July 11, 2006
Stampers, precariously squeezed by tight margins, high material costs, and increasing pressure to be leaner, have issued a request: we want our scrap handling operations to be faster, trouble-free, and more productive. Fortunately, the latest generation of scrap handling equipment makes that mission possible. New machinery, trending toward a greater use of invisible forces and high-tech gadgetry befitting a spy thriller, is equipped with sensors, edge-guide systems, automation, and magnetic forces, equipment manufacturers say. In addition, significant improvements have been made to the scrap handling equipment itself to save space, minimize jams, and to keep it moving.
|Photo courtesy of Prab,|
Stampers, precariously squeezed by tight margins, high material costs, and increasing pressure to be leaner, have issued a request: We want our scrap handling operations to be speedy, trouble-free, and more productive. Fortunately, the latest generation of scrap handling equipment makes that mission possible.
New machinery, trending toward a greater use of invisible forces and high-tech gadgetry befitting a spy thriller, is equipped with sensors, edge-guide systems, automation, and magnetic forces and is adrenaline-rush fast, equipment manufacturers say. In addition, significant improvements have been made to the scrap handling equipment itself to save space, minimize jams, and to keep it in motion.
Push-button Automation. Interest in automating the handling of all types of scrap—heads, tails, skeletons, side trim, and slugs—is continuing to grow, scrap handling equipment manufacturers say.
"We expect that trend to continue," said Ken Shoop, Southeast regional manager, Braner USA, Schiller Park, Ill. "We'll see more automated, push-button-type scrap handling equipment to avoid manual handling of scrap as much as possible."
There are two aspects to automation—safety and efficiency, Shoop said. "I see a lot of people paying close attention to safety these days—taking a proactive approach. They're starting to realize that one lost-time injury—claims costs and so forth—is pretty expensive," Shoop said.
Efficiencies can be gained by automating the handling of scrap from coil processing, Shoop said. The head, the beginning of the coil on the outside, and the tail, the inside of the coil, usually must be discarded, he said. "Typically, you have to cut off the first and last 10 feet of a coil with a crop shear, but you can't discard the pieces at that size," Shoop said. "As you unwind the coil, you cut the scrap into 15- or 18-inch-long lengths. If you are handling that scrap manually, you have to pick the pieces up one at a time and throw them into a scrap box.
"We're seeing more and more people going to automation to deal with head and tail scrap. They're conveying it out, or a scrap cart drives out and dumps its contents into a scrap box," Shoop said.
GSW's Multiple Tray System (MTS) is especially suitable for progressive stamping. A tray is placed under each station that produces scrap, and the system is driven by one motor. Photo courtesy of GSW Press Automation, El Segundo, Calif.
Automated scrap handling eliminates inefficient, time-consuming, and sometimes dangerous practices, according to Benjamin Schwabe, general manager for GSW Press Automation Inc., El Segundo, Calif. "There are a lot of applications that produce substantial amounts of scrap, and people still do the scrap handling manually," he said. "On some, the scrap drops onto the bolster, and then the press operator has a rake and pushes or pulls the scrap out—and for that production is usually interrupted. That's when to automate," Schwabe said.
GSW offers its Multiple Tray System (MTS) that is especially suitable for progressive stamping (seeFigure 1). "If it's a multistation progressive die, there usually are several stations where scrap is produced. Now, instead of manually raking the scrap or placing an individual conveyor underneath each of those stations, we just place a tray, and instead of five or six motors, you have only one," Schwabe added.
The pneumatic motor is mounted onto the face of the bolster. A manifold with left and right linear bearing supports spans the whole length of the press bed. It is set in motion by the transporter (pneumatic motor), and then individual trays for each die station are clamped on the manifold by quick fixtures.
Eriez Magnetics, Erie, Pa., offers another type of automated scrap handling system that uses vibratory feeders to convey scrap ranging in size from small slugs to large skeletons, said Dan Zimmerman, market manager, metalworking. "These systems are composed of a metal tray supported by directional springs mounted to a rigid base. Horizontal motion is transmitted to the tray by mechanical or electromagnetic drives. Tray sizes are available in sizes from 10 feet wide to 100 feet long with multiple drive units," he said.
Sensors. Sensor systems can either shut down the press if the scrap removal system stops, or sound an alert if a material backup occurs, Schwabe said. "The sensor checks [senses] the travel of the piston of the motor and signals back to the press control. "Not monitoring the motion could result in die or press damage because of piled-up scrap," he said.
Prab Inc., Kalamazoo, Mich., manufactures various conveyors for automated stamping scrap systems—oscillating, magnetic, steel belt, Pivot Belt™, and a drag conveyor called the Scrapveyor II™—engineered to address different challenges in metal stamping operations, according to Robert Meyer, Prab's vice president of sales and marketing.
The steel belt sections of Prab's Pivot Belt™ conveyor pivot and strike previous sections at the discharge end, dislodging oily, sticky slugs. Photo courtesy of Prab Inc., Kalamazoo, Mich.
"To maintain high pressroom productivity, the scrap system needs to address two important areas," Meyer said. "The first is conveyor carryover. This occurs when irregularly shaped scrap jams up and fails to discharge. Often this scrap will be carried over into conveyor pits, which will then require expensive production shutdowns for manual pit cleanups. Without serious modifications, many standard conveyor designs cannot perform reliably in these situations. The problem can be best avoided by using conveyors that are designed for positive discharge," he said.
"Prab's deep-trough Scrapveyor II drag conveyor was specifically engineered to address carryover," Meyer said. It features a single-side chain design with a series of hinged pusher flights that engage the scrap and convey it along the length of the trough to the discharge. These units can convey material more than 400 feet and elevate it up to 45 degrees. When scrap surges occur, the hinged drag flights are designed to move through them, scalp off a portion of the pileup, and carry it further down the line. Subsequent drag flights continue to move the remaining scrap until it reaches its final destination, eliminating the need for shutdowns.
Sticky, oil-coated stamping slugs are a second challenge, Meyer noted, because the oil tends to make slugs adhere to the conveyor belt, and they can become lodged in the conveyor frame or end up on the plant floor. "The seamless, rigid steel hinges of Prab's Pivot Belt conveyor are designed to pivot sharply at discharge, expelling scrap material with minimal carryback," Meyer said (see Figure 2).
Scrap Separators. Because the values of steel, stainless, and aluminum scrap are significantly different, the need for magnetic separators that segregate one type of metal scrap from another or from nonmetallic material has become more pronounced," said Mike Wilks, director of marketing and sales, Bunting Magnetics Co., Newton, Kan. "So much scrap today is made up of many components," Wilks said. "Some of our customers have plastic and metal mixed together, especially in electronics, computers, and so forth. There's a lot of steel in computers, but there's a lot of plastic too—how do you recycle that? Those are the kinds of issues our customers are running into today that we're trying to address with separators."
How well the magnetic separators work varies, depending on the material, Wilks said. "It's very difficult to separate brass from steel, or steel from copper; it's fairly simple to keep stainless steel from carbon steel. Separating aluminum from stainless is a little trickier, and it requires more sophisticated equipment," he said. Eddy-current separators can be used to separate aluminum parts from stainless, he said, as long as the aluminum parts are larger than a quarter.
Edge-guide Systems. One way to simplify scrap handling is simply to reduce the volume of scrap that needs to be handled, thereby also minimizing scrap loss and maximizing yield, Shoop said. To meet that challenge, Braner has developed user-friendly edge-guide technology that allows coil processing lines to run with a miminal edge trim, he said.
In a coil processing line, such as a slitting line or a cut-to-length line, scrap edge trim must be cut off the sides of the coil to ensure accurate width on the outside cuts, Shoop said. "Take, for example, a slitting line. Let's say you start with a 74-inch-wide coil, and the order calls for two 36-inch-wide coils. You make a cut in the middle, and then one cut on each side, so you'll have two strips exactly 36 inches wide—a total of 72 inches—and you throw away the outside edges," he explained. "The uncoiler moves back and forth to compensate for coil oscillation and tracking issues, and so the scrap width varies from side to side. The edge-guide system controls the motion of the uncoiler to keep some scrap on both sides so that you don't lose the trim and, therefore, lose the part width tolerance on one side.
"It would make the operator's life real easy if you allowed 3 inches of scrap per side, but that's a lot to throw away, and stampers are constantly trying to reduce the amount of scrap," Shoop continued. "So let's say that you have only 1/8 inch of scrap on each side. That means the guidance system has to be perfect—there's no room for error.
"The improvements that have been made to edge-guiding technology help allow the minimal edge trim. We expect to see continued improvements in our guiding technology."
Powerful Magnetic Fields. Substantial advancements in magnetic technology during the past few years have led to the development of more powerful magnetic materials with 10 times the magnetic strength of their counterparts from a decade ago, according to Wilks. The increased strength empowers magnetic scrap handling systems to handle larger scrap, oily scrap, and to move scrap more quickly, Wilks said.
Stampers with limited room or who practice lean methods frequently want to reduce the floor space that scrap handling systems occupy, the OEMs said.
Defying Gravity. The more powerful magnets can perform gravity-defying feats that can save space as well, according to Wilks. "For example, if you're transporting large pieces of scrap and you don't have room for an angle conveyor, you can literally move them straight up a 90-degree vertical climb and then turn them 90 degrees and go straight out through the walls of the building," Wilks said. "That allows you to build a conveyor that you can drive a forklift underneath," he said.
Dorner's low-profile incline conveyor has a pulley diameter of only 3 inches, enabling stampers to get under presses even in tight areas. Photo courtesy of Dorner Mfg. Corp., Hartland, Wis.
Going Deep. Systems that collect scrap into underground tunnels and pits save considerable floor space and keep scrap and oils safely contained.
For one customer building a new stamping facility, Prab installed an in-floor scrap removal system to automatically collect, transfer, and distribute scrap into a load-out area. The scrap simply drops from the stamping presses onto an oscillating (vibratory) conveyor installed within a trench beneath the pressroom floor. This oscillating conveyor then transfers the scrap across the facility to the load-out area, where the Scrapveyor II elevates it and subsequently discharges it into a swivel-chute distribution system that evenly fills large roll-off-type scrap containers.
"Working on a new facility at the onset of a project and being involved at the design phase is the most efficient method of engineering a scrap removal system," Meyer said. "The trench and load-out area were designed, along with the pressroom, for seamless operation. Also, special care was taken to provide chuting and side skirts to prevent any material spillage at the press locations. In addition, safety devices, conveyor monitoring, and level sensors controlled by a single programmable logic controller within the system control panel added further performance guarantees."
Keeping a Low Profile. For those who can't dig a cavity under the floor, low-profile conveyors may be an option.
Dorner Mfg. Corp., Hartland, Wis., set up a low-profile conveyor system for one customer (see Figure 3). "On their presses, the scrap chute sits about a foot off the floor. What they were using previously was a shallow pan and trays, and they were collecting the trays by hand. They had no other way to get scrap from such a low point up to a higher bed," said Gary Wemmert, director of new business development.
Dorner's LPZ low-profile, Z-shape incline conveyor has a pulley diameter of only 3 in., enabling stampers to get under presses even in tight areas, Wemmert said.
"The LPZ got underneath that chute to carry the metal scrap up to a higher, larger collector bin," Wemmert said. "Our customer said they need to change that bin only twice a week, versus every hour. That's how they were able to improve their productivity."
Crashing Customs. GSW's Schwabe encourages stampers to consider alternatives to what he described as a "cultural custom" they sometimes have to gain flexibility and save space. "Many American [stamping] manufacturers cut a hole in their press bolsters or buy the presses already prepared like this to drop scrap through, and use either gooseneck conveyor systems or underground systems for its removal," Schwabe said.
Dorner's patented Wedge- Lok System protects the conveyor's end drive and pulley from damage by locking the pulley end to keep it from moving during a sharp impact. Photo courtesy of Dorner Mfg. Corp., Hartland, Wis.
"As much as this offers flexibility and potentially saves floor space, we have concerns that the press integrity is compromised because deflection and vibration are increased," Schwabe said, adding that this approach may sabotage today's demands for high press performance and highly accurate parts.
One way that stampers are maximizing utility of their capital expenditures is to use their scrap handling equipment on more than one press. GSW has developed a customized removable and mountable scrap handling system for a low-volume stamper. "We provided a movable manifold, hardware, and ideas to mount everything on a heavy aluminum plate and set it into premounted pouches on various presses," Schwabe said.
The rough environment conveyors often operate in are a concern, Wemmert said. "Because some fabricators often move their conveyors from one press to another, the conveyors tend to take more of a beating than if they were permanently in place." Conveyor components that get damaged include the spindles, because many fabricators place conveyors into blind areas of a press, Wemmert said. "Repeated slamming of a conveyor end against a blind hard surface can damage the spindle and frame and cause the conveyor belt to fall out of line."
To address this problem, Dorner engineered its 6200 series conveyors with a patented Wedge-Lok System (see Figure 4). The system protects the conveyor's end drive and pulley from damage by locking the pulley end to keep it from moving during a sharp impact.
In fact, some of the most significant improvements to boost scrap handling productivity are those that simply protect the equipment to keep it moving. After all, the enemy is downtime, and machine failure is not an option. The latest generation of scrap handling equipment is more durable, so it needs less frequent maintenance, equipment manufacturers say.
Bunting's Heavy-Duty MagSlide beltless magnetic conveyor removes and transports abrasive, jagged scrap using moving magnets—hidden beneath a stainless steel slider bed. Photo courtesy of Bunting Magnetics Co., Newton, Kan.
Sharp Edges. This year Bunting introduced a heavy-duty version of its beltless conveyor system to handle sharp edges of scrap that can puncture and slice belts or get caught in the hinges of steel hinge belt conveyors, Wilks said (see Figure 5). "The Heavy-Duty MagSlide® chip and parts conveyor removes and transports sharp, abrasive parts that could otherwise damage, jam, or even shut down conventional belt conveyors and hinge belt conveyors," he said. Instead of a moving belt to carry cargo, the Heavy-Duty MagSlide uses moving magnets—hidden beneath a stainless steel slider bed—to move ferrous materials along the conveyor's heavy-gauge surface. The conveyor was specifically designed to move heavy loads, Wilks said.
Twin-roller drive chains, which hold and move the conveyor magnets, travel in oiled Bunting SlideTrack™ channels that are made from ultrahigh-molecular-weight (UHMW) polyethylene. These channels provide constant lubrication to help minimize friction, chain wear, and noise. Built-in oil fittings allow for manual or automatic supplemental lubrication to extend chain life even more, Wilks said.
Other scrap handling equipment manufacturers have looked to their lubrication systems to make improvements as well. "While magnetic conveyors and vibratory feeders have been around for a long time, we are continuously improving designs to ensure optimal operating performance while minimizing maintenance requirements," said Zimmerman. Eriez' Tuf-Trac™ is equipped with an oil-impregnated UHMW polyethylene track designed to eliminate the need for oil within the conveyor housing, as well as to operate quietly and maximize conveyor life, he said.
"Safety and maintenance requirements are always a major concern and challenge for metal fabricators handling scrap," said Zimmerman.
"Hinged metal belt conveyors and other types of belt conveyors tend to require higher maintenance and can present safety issues with the frequency of having to maintain equipment and unjam parts and scrap from the conveyor." Eriez offers magnetic conveyors or vibratory feeders as alternatives, he said.
Eriez' magnetic chip and parts conveyors provide an almost maintenance-free way to move and elevate ferrous scrap, Zimmerman said. "Except for an externally mounted drive motor, the unit is self-contained, and the conveyor mechanism is completely enclosed, so there are no moving external parts to jam, break, or endanger personnel," he said.
Loose metal slugs have always been a concern to fabricating customers and their conveyors, Dorner's Wemmert said. "That's because slugs are small, sharp, and hard to contain. If slugs work their way underneath the conveyor belt, it can cause major damage to not only the conveyor belt, but also to the bedplate and spindles," Wemmert said. "In some applications a urethane belt, which is susceptible to rips and tears from metal slugs, can be replaced with a plastic chain belt, which is not only cut-resistant, but also resistant to high temperatures and chemicals."
Scrap equipment manufacturers concurred that using the right equipment for the application is critical to achieving optimal performance and reducing problems.
Improvements in the productivity of metal fabricating equipment and the associated capital costs make it even more important to properly apply the most efficient and reliable material handling equipment to support fabricating operations, Eriez' Zimmerman said. "Having a production line down due to problems with auxiliary equipment can be detrimental to the profitability and viability of metal fabricating operations," he added.
It's important to use a conveyor that is built for the environment it will be in, Wemmert said. "If you have a conveyor, for example, that has open bearings in a harsh fabricating environment with lubrication and other fluids being splashed around, it's going to fail that much faster," Wemmert said, adding that the most suitable equipment may cost more initially but save time in the long run.
"When you cut off the coil edges, you can't just let the scrap go—well, actually, I did once see some people just run it off on the floor and run for their lives," Shoop said. The trimmed edges should be wound up on a winder or chopped up into small pieces. Braner has expanded its side trim scrap machinery to include scrap winders, scrap balers, and scrap choppers to match the most appropriate equipment with the type of material processed, he said.
"We often receive calls from customers who purchased a scrap handling system, only to learn later that it wasn't the best system for their application," Wilks said. Bunting's field salespeople analyze applications, discuss them with their engineering staff, and make scrap handling system recommendations, he said.
Braner USA Inc., 9301 W. Bernice St., Schiller Park, IL 60176, 847-671-6210, fax 847-671-0537, firstname.lastname@example.org, www.braner.com
Bunting Magnetics Co., 500 S. Spencer Ave., P.O. Box 468, Newton, KS 67114-0468, 800-835-2526, fax 316-283-4975, email@example.com,www.bunting magnetics.com
Dorner Mfg. Corp., 975 Cottonwood Ave., Hartland, WI 53029, 800-397-8664, fax 800-369-2440, www.dorner.com
Eriez Magnetics, 2200 Asbury Road, Erie, PA 16506, 814-835-6000, fax 814-838-4960, firstname.lastname@example.org, www.eriez.com
GSW Press Automation Inc., 353 Coral Circle, El Segundo, CA 90245, 310-726-9620, email@example.com, www.gswpress.com
Prab Inc., 5944 E. Kilgore, P.O. Box 2121, Kalamazoo, MI 49003, 269-382-8200, fax 269-349-2477, firstname.lastname@example.org, www.prab.com
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