Americanmachinist 2063 82689satellites00000054844

Shops on a Power Trip

Oct. 17, 2008
Uranium-enrichment project calls on local jobshops for precision machining
ARMEC’s satellite shop supplies unclassified components and grooms highly skilled machinists for USEC’s uraniumenrichment program.
USEC's larger and highly productive centrifuges.

Even in his wildest dreams, “Big Ed” Green probably never imagined that his small backyard machine shop one day would be machining parts for a project that is designed to drastically reduce America’s dependency on foreign-supplied enriched uranium to fuel nuclear power plants.

The project, run by USEC Inc. (, involves using technologically upgraded centrifuges that enrich uranium by separating uranium 235 and uranium 238 via centrifugal force.

USEC’s centrifuges are larger and more productive than any existing units working in foreign countries.

The company manufactures many of the metal parts and sub-assemblies for its centrifuges at the American Centrifuge Technology and Manufacturing Center, a facility in Oak Ridge, Tenn.

The centrifuges measure about 43-ft tall and about 24 in. in diameter, and the company expects to have 11,500 of them in operation at its American Centrifuge Plant, in Piketon, Ohio, at the end of 2012. The current goal is to produce several hundred centrifuges per month.

At the Oak Ridge plant, Babcock & Wilcox (, one of USEC's strategic suppliers, is in charge of producing all the metal parts for the centrifuges. Babcock & Wilcox manufactures most of the parts itself, especially all the classified ones.

“At first glance, the machined centrifuge components don’t seem so complex, but their tolerances are extremely tight, making machining much more difficult and requiring that they be 100 percent inspected. Plus, materials used for the parts pose temperaturecompensation challenges,” Carl Durham, president and general manager of Babcock & Wilcox operating at the American Centrifuge Technology and Manufacturing Center, said.

Due to the large scope of the project, Babcock & Wilcox farms out unclassified work to over 40 sub-contractor shops, two of which are ARMEC ( in Knoxville, Tenn., and Oak Ridge Fabricators Inc. ( in Oliver Springs, Tenn., the shop “Big Ed” Green started back in 1989.

“Both ARMEC and Oak Ridge Fabricators are prime examples of shops that grew their capabilities to match USEC’s needs,” Ben Jordan, manufacturing development and integration manager at USEC, said.

According to Jordan, Oak Ridge Fabricators stood out as a high-quality, low-cost shop extremely focused on customer service. Prior to Babcock & Wilcox coming on board the project in early 2008, USEC began working with Oak Ridge Fabricators in 2001.

USEC initially awarded the shop some general low-volume machining work that it completed on time and at reasonable prices. The shop even worked nights and weekends when the USEC parts were needed immediately.

“After awhile, Oak Ridge Fabricators noticed the work from us that they weren’t getting to bid on, and that motivated the shop to expand its facility and add the equipment necessary to win the higher-level work they weren’t getting,” Jordan said.

Sadly, “Big Ed” Green passed away in 1998 and never got the chance to see his jobshop expand, win high-level USEC work and flourish under the management of his eldest son Edward “Scot” Green together with Operations Manager Doug Zink, Scot’s brothers Matt and John, and their mother Phyllis, who now owns the business.

Doug Zink, Matt Green, Scot Green, and John Green, all of Oak Ridge Fabricators, in the shop’s new “high-precision” section that was established to win more jobs making uranium enrichment centrifuge components.

Oak Ridge Fabricators is a turning shop that does a lot of big O.D. and I.D. work. Average job runs number 500 or so pieces.

Scot said that, in a nutshell, the shop needed higher-precision machines – mainly turning centers with live tooling — and better part inspection capability to win more USEC work. Initially, Oak Ridge Fabricators installed two Mori Seiki ( turning centers with live tooling that Scot said drastically increased the shop’s production and boosted part accuracy, along with the shop’s partmachining capability.

“If you don’t have live tooling capability, you are behind. Today’s tolerances make it tough to move parts from one machine to another to complete them and still meet a tight tolerance. Live tooling changed our world. We are no longer chasing tolerances. And we now go after high-precision complex work to avoid losing jobs to foreign suppliers,” Scot said. But, he added that the USEC work was what really pushed the shop into high precision.

Oak Ridge Fabricators added a new wing, specifically for high-precision work, to its existing facility.

The new wing houses several new Mori Seiki machines and an inspection room with a high-end, Carl Zeiss Inc. ( CMM.

The shop now has four Mori Seiki machines, the latest being a DuraVertical 5100. And it is planning to add an NL 3000 turning center with Y-axis capability and live tooling for handling parts as large as 16 in. in diameter.

“The USEC work is a big deal for everyone involved, and we want to be involved to the end. For that work, we have to quarantine material, track everything involved the minute it comes through the door, develop quality documents and get approval from the USEC quality team,” Scot said.

He estimates that, as a result of the USEC project, he’ll have to add 10 more employees to shop’s current 28 and that the work may t r ipl e the $2-million-a-year shop.

“We have to grow slow. Everything is evaluated and re-evaluated. To us, machine tool purchases are a big deal. They are planned for and precisely executed. Shops have to have the machining capabilities to sell themselves, but you should either have the work to pay for new equipment or the ability financially to pay for it upfront,” Scot said.

Just as Oak Ridge Fabricators grew to meet USEC’s manufacturing needs, so too did ARMEC, a shop that started with two employees, and now is a large machining and engineering group that runs the machine tools USEC owns, while maintaining a satellite shop where it also machines unclassified parts for the project.

At USEC’s American Centrifuge Technology and Manufacturing Center, there is a building called the Centrifuge Technology Center. That is where ARMEC comes in.

ARMEC was hired to evaluate machines, develop machining processes for classified parts and to incubate highly skilled machinists for the project.

ARMEC conducts its development machining in the Centrifuge Technology Center, then, once perfected, the processes move to the American Centrifuge Technology and Manufacturing Center, where they are replicated for highvolume production. ARMEC works for Babcock & Wilcox and, under that umbrella, will continue to do development work, but will also be integrated into the team that will run the high-volume production.

For high-volume part production, the American Centrifuge Technology and Manufacturing Center provides 300,000 sq.-ft of space under roof, and is already equipped with some machining and inspection systems.

“We are doing a lot of automation with machining centers and have EDMs, lathes, mills, mill-turns and grinders already in place. Eventually, the facility will house well over 100 machine tools,” Babcock & Wilcox’s Durham said.

However, not all machine tools can make centrifuge parts. A machine has to be as actively accurate as possible for not just one part, but for long production runs, Mike Tuck, president of ARMEC, explained.

“When we produce a part, we have to control all the variables, from setup to tooling to the machine tool, which is the most significant variable in the process because thermal and positioning errors can work against you. Some of our parts have over 100 features that have extremely close dimensional and form tolerances,” Tuck said.

The goal at the Centrifuge Technology Center is to remove machine tool error from the manufacturing equation and, according to Tuck, Mori Seiki machine tools allow the center to do that.

All USEC Mori Seiki machines, as well as the Zeiss CMMs for the project, came from Mori Seiki distributor J&H Machine Tools Inc. ( in Charlotte, N.C. and Brentwood, Tenn. J&H also supplied all of the Mori Seiki machines and Zeiss CMMs to ARMEC’s satellite shop and to Oak Ridge Fabricators.

J&H also did the installation and integration of automation and inspection equipment at the American Centrifuge Technology and Manufacturing Center. According to Rob Johnson of J&H, working with USEC was tricky to say the least.

“Its ultimate goal was to find ‘perfect’ machines that could take the machine as far away from the accuracy issue as possible. If there was a problem, USEC wanted to know that it was workholding or tooling – not the machine itself,” he said.

To find machines as close to perfect as possible, USEC made a series of test parts.

“None of the parts resembled what the actual parts looked like, but they created interesting challenges that tested a machine’s capabilities. Upon closer examination, we could see where the challenges were,” he added.

“Shapes and splines with close tolerance bands were placed in different positions to specifically check ballscrew reversal, and large test parts helped to determine how well a machine could hold accuracy continuously from large to small diameters. The parts also tested a machine’s multi-axis contouring accuracy,” Johnson said, adding that the Mori Seiki machines were the only ones that went through USEC’s vetting process with 100 percent success while accomplishing tasks that Johnson himself didn’t even think were possible.

Latest from Machining / Cutting