April 6, 1998 Design News
FAST TRACK: MOTION CONTROL
Vintage idea modernizes emerging processes
Intelligent air-bearing design
delivers repeatable precision
by John Lewis, Northeast Technical
Westborough, MA--In its simplest form,
an air bearing consists of nothing more than two accurately
machined surfaces separated by a film of pressurized
air. As surprising as it may seem in this era of rapidly
advancing technology, however, design engineers are
turning toward this rather "old" technology
to solve a variety of problems such as improved precision,
accuracy, cleanliness, and longer life. It also has
helped put a small Massachusetts company, Dover Instrument
Corp., on the map.
Although use of air as a bearing lubricant is an idea
that dates back to the 1800s, it took air-bearing pioneers
nearly a century to successfully implement the concept.
Papers and patents written throughout the 1900s define
modern air-bearing principles, but the lack of modern
manufacturing and computational techniques limited early
work in the field. In fact, practical applications for
the technology didn't appear until the early space program
needed to manufacture and measure components to accuracies
of a millionth of an inch (25 nm).
The cornerstone of Dover Instrument, founded in 1964,
was the work of a small team of engineers from MIT Instrumentation
and Draper laboratories. The team solved the metrology
problem with an air bearing design that ran true to
a millionth of an inch. "The early years were lean,"
says Dover's President and CEO Stephen Hero, son of
Dover's founder, John Hero. "Back then, not many
applications required the kind of micro-inch motion
that air bearings deliver."
Dover's early air bearings were fabricated and assembled
in a 100-sq-ft cubical in a Westborough basement. Most
were used in one-of-a-kind R&D, government, or aerospace
projects. "We've grown from a company that supplied
maybe a hundred components per year, to a present-day
facility that fills 75,000 sq ft. Today we design, manufacture,
and assemble thousands of components and systems annually."
"Driving this growth," says VP of Sales Mike
Townsend, "is micro-electronic and optical product
miniaturization, plus our shift from supplying components
to integrating systems."
Miniaturization drives component features to tighter
tolerances. This increases the number of products requiring
air-bearing accuracy. Flat panel displays, diskdrives,
diamond-turned optics, and semiconductors--emerging
technologies 20 years ago--are now vital to the economy.
Dover's recent 30,000-sq-ft expansion enables manufacture
of hundreds of units to satisfy modern, high-volume
Air-bearing integration. Dover's growth, spurred on
by miniaturization, has also changed the way Dover implements
its air bearings. Previously, customers specified air
bearings with only mechanical accuracy in mind. They
typically mounted a motor, then integrated it into their
machine. Today customers specify not only mechanical
accuracy, but often ask for specific throughputs, accelerations,
and step and settle times.
To address these needs, Dover combines motor, amplifier,
and control technologies into its air-bearing systems.
"That's where most of our technical growth has
come from," says Townsend. To support these technologies,
the company employs close to 200 people, with 40 designers
and engineers, 60 machinists, 60 assemblers, and other
administrative, sales, and marketing staff.
A "long" project may last only six months.
"From a technology standpoint, it's a fast-paced,
exciting place to work," says VP of Engineering
Phil Greene. Employees are exposed to a variety of industries
and technologies. They frequently work on custom projects
that have never been tried before. There's roughly a
40/60 split between standard product sales and custom
design work, where engineers work closely with customers
to implement catalog products into custom machines.
Technological advances and the drive toward
miniaturization in semiconductors, microelectronics,
and optics have propelled Dover?s average
annual sales by 30% over the last six years.
Once an order comes in, a project engineer opens dialogue
to cultivate the relationship, Townsend explains. After
solving customer problems for one product, many customers
return at the end of its life cycle to work on the next
Dover's engineers juggle many projects simultaneously.
"As engineers are shipping one project, they're
supporting products that have already shipped, and designing
new ones," says Greene.
"A core management group meets regularly to make
'big-picture' decisions as to where the company is headed,"
Greene explains. "Once decisions are made, however,
management empowers individual employees to take whatever
steps are necessary to make a better product or satisfy
the customer further," Townsend adds.
Hiring prospects are good for engineers at Dover. The
company hired 65 people last year, 12 were engineers.
Greene looks for engineers with a "can do"
attitude and the ability to think quickly, adapt, and
execute practical solutions. "A company such as
ours depends on team players," Greene says. Engineers
need good interpersonal skills and business sense. "The
hardest part of the job is doing custom design work
with limited time, and understanding that the opportunity
to satisfy a customer may evaporate."
"The schedule can be hectic, and our people put
in a lot of hours. Still there's virtually zero turnover
among employees here," Townsend says. "We
have many employees that have worked here for 10, 15,
or even 20 years."
Despite its rapid growth, Dover strives to maintain
a small-company atmosphere. "We try to keep the
entrepreneurial spirit alive within the company,"
Hero says. The comprehensive benefits and rewards system,
tied to individual and team effort, includes bonuses
and profit sharing.