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Reactive and Proactive
Do you let events happen to you, or do events f ollow your designs
and expectations? Are you a spectator or actor? Do you wonder
about your products f uture or do you control your products
f uture? Are you reactive or proactive?
Every reliability and maintenance program is a system. Every
program has inputs, such as product testing results and f ield
returns. Every reliability program has outputs, such as product
design and production. In the most basic terms, a reliability
program includes product specif ications f or f unctionality including
expected durability. The program includes some f orm of design,
verif ication, production and f ield perf ormance. Given this basic
lif ecycle description it is possible f or two types of approaches to
executing the product lif ecycle.
Every design will fail
Let’s consider the notion that every product will eventually f ail.
Even the most robust product on Earth will f ail when the Sun
expires. Well bef ore the collapse of the solar system most
products made today will have completely f ailed. The f ailures will
range f rom deterioration of materials, to stress conditions (i.e. lightning strike), or simply to misuse. Some will
simply wear out, others will become obsolete and lose compatibility with other systems; others will simply not
provide suf f icient value anymore.
Another important notion is that upon product design, there are a f inite number of f aults in the design. A
button has a limited number of actuation cycles bef ore accumulated stress cracks the switch dome. A material
has a degradation mechanism (corrosion, polymer chain scission) that slowly deteriorates the material’s
strength. A’bug’ in the sof tware can disable the equipment temporarily. Further, there are possible def ects
designed into the product that do not account f or production variation, user demand or environment
variations, or do not anticipate user expectations. In every case, sooner or later, the design f law will lead to
f ailure. Nonetheless, given only a f inite number of f ailures, it is possible to f ind and remove most design
One way to approach product reliability, and the most common method, is to wait f or product f ailures and then
respond with analysis, adjustments and ref inements in an attempt to improve product reliability. The naive wait
f or the f ailure reports f rom customers bef ore taking action. The team’s logic, if even considered is the
We are good designers
The customer will use the product in unf oreseen environments and applications
If there are customer f ailures we will consider improvements
For some products, with limited release and ample time to redesign the product, this may be perf ectly f easible.
A simple improvement the design team could consider is an estimate of the customer’s use prof ile and
environmental conditions. Armed with this inf ormation, the team then evaluates the impact of the conditions on
the product’s reliability though standardized testing. Setting testing conditions at or slightly above expected
operating environments permits direct evaluation of the design to meet expected conditions. The f aults f ound
would be similar to the f ailure expected to occur in the customer’s hands, and there may be time f or a redesign
bef ore the product is shipped to customers. Carrying out this logic may lead to a broad spectrum of testing
that is both expensive and time consuming.
Part of the logic of product testing includes the thought, “If we test in enough ways over the f ull range of use
and environmental conditions, we should f ind and correct every design f ault.” There is of ten a heavy reliance
on industry standards and common test methods f or every product.
Further improvements to product reliability can ref ine this reactive method, and include using simulations, risk
analysis, and early evaluation and testing of subsystems and components. The overall approach is of ten
limited by knowledge of actual use conditions, lack of test samples, and lack of time.
Moving to a proactive approach can permit the reduction of product testing and the increase of product
reliability. While this may seem similar to the above approach, it involves a f ocus on f ailure mechanisms instead
of test methods. Products f ail because they do not have suf f icient strength to withstand a single application
of high stress (drop, static discharge, etc.) or they accumulate damage (wear, corrosion, drif t, etc.) with use or
over time. Thinking though how a product could f ail by considering the materials, design, assembly process,
and the same f or vendor supplied elements, the product team determines a list of possible f ailure mechanisms.
In this approach not all the f ailure mechanisms will be f ully understood or characterized. The risk in this case is
the decision to launch the product while not understanding the possibility or potential magnitude of product
f ailure. The amount of risk itself is unknown. Theref ore, the proactive team proceeds to characterize the
design or material under the expected use conditions. The intent is to reduce the uncertainty of the risk.
A second result of the proactive approach risk assessment is the rank ordering of f ailure mechanisms by
expected rate of occurrence. One way to accomplish this ranking is to evaluate the stress versus strength
relationships. The items with the largest overlap of the two distributions (stress and strength) indicate they
have the highest potential f or f ailure. The solutions may include increasing strength, or reducing the variance
of the strength.
A third result of the risk assessment is similar to the stress and strength evaluation and includes the impacts
of time or usage on the change in the stress and strength distributions. Either curve may experience changes
to the mean or variance over time. This may be due to degradation, wear, or increased expectation of durability
The proactive approach takes more thinking and understanding of how testing stresses create f ailures, plus
characterization of product designs, materials, and processes, and their related f ailure mechanisms.
In summary, a reactive approach creates a design, and then waits f or f ield returns or standard product testing
f ailures to prompt product improvements. The proactive approach anticipates f ailure mechanisms,
experimentally or via simulation, characterizes the response of the design and materials to expected stresses,
and then designs.
There are other aspects that identif y a reactive versus proactive reliability program. For example, if the only
time management discusses product reliability is when a major customer complains about product f ailures, that
is a reactive approach. If the management team regularly inquires and discusses the risk a particular design
presents to reliability perf ormance– that is a proactive approach.
How does your team approach product reliability? Are the results as expected or are there regular surprises?