A woman takes a polymer boot, heats the
edge of it with a new electric infrared heater about the size of a toaster, and slips it easily on part of a car steering wheel assembly. She still remembers those days when she had to shove the boot on the component to protect it. Some of her colleagues at General Motors' Delphi Automotive Steering Systems in Athens, Alabama, had suffered repetitive stress injuries from this work. But now she and her co-workers like their jobs better because they are benefiting from a new infrared heater developed at ORNL. The new heater expands the leading part of the polymer boot so it can be more easily mounted onto a metal housing in the automotive rack-and-pinion steering assembly. As a result, the number of repetitive stress injuries among workers at the plant has dropped sharply.
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This ORNL-developed infrared boot heater being used at Delphi Automotive Steering Systems has eliminated repetitive stress injuries linked to placing the boot on a car steering assembly.
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According to Aly A. Badawy, director of research and development at Delphi Automotive Steering Systems in Saginaw, Michigan, "The infrared boot heater virtually eliminates the force required to install the boot. This reduction in force results in the elimination of the ergonomic problems associated with placing the boot on the steering assembly." The Delphi managers also like using the ORNL heater in the fabrication process, because when the boot cools, a better seal is made than if the boot had been forced on without heating it.
Since ORNL's polymer boot heater was first tested in November 1998 at the Delphi plant, some two million boots have been mounted using the original prototype infrared boot heater; today twelve newer units are in use there. Interest in the new heater continues to grow. Now, the Ford Visteon automotive parts plant in Indianapolis is considering installing some infrared heaters.
Fabricating hip and knee implants to help people walk without pain is an action-filled process. At the KomTek, Inc., plant in Worcester, Massachusetts, dies used to form a medical implant are incorporated in hammer forges. In this process, a skilled worker uses long tongs to pick up a solid piece of a cobalt-based alloy from a furnace that has heated it to approximately 2400°F. The worker then inserts the piece between two dies and steps on a pedal. A pneumatic hammer smashes the top die against the bottom die with a driving force of up to 25 tons.
Why is such a violent hammering process needed to make an implant? "You can't pour hot liquid metal into a mold to make an artificial hip because the casting will have neither grain flow nor directional strength, allowing the possible formation of metallurgical defects," explains Craig Blue, a metallurgical engineer in the Metals and Ceramics (M&C) Division and a co-inventor of the polymer boot heater. "Hot forging surpasses casting in producing parts that are predictably strong and, therefore, safe and reliable for human use."
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This ORNL-developed infrared insert heater preheats dies at the KomTek plant before medical hip implants are forged.
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However, hot forging has two problems if the
dies are cold. The hot metal hitting the cold metal will not always
fill the mold, making the implant shape defective. Secondly, hot metal
in contact with cold metal causes the die to wear, crack from the thermal
shock, and fail prematurely.
At KomTek a $50,000 set of hip dies lasts
only a few days, producing approximately 1500 hip implants before rework
is needed on the dies. "Unless the dies are preheated to 400°F before
the solid metal is introduced," Blue says, "the manufacturer will initially
get bad implants and the dies will fail prematurely, cutting into the
profit margin. Some medical implant companies have tried using conventional
electric or gas heating to warm their dies, but it takes four hours
and degradation of the dies can result, so most just use cold dies."
But Blue and his associates have developed a possible solution for KomTek:
an infrared heater containing tungsten halogen lamps that preheats the
dies in 10 minutes, not 4 hours. The ORNL heater, which is 30 cm (12
in.) wide and 45 cm (18 in.) long, has worked well for more than six
months at KomTek, indicating that it is industrially robust. It is almost
twice as energy efficient as the standard electric heaters used in hot
forging.
"Our goal is to show that infrared heating improves product
quality and extends the life of dies," Blue says. "Early results show
this is the case."
"We are extremely pleased with results of the ORNL
system," says Michael C. Maguire, vice president for product and process
development at KomTek.
When Blue was a doctoral student at the University
of Cincinnati, he was involved in a NASA project in which he had to
find a way to join silicon-based microsensors. Because he needed to
get them to high temperatures fast, he used tungsten halogen lamps,
which go from cold to full power in 0.75 s and can be shut down instantly.
This type of electric lamp provides radiant heating by emitting infrared
radiation from a fine tungsten filament resistively heated in a quartz
envelope containing argon or a halogen gas. Blue then began designing
furnaces using tungsten halogen lamps for different materials projects.
When Blue came to ORNL in March 1995 as a
postdoctoral researcher, he worked with group leader Vinod K. Sikka
and many others in the Materials Processing Group to guide the construction
of a tungsten halogen lamp furnace. The furnace was built by Barry Whitson,
Kenneth Byrd, and Larry Smarsh of ORNL's Plant and Equipment (P&E)
Division. The start of this project was made possible by programmatic
support from ORNL's Advanced Industrial Materials Program, managed by
Peter Angelini, and from the M&C Division. Because of this equipment,
Blue, Sikka, Evan Ohriner, Srinath Viswanathan, and Ted Huxford, in
cooperation with many others, have brought in $3.7 million in industrial
and DOE funds to support infrared heating research projects. Now Sikka's
Materials Processing Group and other engineers are further developing
the technology for materials research.
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Views of the powerful plasma arc lamp at ORNL's Infrared Processing Center. |
Blue spearheaded the development of ORNL's
first-generation Infrared Processing Center. Additions to the center
are continuously being made. The heart of the center now is a plasma
infrared system capable of delivering 3500 watts (W) per square centimeter.
It was installed by Whitson, John Norris, and Bill Fellows of the P&E
Division.
In addition to the polymer boot heater and the die
heater, Blue and his M&C colleagues Sikka, Ohriner, Viswanathan,
P. Gregory Engleman, and David C. Harper are developing coatings to
extend the life of industrial dies for casting automobile parts. The
coating research and other work have required the development and installation
of the world's most powerful lamp. This 300,000-W stabilized plasma
source of radiant heating, built by Vortek Industries of Canada to meet
ORNL specifications, is now attracting even more industrial interest
in the Infrared Processing Center. For example, Caterpillar and B. F.
Goodrich representatives have already visited it.
"We are using the plasma arc lamp to develop coatings for
casting dies," Blue says. "Coatings are needed for aluminum dies used
to make auto parts. These dies are fitted with H-13 steel pins used
to make holes in the cast part so they don’t have to be machined in,
saving money. These dies are placed in an H-13 steel housing. The problem
is that when liquid aluminum is injected into the dies, it reacts with
the H-13 steel, degrading it and gradually making the die unusable."
Using the plasma source, Blue and his colleagues have come up with a
chromium carbide coating that protects H-13 steel from attack by liquid
aluminum. "We are finding that by using our powerful plasma lamp to
precisely and rapidly heat a precursor material on the H-13 steel, we
can make coatings that fuse with the substrate without changing the
base material properties," Blue says. "Because the intense radiant heating
sets up large temperature gradients so fast, the iron in the H-13 steel
will have almost no time to dissolve. Thus, heat treating of the coated
component will not be necessary. We are testing these coated dies at
Tennessee Tools to see if the coating allows the dies to last longer."
Besides making medical implants and automotive parts, the U.S. forging
industry, a $6 billion enterprise, provides truck, aerospace, and agricultural
equipment parts; valves; fittings, and industrial tools, all of which
are essential to the U.S. economy. Degradation of dies and other tools
used by the custom forging sector of the industry is a major economic
problem. As the Infrared Processing Center at ORNL finds ways to extend
the life of dies, the custom forging and die casting industries are
likely to warm to the DOE user facility.
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