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Wireless I/O Stamps Out Downtime on Auto Press
Gestamp Automoción now saves up to $174,000 annually after replacing its automotive stamping press line's hardwired system.
By Adrienne Lutovsky, ProSoft Technology
At the Gestamp Automoción plant in McCalla, Ala., everything is oversized. The vast concrete floor is bare except for two giant 2,000-metric-ton transfer presses. The ceilings are built high to accommodate these beasts, making the lights above appear dimmer. Nothing can be heard above the overwhelming roar of the ram as it slams into metal sheets, molding the shape of what will soon be structural parts. Hiss, ka-JUNK, hiss, ka-JUNK, hiss, ka-JUNK.
Then…silence.
"Alright everyone, call your wives and tell them you're going to be late tonight. By the time we get these presses up-and-running again we're all going to have to work late just to meet production requirements," Mike Mullins, the press maintenance team leader, breaks the news to his crew. "This is going to cost us."
And this isn't the first time. Gestamp Automoción owns and operates more than 70 transfer presses and 100 progressive presses, but the two transfer presses at its McCalla facility had been causing a ruckus. At least once a quarter, the hardwired network suffered cable degradation, and each occurrence caused the entire operation to shut down for up to two hours. Something had to be done.
Network Problems Take Down the Plant
Gestamp Automoción is a tier one, Spanish-based automotive supplier with 56 production centers in 17 countries. They produce metal components for most of the leading automobile manufacturers, including Mercedes-Benz, Porsche, Bentley, BMW, Ford, GM, Nissan and Suzuki.
At the McCalla facility, much of the production is for the Mercedes-Benz plant in Tuscaloosa, Ala. The plant uses two presses that produce up to 1,800 parts per hour. The presses were hardwired and faced frequent downtime from cable breakage or damage, frustrating the plant-floor team.
Figure 1: This is the front of the stamping press bolster where operators load the dies.
"The RG-6 coaxial cable we were using cost $57 per foot, and we had about 165 feet to replace each time the system went down," Mullins explains. "The cable alone cost between $9,400 and $9,500 to replace, and that's not including the cost of the system shutdown. We once estimated the overhead costs of downtime at about $2,500 an hour, and it typically took a couple of hours to replace the cable."
It cost Gestamp about $14,500 each time they had to replace the cable, plus the value of the 1,500-2,400 parts that could not be produced during the outage.
"It wasn't uncommon for this cycle to repeat every 2 to 3 months per press," Mullins says.
The application involves two presses. Each press consists of one ram, two dies and two bolsters. The bolsters are mobile metal plates on which the dies are mounted (see Figure 1). A die is used as a mold that defines the shape that the part will take. In this application, each die is roughly the size of a one-ton pick-up truck.
During the process, a metal sheet is fed across one bolster and comes to a rest above the dies. The ram rises and drops with a force of 800 to 1,400 metric tons, sandwiching the metal sheet between itself and the die to stamp out the parts. While one of the bolster stamps parts, the second is loaded.
System Demands Were Core to the Problem
Figure 2: Before implementing the wireless network, the hardwired cable’s path ran along a corner with such a sharp angle that it suffered cable degradation.
The cable wasn't as much the problem as the demands placed on it. The cable's path ran along a corner that required such a sharp angle that it inevitably wore in this area (see Figure 2).
Nevertheless, Gestamp needed a more reliable network. However, managers wondered whether a wireless system would be effective given that wireless points would need to be affixed in a partially obstructed location beneath the bolsters.
"What we really needed was a radio that could communicate through a ten inch thick plate of steel," Mullins notes.
Line-of-Sight is No Problem
Since he would be hard-pressed to find a radio that can penetrate steel, Mullins spoke with his local Rockwell Automation distributor, who recommended using six Frequency Hopping Ethernet radios (RLX-FHE) from ProSoft Technology®, a participating EncompassTM Product Partner in the Rockwell Automation PartnerNetworkTM, with Gestamp's existing Allen-Bradley® ControlLogix® programmable automation controllers (PAC).
Kevin Zamzow, ProSoft Technology's strategic product manager for Wireless Technologies, explains, "When the direct path [line-of-sight] is obstructed, a signal will reflect off of other objects, taking an alternate path to the receiving radio. Because there are multiple reflections, the signals arrive at the receiving radio at different times, so the radio needs to be able to distinguish between the different signals."
"ProSoft Technology's Frequency Hopping Spread Spectrum [FHSS] radios can work with reflected signals because of the narrow band ‘hops' and changing frequencies, making them less impacted by multipath interference compared to higher-speed, wider-band technologies such as 802.11," he adds.
Wireless Network Replaces Hardwired System
Figure 3: The ControlNet communication adapters on each of the four bolsters were replaced with EtherNet/IP adapters and an Ethernet radio, as shown here around one of the 10-inch-thick steel plate bolsters (painted black and yellow).
Each press is automated by a dedicated ControlLogix PAC. To replace the hardwired system, four ControlNet communication adapters — one for each bolster — were replaced with EtherNet/IP adapters and an Ethernet radio (see Figure 3). Each PAC was fitted with a second 1756-ENBT Ethernet card and an Ethernet radio.
Cliff Whitehead, manager of strategic applications for Rockwell Automation, notes, "EtherNet/IP was designed as a media independent solution, and Gestamp has been able to directly take advantage of this flexibility in their wireless application."
"One of the key advantages of Ethernet-based automation networks is the wide variety of solutions for wireless Ethernet bridging," adds Harry Forbes of the ARC Advisory Group. "These solutions can have enormous value in manufacturing applications."
Uninterrupted Performance Cuts Costs
Gestamp has eliminated the downtime plaguing its McCalla facility, translating into a savings of up to $174,000 per year, plus the value of parts produced during that time.
"We've got a unique application here, involving large moving hunks of steel. Our initial concerns that the steel would impede the radio performance turned out to be unfounded. When the bolsters interfere with line-of-sight, the radios continuously try to read through the bolsters," Mullins says.
This application shows that although the laws of physics can't be changed, the obstacles they present can be circumvented when armed with the right technology — in this case, an industrial wireless solution. The wireless system has been live for two years now, and Mullins is still pleased with the performance of the radios. "In fact, the radios work better than expected. We've been very happy with them."
For more information about the products used in this application, visit www.prosoft-technology.com/wireless.