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Engineering the Press Stroke Using Servo Technology

By: Brad Kuvin

Wednesday, August 22, 2018
 

September 25-26 in Grand Rapids, MI, we’ll hold our seventh annual Servo Technology Experience for metalformers, promising a plethora of useful technology tidbits stampers can take back to their shops, and immediately apply. When we launched the conference in 2012, the focus was directly on servo-press technology. Now we’ve turned our sights to creating an advanced servo-technology conference, Servo 2.0 if you will.

Presentations planned for Grand Rapids include experts from the automotive industry sharing their perspectives on the role servo-based equipment plays in stamping high-strength steels and aluminum alloys. And, we’ve lined up a full slate of experts covering, in great depth, how servo-based equipment brings speed and precision to the pressroom like never before.

Speed and Precision

Mark StevensServo presses move fast, forming the centerpiece of servo-technology-saturated pressrooms operating at an ever-quickening pace—a money-making pulse. Servo presses, along with their state-of-the-art support equipment, often run at two to three times the speed of conventional mechanical presses.

The challenge, then, as described by several of the speakers planned for the Servo Technology Experience, is ensuring that all of the press-line equipment work precisely in concert with speedy servo presses. This year’s keynote speaker Mark Stevens, a former GM executive and now a project manager with the Center for Automotive Research, describes the advantages of servo presses this way:

“When servo-mechanical presses splashed the industry 15 to 20 years ago, we quickly understood how the ability to engineer the press stroke would allow us to reduce initial shock, saving the press and the tooling and significantly extending the maintenance cycle. Servo technology also allowed us to minimize or even eliminate the impact of springback and twist on part dimensions when working with higher-strength materials. Then, as we took on even higher-strength materials, where you need to add heat and pressure to the workpiece during a dwell at bottom-dead-center, servo becomes a significant enabling technology.

“The ongoing transition to structural-aluminum parts in automobiles,” Stevens continues, “makes servo-press technology even more critical. I know of (and will describe during the conference) one company installing five servo-press lines to stamp high-strength aluminum frame components.”

Engineering the Entire Process

Paul StirrettWhile Stevens speaks of “engineering the press stroke,” servo-based technology allows metalformers to engineer the entire press-line operation. So notes experts from transfer-system supplier Linear Transfer and simulation-software provider T-Sim, both of whom will speak at this year’s conference.

“The pendulum-motion profile employed by most, if not all, users of servo presses offers great improvements in speed and cycle time,” says Paul Stirrett, vice president of sales at Linear Transfer, “but it gives the transfer system very little time to make its moves. That’s why equipment providers up and down the press line have been focused on moving more quickly, and with more precision. To help drive home this point, I’ll show a video during the conference of an installation we recently completed where we’re working with a pendulum-motion press application at very high speed.”

Speed from servo presses has escalated so much, Stirrett adds, that he’s noting a trend toward using linear motors in some very specialized applications.

“We are starting to see applications where press speed requires linear-motor transfers,” he says. “These higher-torque and higher-speed setups, while more expensive than servo-based machines, can prevent the material-handling function from becoming a bottleneck. These systems can pull up to 10 Gs and still precisely control part location.”

During his talk, Stirrett will describe one such system—a solar-panel production line capable of running at 120 strokes/min. Also on Stirrett’s agenda: Depiction of the latest/greatest in end-of-arm transfer tooling, and new tools designed to facilitate quick changeovers.

Curvilicous

Corey ChamberlainWhile new technology often can pay for itself in a reasonable amount of time, some metalformers strive “to make more with what they currently have,” notes Corey Chamberlain, owner of T-Sim Solutions, a developer of transfer-system simulation software.

“We’ve been seeing this trend for some time,” he says—“a big push to optimize productivity and get the most out of existing equipment.” In doing so, Chamberlain recommends that metalformers take a close look at their transfer-system motion curves. There they’ll often find at least another 15- to 20-percent gain in productivity, leveraging the mathematical power of simulation software to help optimize motion parameters such as acceleration and velocity.

“Using the software, we can examine each portion of the transfer cycle individually,” he explains, “and lock down the parameters at their maximum. This way, if there’s a problem with one axis of motion, we can slow down only that portion of the motion profile but maintain optimum speed of the other axes. In addition to discussing the power of the software to engineer transfer motion, my presentation will look at how to design for production rather than simply making a good part.”

Example: Don’t place a gauge right next to a transfer finger, Chamberlain says, which would require the transfer system to lift significantly higher to clear the gauge before indexing the part forward in the die. Instead, take care to locate gauges, pins and bushings so as to not impede transfer motion.

“In the end,” he says, “tooling designed for production allows us to ‘share time’ in the transfer cycle, so that the transfer system can index along two or three axes simultaneously, reducing overall cycle time.”

Fast Feed

Similar to the notion that the press line can only cycle as quickly as its slowest-moving part, manufacturers of feed equipment have been busy of late perfecting their wares to work in concert with the servo press. Key among improvements, according to Mike Roy, regional sales manager with feed-system supplier Formtek-Maine: feeds that are electronically geared to the press, to ensure accurate, precise feeding at the highest possible press speed.

“In pendulum mode, which we know enables very high press speeds,” Roy says, “we chop off the feed time—there’s less time to move the material. This means that we have to feed the material faster than ever, yet avoid slippage. Feed suppliers, as I’ll explain in my presentation, have, therefore, optimized the development of four-roll feed systems. These setups optimize the surface area of the feed rolls in contact with the workpiece material to ensure a good grip and precise feed with each press stroke.”

Also on Roy’s agenda: discussion of servo-based pilot lift, another speed enabler.

“This technology,” he explains, “replaces the use, in a conventional mechanical press, of a programmable limit switch or, in some cases, a proximity sensor on a cam to signal roll lift and initiate the feed.”

Servos in Action

So, where do we see applications for servo technology shining in today’s pressrooms, and in the pressroom of the future?

Many stampers have found that deep-draw and blanking processes can be dramatically improved by performing the work on a servo press instead of a conventional mechanical press. Servo Experience attendees will hear first-hand from researcher David Diaz-Infante, from the Ohio State University’s Center for Precision Forming (CPF), details of such process enhancements. Recent CPF studies focus on drawing of nonsymmetrical parts and round cups, and on cushion pulsation to improve drawability.

Another exciting and relatively recent development: use of servo presses for hot stamping, to be addressed by Scott Braito, director of sales for Seyi Presses. Seyi recently installed a servo press at the R&D center of a stamper in Japan to prove out the hot-stamping process, and currently is installing a production servo press (1200-ton, four-point) for hot stamping at a Tier One automotive stamper in Alabama.

“While hot stamping has long been relegated to hydraulic presses,” Braito explains, “metalformers have begun to understand benefits of servo-mechanical presses for this work. The presses can stop at bottom and hold the material under load (typically for 5 to 10 sec. during hot stamping) to provide heat dissipation as well as to overcome any springback issues. Then we can, due to the design of the press drive system, provide enough power to break the ram free at the bottom of the stroke and quickly complete the cycle. Since we can move the ram down and up more quickly than with a hydraulic press, cycle times can notably improve. I’ll illustrate this using the work done in Japan (noted above) and in our factory.”

Wait, There’s More

Also on the agenda:

  • Developments in Motors, Drives and Controls Impacting the Pressroom

Tim Barry, metalforming business development manager at Siemens Industry, will describe new press powertrain and control technology that makes retrofits, or even new press purchase, perfect business sense.

  • Tales from the Road—Real-World Pressroom Applications

Todd Wenzel, president of equipment distributor TCR, will describe recent installations of servo-based equipment—presses, feeds, transfer systems and more—and explain how the technology pays off with improved productivity and quality.

  • Automatic In-Die Part-Quality Monitoring and Tool Adjustment

James Barrett, president of Link Systems, will explain how in-die part measurement, die-adjustment and part-tracking technology can result not only in 100-percent verification of critical part features, but also in significantly increased machine utilization, accurate production and scrap rates, and more reliable die protection.

“The unique capabilities of servo presses enable more and better applications of this technology,” Barrett says.

The PMA/MetalForming magazine Servo Technology Experience takes place September 25-26 in Grand Rapids, MI, immediately following the PMA West Michigan Suppliers Night. Learn more and register to attend. MF

 

See also: Linear Transfer Automation Inc., T-Sim Solutions, LLC, Link Systems, Siemens Industry, Inc., TCR-Integrated Stamping Systems

Related Enterprise Zones: Presses


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