will never be complete.
Second, start with what is likely to fail based on a basic understanding of the use conditions. Explore other potential stresses and if and how they invoke a failure mechanism.
For example, beyond the expected considerations of temperature and moisture exposure, would you consider direct lightning strikes? Depending on your product, say a cell tower mounted device, then you may or may not consider the impact of a direct or nearby lightning strike.
If the ability to withstand specific stress or use conditions is part of normal operation, get the necessary information to understand the relation between the use, stress, and associated failure mechanisms.
If specific failure mechanisms are unlikely to ever occur, do you really need to design to survive those situations? Likely not.
Prioritize, refine, evaluate, and create a product that works for the vast majority of your customers, not every corner case possible (unless that is the intent).
The Impact of Reliability Expectations
Another consideration around customer reliability requirements is the customer’s prior experience and knowledge with similar products. In addition, within systems that may have any different types of products, for example a passenger vehicle, how does your product’s reliability compare to the rest of the nearby systems.
If your radio system is routinely failing while the navigation system works well, by comparison your system is not good enough. Likewise, if your radio routinely outlasts the nav system, you are being shielded from closer scrutiny by your customers.
Consider the impact of out of box, or installation, failures. They sting more than the same failure occurring years after initial use. The expectation for a new product is it should just work.
Furthermore, if prior products have created a brand images based on long lasting, durable products, the new products, even with new and exciting features, should also be as reliable as the expectation.
Marketing and sales discussion provide additional shaping of customer expectations. The product should meet the various promises made during the marketing and sales campaigns.
Having a clear and consistent set of reliability requirements that match the customer expectations permits you to create and deliver products that meet those requirements. Being unclear or ignoring elements of how and what the customer expects places your product’s ability to meet customer expectations at risk (hence field failures).
Asking the Right Questions to Understand Customer Reliability Requirements
When first creating a product or system you should understand the customer reliability requirements. In some industries customers dictate reliability requirements and provide environmental and use conditions. In most industries you will have to estimate or determine customer requirements.
During the development of product requirement documents asking the following questions may assist you to better understand how to set product reliability requirements that will meet your customer’s expectations:
- How long will you (a customer) expect to use this product?
- What is the impact on you if the product fails?
- Where will you use the product most often and on occasion?
- How often will use use the product and for how long each time?
- What are the dominate stresses that may impact the product’s performance during your intended use of the product?
- Do you expect to maintain or repair this system?
These and similar questions help you detail the list of expected stresses related to environmental and use conditions. This set of details will evolve as you define the design of the product and continue to explore the expected range of uses of your product.
Keep in mind that this information during the concept phase of product design is essential for the creation of product requirements. The information on the type and distribution of stress values provide the necessary information for design and development work.
How do you establish and document your customer reliability requirements?