This technical information has been contributed by
Stewart EFI

Old-School Stamper Knocking Out Next-Gen Parts

A collection of Stewart EFI stamped parts for use in the automotive, medical, and aerospace industries. Photo courtesy of Stewart EFI.

Stewart EFI's deep roots in American manufacturing spread out into the South and China, with OEM parts for automotive, security, medical, electronics, aerospace, and industrial, among others.

By Mark Langlois, Senior Editor

How is Stewart EFI, an 80-year-old precision metal stamping company, able to provide millions of parts from factories in Connecticut and Texas when other companies are shipping those quantities of work to China?

John D. Labas, vice president of sales and marketing at Stewart EFI, believes that quality is the answer.

"You see those people out there?" Labas asked, looking at the shop floor during a tour of the company's headquarters in Thomaston, Connecticut. The sprawling factory in the Naugatuck River valley comprises a series of interconnected units, each section echoing with either slow, heavy thumps of 200-ton stamping machines or the tap, tap, tap, tap, tap of lighter stamping equipment. "They're a team of highly skilled, experienced tool makers, technicians, and engineers focused on precision, high quality, and efficient production. What you don't see out there is unskilled labor."

Stewart EFI's skilled workforce manufactures value-added precision stamped metal parts, including deep drawn, progressive die, and slide-formed metal components, while also providing wire forms, automated and secondary assemblies, plating, and metal finishing services. All of Stewart EFI's facilities are ISO 9001 and TS 16949 certified, and the company has recently received quality awards from 3M, Denso, and General Motors, said Labas, who credits the awards to the company's "robust systems" and the "people who diligently monitor them." He calls Stewart EFI's employees its "greatest single asset."

"The technical skills of our toolmakers, machinists, design engineers, manufacturing engineers, quality technicians, and manufacturing supervisors are unsurpassed. They are the key to our ability to consistently supply technically challenging, tightly toleranced components at high volumes to some of the most demanding and respected international companies," he told D2P. Because people with these skills are becoming increasingly difficult to find, Stewart EFI instituted a fully accredited apprenticeship program to train those with the desire to enter manufacturing and learn the toolmaking and machinist trades.

Craftsmen-Like Detail Cherished by Next Generation

Inside the company's sprawling 104,000-square-foot headquarters are tool and die rooms with clear windows attached to each stamping area. Inside the shop's tool and die rooms, journeymen tool makers use and covet worn Gerstner oak tool chests with polished brass hardware, relics of a bygone age that are still manufactured for journeymen in Dayton, Ohio.

"We have an apprenticeship program, and that's the first thing they want (a Gerstner tool chest) when they graduate," Labas said. Eight students are currently enrolled in the state-certified program. "A young person gets out of the program and, with overtime, can earn an annual wage as good as or better than many college graduates. That's without any college debt. You're talking about a 24- or 25-year-old with the ability to buy a house. There is also renewed interest in manufacturing when we go to the local high schools or to UConn or Central [Connecticut State University]."

A Stewart EFI design engineer and toolmaker discuss a new tool design. Photo courtesy of Stewart EFI.

Stewart EFI has been in the stamping business since 1936, using its core processes– deep drawing, progressive die stamping, and slide forming– to make parts for numerous industries. The company provides parts to Tier 1, Tier 2, and aftermarket automotive suppliers for use in air bags, body and exterior components, brakes, electronics, emission controls, engine management, fuel handing, and fuel injection. The company also makes parts for use in infotainment, instrumentation, interiors, safety, and suspension applications, among others. In addition to automotive, Stewart also stamps parts for industries that include electrical, electronics, medical and dental, batteries, HVAC, appliances, and others.

Stewart EFI's main manufacturing facility and headquarters in Thomaston, Connecticut, are supplemented by manufacturing plants in El Paso, Texas, and a joint venture in Hangzhou, China. The Stewart Stamping Corp., founded during the Great Depression as a stamping firm in the Bronx, New York, merged with Eyelets for Industry, in Waterbury, Connecticut, in 1999, to become Stewart EFI. Today, Stewart EFI employs 250 people in its three U.S. facilities, with 10 engineers and over 50 tool and die makers. Both companies were founded by entrepreneurial and skilled toolmakers in hopes of growing a thriving business.

Looking For New Opportunities from Existing Parts

"At our multiple locations, we have over 60 deep draw transfer presses, including U.S. Baird, Waterbury Farrel, Asahi Seiki, and Minster, with up to 200-ton capacity," said Labas. "This equipment allows us to make parts up to 5.75 inches (146mm) in depth with a maximum blank size of 8 inches (203mm)."

Stewart EFI specializes in what it calls "conversion opportunities," where it will offer a prospective customer a more efficient, less expensive method of manufacturing its part while ensuring high quality.

Critical to this effort is the engineering support that Stewart EFI offers its customers. Although they cannot tell their customers how to design their products, Stewart can impart its knowledge of metal stamping and how to minimize cost, improve quality, and provide a part better suited to their subsequent manufacturing process, Labas said.

"We offer the opportunity for our customers to convert components made in other, more expensive processes– such as machining, casting, forging, and fine blanking– into stamped components with significant cost savings," he explained. "Our engineers work collaboratively with our customers' engineers to assess if the conversion to the stamping process requires part design changes to achieve the cost savings opportunity."

"We're always looking for these types of conversion opportunities," he added during the factory visit. "Our sales force is out in the field: They're sales engineers, they have a technical background, and if they see something and it's evident that it could be drawn, they say, 'I think we can make these. How are you making that now? Can I get a drawing? Can I get some samples?'"

Procurement and engineering departments always want less expensive parts. They are willing to share the information to lower costs, Labas said. For example, a former supplier to one of Stewart EFI's customers welded a part together and, in a second process, machined two holes into the part. Taking advantage of a conversion opportunity, Stewart now stamps and side-pierces the medical surgical piece in one step in a standing order of 5 million parts a year. The part is a tube about 4.25 inches long and about 7/16 inch in diameter.

"It's a housing for a surgical, medical device," Labas said. The actual part and the OEM it's made for are protected by non-disclosure agreements.

"In this case, because it's such a severe deep draw in stainless steel, you're putting a lot of internal stress into the material. As part of our finishing operation, we basically stress-relieve the part. We stabilize the function. There is engineering involved in doing that and working with the engineers at the device manufacturer around dimensions to make sure all thicknesses are ideal," Labas said. "We make sure that functionally, it is completely adequate for their needs. It is also cosmetically nicer because you don't have the welded seam.

Two deep-draw stamped parts that hold a medical-surgical device. Photo courtesy of Stewart EFI.

"What we were able to accomplish was to change it from a different manufacturing method, a costlier manufacturing method, and produce it nearly complete right off of one press without the expensive secondary operations," Labas added.

Stewart EFI uses its deep draw stamping process to shape the tube from a round disk of stainless steel. The press draws in the stainless-steel strip in a series of operations within the press, while maintaining the side wall thickness to +/- 0.002 inch over the entire length of the tube. It starts about 0.0093 inch thick, and after being drawn into shape eight times, the finished part is about 0.0083 inch thick. From there, the flange and the bottom are cut off and two holes are punched and shaped. The part is then cleaned, bead blasted, passivated, and coated. It is matte finished to keep it from reflecting light or shining in the operating room. All the tooling for this part was designed, developed, and built in house in the company's Thomaston, Connecticut facility.

"There are some obstacles to this," he continued. "You're changing the manufacturing process, and is that going to be suitable for the integrity of the device? There may be dimensional changes because you're doing it in a different fashion," he said, and that means working with the customer and proving the concept to the customer.

Three Main Stamping Techniques

On its website, Stewart EFI describes progressive die stamping as a cutting and forming process. The process uses "a 'die' that contains a series of stamping stations to perform simultaneous operations on sheet metal that has been supplied on coiled strip. The final metal work piece is developed as the strip of metal is processed through the stamping die. This transformation is performed incrementally, or progressively, by a series of stations that cut and form the material into the desired shape." (

Deep draw stamping is said to represent "the manufacturing of components in a cold formed environment through a succession of press operations from a flat, pre-cut metal blank. The various forms produced may be cylindrical with straight or tapered sidewalls, but many different approaches have been used over the years for other shapes and styles of parts." (

This tiny two-piece stamped hinge is cut, shaped, and assembled in a stamping machine from the same piece of metal. Photo courtesy of Stewart EFI.

Stewart EFI can save costly secondary operations by incorporating a number of different processes in the press during the manufacturing of parts. These processes include beading, bulging, coining, debossing, embossing, extruding, and knurling, as well as letting, reverse draws, side piercing, step draws, tapping, and threading.

The company describes its third main process, slide-form stamping, as "a metal stamping process that combines the progressive die process with additional forming stations in a self-contained specialized piece of equipment." Because the company can produce progressive die and slide-formed components, it says that its engineers and toolmakers "will design and build the tools and dies using the process that is best suited" to give customers "the highest quality part at the lowest total cost." (

"In our stamping process, we routinely work in tolerances as tight as 0.0005 of an inch on lengths, outer and inner diameters, hole sizes and wall thicknesses, on materials as thin as 0.003 of an inch, the average thickness of a human hair in a variety of metals," said Labas. "Our goal is to achieve all this while running at ever higher speeds in cost efficient mass quantities with zero defects, and our quality record is measured in ever decreasing parts per million."

Quality is Modern Manufacturing's Key

He said that years ago, job shops used to talk about "AQL," or acceptable quality level, referring to how many defective parts were allowed per thousand or 10,000, or 100,000 parts delivered. A level of 1.5 percent meant that in a batch of 100,000 parts, 1.5 percent defective (1,500) might be acceptable. If a batch had more than the AQL, the batch would be rejected. Labas said, "Now it's parts per million, and everyone wants 100 percent perfect, and we're measuring in parts per million."

One part Stewart produced in November, an EKG stud, was being stamped out at a rate of 800 strokes per minute with five studs stamped per stroke. That works out to a customer order of roughly 600 million per year. "You do the math," Labas said.

Stewart opened an 11,000-square-foot addition to its Thomaston facility in 2015, part of an approximately $6 million investment in added space and equipment that includes new stamping machines. "Much of the new equipment investment was made to allow us to make larger deep-drawn parts for our expanding customer base," said Labas in an emailed response. New ideas are evolving at a faster rate than ever before in history, Labas added, and he expects that trend to keep accelerating.

This technical information has been contributed by
Stewart EFI

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