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Cr-Si Springs Produce Productivity Bounce

By: Brad Kuvin

Tuesday, January 01, 2008
 
Here’s the live-action view of the production environment at one of Oberg Industries’ stamping facilities: Upgrade a reel-to-reel die to produce terminals two-out at more than 1200 strokes/ min., yielding a 500-percent increase in production volume without any incremental increase in labor or press time.
Drawers filled with replacement die springs
Drawers in the Oberg toolroom have been filled with replacement die springs, including longer-lasting chrome-silicon springs.

That’s just one recent project of many that describes the precision stamper’s ability to step up to the plate when customers seek continuous improvements in productivity. At the same time, quality requirements intensify with each passing day. That is the reality of the production stamping business at Oberg, a $130 million company with 800 employees and stamping operations in Pennsylvania, Arizona and Mexico. Customers of Oberg’s stamping business—companies in the automotive, consumer, aerospace/ defense and medical markets—increasingly want burr-free stampings with tighter dimensional tolerances. We’re talking true-position tolerances hole-to-hole as tight as -0.00 and +0.004 in.

“To satisfy increased demands on quality and still improve throughput, we changed the way we build our dies,” says Bill Wallace, Oberg’s die maintenance supervisor. “We use new design technology standards and have developed a new system for die construction.”

In addition to taking action to improve quality and throughput, Wallace set higher goals for die life between preventive maintenance (PM). “A few years ago, if we got 4 million hits between PM cycles, that was great,” he says. “Today, I don’t accept anything less than two and a half to three times as many hits before a die requires PM. This lets us extend our service times and our run times as we continue to raise the bar on what we expect to acheive from our die designs. The dies are in the presses longer, producing quality parts, and not on the bench as often. Everyone wins.”

Die Springs Were a Weak Link

The Oberg stamping facility in Sarver, PA, down the road from its headquarters in Freeport, PA, houses 24 press lines, from 30 to 300 tons. In the last year, it’s added six new presses, and completed a 50,000-sq.-ft. expansion, doubling its pressroom size. “Our customers are buying the stampings and assemblies we’re producing as quickly as we can make them,” Wallace says. To ensure that the company continues to meet customer expectations for on-time delivery of quality parts, Wallace, with the help of Oberg’s Technology Advancement Program (a team committed to developing continuous-improvement projects), recognized that a weak link in production dies was the die springs being used.

“For example, we had one die that had been in production for more than 12 years, a real bread-and-butter job for us, that would run 100,000 hits and we’d find seven or eight broken springs in the tool,” Wallace recalls. “Springs breaking mid-run would lead to lazy forms. To get that tool where we needed it to be, we upgraded to chrome- silicon springs (SuperSprings from Ready Technology, Inc., Dayton, OH) and we immediately were able to run the tool for more than 8 million hits over a two-year span without requiring any PM. In springs alone, we saved $2500 in replacement costs. Plus the added uptime in the press and avoiding the need to have a toolmaker working on the die on the bench.”

SuperSprings, according to Ready, are formed from trapezoidal-cross-section wire, which changes to a “D” shape during the coiling process. This shape, says Ready, minimizes stress and contributes the springs’ long life.

The Root Cause: Excess Stripper Travel

“What was most damaging to the springs on this particular tool,” Wallace continues, “was the extreme amount of stripper travel we had—more than ½ in. Add that to the 3⁄16-in. preload on the spring and we simply were overstressing the springs as they were designed. The Ready SuperSprings can better handle that amount of deflection, and we’ve proved that time and time again in a variety of tools.”

Oberg specializes in stamping motor laminations, from dies such as this
Oberg specializes in stamping motor laminations, from dies such as this. Its dies, which can require 10 or more springs, are expected to make millions of hits between PM. An upgrade to the chrome-silicon springs shown here allows the firm to meet those expectations.
As Wallace and his colleagues at Oberg headquarters responsible for die specifications began to see the benefits of upgrading to Cr-Si die springs, the company initially targeted forupgrade all of its dies that experienced excessive stripper travel. Then it turned to form dies where the tools were forming on spring pressure, and then to dies where springs performed particularly challenging tasks.

“One of our dies that stamps terminals for spark-plug wires,” says Wallace, “employs die springs to insert a clip ring onto the part. We were getting 100,000 hits out of a set of springs. With the SuperSprings, we have increased the number of hits by 20 percent or more before replacing the springs.”

Longer-lasting springs also allow Oberg to improve the productivity of its press operators, who no longer need to hover over each job to make sure a spring hasn’t broken, causing part defects such as lazy forms, missing features or missing inserted hardware. Instead, operators can focus on exchanging parts bins, a task growing in importance as the firm looks to engineer more of its dies to make multiple parts per hit—five- and seven-out dies run nonstop in the plant. And, in many cases operators can more easily tend to multiple presses—two or three—at a time.

Less PM, More Productivity Enables Pain-Free Growth

“Longer, better running tools allow us to grow our business by increasing our press utilization, operator efficiency and production capacity,” Wallace says. “That will enable us to expand, without significant growing pains, from running about 300 different dies regularly to nearly 400, as we work to absorb larger transfer stamping projects. We’ll begin that work once we upgrade all of those dies to get them back to print, by changing out all of the guide components and cut edges. And, replacing all of the die springs with SuperSprings.” MF

 

See also: Ready Technology, Inc.

Related Enterprise Zones: Tool & Die


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