Creating reliable products isn't easy.
If you don't believe that, then consider North American automakers.
In the past decade, GM and Chrysler have dedicated themselves to boosting quality.
They've hired scores of full-time reliability engineers, many with Ph.D.s. Yet
they've continued to play catch-up with the Japanese.
The trouble is, reliability is a fast-moving, slippery target.
In telecommunications design, for example, engineers have to allow for so-called
"five nines" uptime, meaning that their equipment must work for all but five
minutes per year. That even includes those minutes when maintenance workers are
replacing circuit boards. If the engineers don't accomplish that, their product
is deemed a failure.
Or consider the dilemma of automotive designers: Their products must run in temperatures
ranging from -70F in Barrow, AK to 130F in the Arizona desert. They have to work while
driving over gravel roads or washboard concrete. Worse, they have to operate
reliably, even when they are poorly maintained by owners who seem oblivious to
their requirements. If the engineers don't accomplish that, consumers complain.
The bottom line is that design engineers have to know
failure modes. They have to conjure up potential ways for users to abuse their
products. They have to imagine ways for assemblers to misassemble their parts.
"You hear people say, ‘This must be a Friday car,'" notes
Jake Fisher, senior automotive engineer for Consumer
Reports. "Well, if you design it right, it shouldn't matter what day it's
built on. You have to design it so it can only go together one way."
Here, we've collected recommendations from engineers who
study reliability on a daily basis. We've also culled through some back issues
of Design News and cited some
strategies that have worked for engineering teams in the past. Following are a
few of those strategies.
Don't be too anxious to redesign good products.
Earlier this year, Ford Motor Co.'s Focus and Fusion vehicles outperformed
products from Toyota
and Honda in Consumer Reports' evaluations.
How? Ford stuck with a model that was already competitive, then
concentrated on its processes. The Focus, for example, came out in 2000
and its reliability was poor. Each year, though, it got better. "Ford's
not redesigning them as fast as some of the other manufacturers are,"
Fisher says. "When it comes to reliability, slow and steady often wins the
Never assume anything is obvious. What
appears to be obvious to a designer may not be so obvious on the factory
floor. When designers assume too much, products often get misassembled. "It's
hard for designers to imagine that everyone might not be thinking the same
way they are," notes Paul Nickelsberg, president and CTO of Orchid Technologies, a consultant
that specializes in electronic product design and development. "In actual
fact, nothing is simple and obvious on the factory floor. The workers are
not mind readers."
Concentrate on perfect systems, not
perfect components. After years of studying Japanese car makers, the Center
for Automotive Research reached an amazing conclusion a few years ago:
If you assume you'll get better
quality by demanding excruciatingly tight part tolerances, then you're
destined for second-class performance. High reliability, they learned, is
dependent on perfect systems, not perfect components. "It's
counter-intuitive," says David Cole, the Center's chairman. "It doesn't
appear to make rational sense, but if you can build with repeatable,
imperfect parts, you can solve a lot of quality problems at the systems
Don't pack more functionality into one
button just because you can. The beauty - and the curse - of software
is that it endows products with many capabilities. But users are often
flummoxed by the multitude of features available in a single button or
knob. As a result, they sometimes end up complaining that such buttons and
knobs don't work properly. "Today's automotive cockpits are sleek
looking," Fisher says. "But they've replaced buttons with software, so the
user has to go through a bunch of menus. Many consumers don't like that."
Know the appropriate standards.
Especially in power systems design, standards are key. "In power
electronics, there are standards that have to do with creepage, clearance,
component ratings and de-ratings, and minimum distances between parts,"
Nickelsburg says. "If you follow those, it could lead to other issues you
haven't thought of, and it could boost your reliability."
Understand interaction failure modes.
Mismatch two perfectly good components and you may create an unreliable
system. If, for example, a starter motor lacks the necessary torque to
start an engine, it will soon wear out. Why? Because longer cranking wears
it out. Similarly, a car's heavy glass window may reduce cabin noise, but
it can also wear out the power window motor regulator. The bottom line is
that many components work fine by themselves, but they can cause problems
if no one considers how they go together.
Track performance of all vendors.
It's not good enough to track the performance of your main suppliers, says
Cole of the Center for Automotive Research. You should also track your
suppliers' suppliers, as well. He recommends that manufacturers keep
performance lists of all vendors, from tier-one on down.
Be aware of program timing. One of
the biggest causes of poor reliability is missed schedules. Why? Because
engineers who fall behind often find they don't have enough time to fix
potential problems. Are the dies on time? Are the sub-systems getting
validated? Are system assemblies passing internal tests? If you don't know
the answers to those questions, reliability will suffer.