By: Brad Kuvin, Metal Forming Magazine
A tour of the stamping-press booths at last November’s FABTECH show reveals a remarkable revolution underway: Press builders are supplying modern-day press controls that provide revealing, data-packed looks at the entire press line. They’re armed with full-color graphical displays that provide snapshots of the entire operation as well as trending data to provide prediction capabilities.
On the pressroom floor, process visualization now intimately connects press operators to their machines. This connectivity and visualization provides up-to-the-second real-time information—press data such as tonnage, stroke position and die-protection data, as well as parameters related to feed- and transfer-systems, and other automation equipment.
A look around the FABTECH show floor revealed entirely new and breathtaking press-line human-machine interfaces (HMIs) that promise to help operators translate complex data into understandable information. In this new era of having process data delivered and digested at the plant floor, foremen and perhaps even operators can make on-the-spot decisions and adjustments that can make a real impact on the bottom line.
…is the word I keep hearing when I talk to controls experts and press manufacturers showcasing new controls at FABTECH. When used to describe controls technology, intuitive means giving operators the ability to quickly and easily understand what’s going on at the press, and at all of its supporting equipment, with minimal reasoning required.
“We’re customizing Allen Bradley programmable-logic controllers (PLCs) and HMIs with screens that convey all of the data, in easily digestible formats, that operators and supervisors can quickly and easily learn to use,” says Mark Sutherland, president of Sutherland Presses Inc. “Intuitive prompts (on Sutherland’s I-Press controls) are resulting in faster setups, improved overall equipment effectiveness (OEE), and more timely troubleshooting.”
Asked to pinpoint the most sellable feature of newer press controls, Sutherland insists, “it’s their intuitiveness and fully multilingual displays, critical capabilities in today’s market.”
At FABTECH, Sutherland introduced its new I-Press AB Plus control, kicking its I-Press control, introduced in 2011, up a notch. While the standard I-Press, says Sutherland, introduced a 7-in. color screen, two die-protection circuits and the ability to manage completely automated operations to avoid the need for third-party controls, the AB Plus model (with all Allen Bradley hardware and software) makes it the company’s most flexible control to date.
"The freedom of using the Allen Bradley architecture,” he says, “offers the ultimate in scalability. It lets customers grow in any direction they want—extra die protection or tonnage monitoring, for example. We program all of these ‘feature sets’ into every AB Plus model, and password-protect them. Then, if a customer wants to add the feature sets later, we only have to give them the passwords to the particular features they want.”
Safety PLCs All the Rage
Next up for the I-Press, shares Sutherland, is integrated safety using a safety PLC rather than the traditional cross-wired two-processor (primary and redundant) architecture. This move was echoed by others displaying new press controls at FABTECH.
“Safety PLCs in press controls are coming,” says Mark Heitbrink, electrical engineering manager at Nidec Minster. The firm showcased its new servo-press controls at FABTECH alongside its new servo-mechanical press. Such PLCs, with redundant and self-checking processors, provide I/O and communications capabilities so that, without having to use independent safety relays, any hardware or software failure will not “knock out” the entire control system. There’s less hardware required, less wiring, and less panel space needed.
“We already use safety PLCs in our servo-press control,” says Heitbrink, “as a necessity since the Siemens drive system on the servo presses employs a safety PLC. The safety PLC is required in the press control in order to communicate with the drive control and meet the safety standards.”
Among relatively newer control features being offered to stampers, Heitbrink points to Ethernet connectivity, built-in VPN (virtual private network) communication and, as Sutherland notes, control of overall system elements including conveyors and die clamping.
A Lot More to Discuss Related to Servo Press Controls
But, Heitbrink adds, there’s a lot more to talk about when it comes to servo-press control. “We’re offering stampers the ability to customize motion profiles,” he says, “compared to controls that only allow for out-of-the-box motion profiles. We have customers, for example, using the press control to develop custom force-motion profiles for unique coining, double-hit and pendulum-motion applications.”
Servo-press controls also took center stage at the Komatsu booth at FABTECH, where company vice president Jim Landowski told me:
“We always had die-height control using linear scales to feedback actual slide-face to bolster-top position. This allowed the press control to make real-time adjustments to hold die height to within 20 microns of the programmed setting. Now we’ve added tonnage control. Using the strain-gauge output, we can maintain tonnage to within percent of the programmed setting, by having the press control direct on-the-fly slide adjustments to raise or lower the die height.”
What’s next? “We’re developing the ability to make these die-height or die-cushion adjustments based on variations in material thickness or hardness,” Landowski shares. “We expect that the stamper will be able to set up equipment to measure such variables before the material enters the die. For tandem lines, the press control will oversee the required changes in shut height at each of the presses as the part transfers down the line.”
The 19-in. Touchscreen
…at the Aida booth received plenty of attention at FABTECH. The display belongs to the firm’s new DSF-series control, and was shown at the helm of a complete servo-press line developed for metal stamper Ultraform Industries. Allen Bradley Logix-based, the control offers several new features. One of them, according to Aida America product manager Shrinivas Patil: the use of virtual-angle signals to initiate transfer-system motion.
“We manipulate the motion-profile curve,” Patil says, “and condition it so that the transfer system can follow the press regardless of the servo-motion profile selected. This is accomplished using Aida’s proprietary software that eliminates the need for complex calculations when running transfer dies using non-uniform motion profiles. It dramatically reduces transfer-setup times and shortens the learning curve.”
Patil also echoes what others say regarding HMI-design optimization and intuitive processes. “For example, we’ve integrated tonnage monitoring onto the main display screen,” he says. “Before, the operator had to toggle the main press screen to view the tonnage-monitor curves. Now it’s all on one screen.”
Patil notes a couple of additional new features to the Aida servo-press control designed to make operators’ lives simpler: three-speed step-feed control, and “smart” soft stops.
“One of the most time-consuming and challenging tasks out on the shop floor are setup and fine-tuning of new dies,” he shares. “Specifically to help with this task, with the new control we now offer a choice of three fixed speeds when the press is in the step-feed mode.”
Using the step-feed control mode, operators can select slow, medium or fast ram speed during the initial runs of a new die, or during troubleshooting, depending on where they are in the press stroke. They might, for example, run faster at the top of the stroke and then use the slowest speed when the ram approaches the workpiece, to get a close look at angles and positions. And, should something unexpected happen, the slower you’re running the less the damage will be.
“It’s much safer, too” says Patil. “This feature allows users to prove-out new dies quickly and efficiently while minimizing the risk of accidents and die damage.”
The soft-stop feature on Aida’s new servo control is designed to prevent unnecessary nuisance press shutdowns in the event of delayed signals from sensors. “In the old mechanical world,” says Patil, “the sensor signal is either there or it isn’t. And if it isn’t, the press shuts down and the operator has to go through what often is a time-consuming restart process. Maybe the lack of a signal from the sensor indicated a real issue, but maybe the signal was merely delayed by milliseconds and the press really did not need to be completely shut off.”
Now, with the soft-start feature, if a sensor signal is lagging, rather than shut off the press the control will pause the slide at a safe position and wait for a delayed signal from the sensor. Using a preset delay period allows for the action being sensed to either occur, so the press can continue, or, if the signal doesn’t eventually come, shut off the press in a hard e-stop.
The productivity benefits of such process control can be significant, Patil notes. For starters, an operator forced to troubleshoot and restart presses due to nuisance stops—let’s say delayed scrap or part ejection, for example—may not be able to tend to more than one press.
“Or, Patil adds, “consider a press and feed setup capable of running a die at 60 strokes/min. that is forced to run at 55 strokes/min. because the feed might be lagging a fraction of a second —at the higher speed, that lag time can trigger a shutdown every few minutes. Now, with the soft-start feature, the stamper can run at top speed and if the sensor signals a feed lag, the press will just stop momentarily until the feed catches up.”
Connectivity Enhances Training and Troubleshooting
Finally, as Sutherland noted, Ethernet and VPN connectivity create a clear path to improved troubleshooting. “As long as the customer connects the control to its network, we can log in and help diagnose anything that might be happening with the overall line,” Patil explains. “Often, by the time a service-tech arrives onsite he can have a report from us telling him what to look for, and in what order he should perform certain diagnostic checks. Ethernet connectivity also lets us conduct remote training. We can communicate with the operator right on the shop floor as he seeks to fine-tune a program, for example. This saves valuable time during setup and helps improve OEE.” MF