Efficient sorting, handling, can help mine precious metal
September 16, 2008
Today's escalated metals prices have made scrap a hot issue. Multi source article covers new trends and old favorites in efficient scrap handling and in minimizing scrap
At today's elevated prices, scrap is almost considered a precious metal. In some cases, scrap is double its value only a few years ago.
Scrap metal is one of the U.S.'s largest exports and the main component in electric arc furnace (EAF) steel production; therefore, its export has become a major point of contention in steel price cost debates.
Considering today's high cost of metal and high value of metal scrap, it is more important than ever to perfect strategies to capture scrap efficiently to recover some material costs.
So how is scrap handling technology evolving to help meet this challenge? What have manufacturers done with scrap handling technology that is new?
Scrap equipment manufacturers offer an arsenal of machinery to separate, concentrate, move, detect, and recover scrap. This includes magnetic, electromagnetic, and vibratory metal sorting equipment; magnetic, underground, belted, shaker, and shuttle conveyors; automated material handling systems to transport scrap; and point-of-generation scrap reducers to minimize the space that scrap consumes at the press.
Charles Whitt, marketing manager at Bunting Magnetics, Newton, Kan., said the primary effect of scrap's high value is a dramatic increase in scrap sorting for recycling. "The issues that we get feedback on consist of mixed scrap being run together. Usually this involves the mixture of aluminum and stainless steel."
Stampers are forming a broader range of materials than in the past—high-strength steels, aluminum, stainless steel, copper, lead, tin, and zinc, Whitt said, driving the need for highly flexible equipment that can handle all material types. Because the values of steel, stainless, high-strength steel, aluminum, and copper scrap are significantly different, the need for separators that segregate one type of metal scrap from another or from nonmetallic material has become more pronounced, according to the company.
Bunting's new XTractor, to beintroduced at IMTS 2008, is specifically manufactured to streamline the separation of ferrous and nonferrous material, Whitt said. It is equipped with a self-cleaning drum separator and provides continuous separation from a range of bulk and granular materials, he said.
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An Eriez magnetic chip and part conveyor transports punch press scrap from a pit. A long, horizontal conveyor located in the pit conveys and elevates scrap to a second conveyor that transports the scrap to a hopper. Conveyors from multiple pits transfer material to a common conveyor above the pit for transport of scrap to a common hopper.
Photo courtesy of Eriez, Erie, Pa.
The company also produces cross-belt separators that continuously remove ferrous material on open conveyors. "Our 950 series separators are made for heavy-duty applications and have deep, 10-inch reachout. They will magnetically remove material from burden depths of 4 to 8 inches at belt speeds up to 300 fpm," he said. Cross-belt separators can pull material from both trough and flat-belt conveyorsand now feature a top-mounted motor that runs at a constant speed for peak separation efficiency, he added.
"By separating the stainless from mild steel from aluminum, stampers are getting a higher return on their scrap metal because it is already divided, and operators don't need to separate it," Whitt added.
Dan Zimmerman, metalworking market manager for Eriez, Erie, Pa., noted a trend toward the stamping of high-value metals. Their value makes separating them for recycling even more critical. "The separation of mixed metals can significantly increase the scrap's value. Scrap handling equipment that can separate metals can be a great advantage to the overall profitability of a project," he said.
Many types of separation equipment—such as magnetic drums, magnetic pulleys on conveyors, and magnetic grates—are used to separate ferrous from nonferrous metals. The selection of the appropriate magnetic separation equipment largely depends on the size and shape of material being processed, Zimmerman said. Choosing the right equipment also depends on the answers to the following: What is the moisture content of the material? Is oil present? How well does the material flow? according to Zimmerman.
"When it comes to machine chips, moisture content and material flow become very important," Zimmerman said. "To get good material separation, the minority material—ferrous or nonferrous—needs to be liberated from the majority material. If oil is present or chips are mixed with stringers and birds nests, the chips cannot be liberated easily." The same is true for punch press scrap, he said.
"Separation is still possible, but you may need to trade off cleaner ferrous material and carryover of ferrous into the nonferrous faction, or vice versa. Ideally, chips are small or ground, dry, and free of oil for optimal separation. This can be accomplished by incorporating choppers, wash systems, and wringers prior to separation," Zimmerman said.
Transport Odd, Large, Mixed Shapes, Sizes. "Many of our customers are dealing with scrap that is more than a foot in diameter. Without magnetic conveyors, they experience processing issues when it needs to be moved around corners, up inclines, or down declines. Asa result, many customers are ordering customized solutions to their needs," Whitt said.
"We now provide a wide range of light-, medium-, and heavy-duty magnetic conveyors through our MagSlide® product line to fit as many different applications and environments as possible," Whitt said. "Each line of conveyors has options for part shape and material thickness, belt surface type and rigidity, and conveyor position—horizontal, vertically inclined, or angled—to handle a variety of materials," he said.
For example, the company's Z-shaped conveyors allow the proper transport of odd-shaped and different-sized material without disruption of product flow, Whitt said.
Zimmerman said mixed shapes that tend to hook together can be problematic and difficult to separate. "For best separation results, scrap choppers are often installed into the process ahead of the magnetic separators."
Handle Heavy Duty. Zimmerman said press trends toward higher capacities are intensifying demands on scrap machinery. "Selecting equipment that can stand up to the demands of the job is crucial. Also, in today's metalworking applications, material must often be conveyed continuously throughout the plant. In addition, the equipment often is installed in locations that are not easily accessible. So the conveyor in use must be dependable, rugged, and relatively maintenance-free," Zimmerman said.
Eriez' Tuf-Trac™ magnetic chip and parts conveyors are engineered with the company's proprietary internal track system, designed for low maintenance, quiet operation, and long service life for moving and elevating ferrous materials such as chips, turnings, small parts, and stampings. Except for an externally mounted drive motor, the unit is self-contained, and the conveyor mechanism is completely enclosed. There are no moving external parts to jam, break, or endanger personnel, Zimmerman said.
"Eriez conveyors use a continuous series of powerful ceramic magnets that pick up and glide materials along a stainless steel slider plate. Material is then discharged over the head end," Zimmerman said.
Keep Scrap in Line. "Our customers tell us that they have concerns regarding scrap bouncing off of conveyors between parallel presses," Whitt said.
"Our equipment has evolved to incorporate neodymium magnets that have significantly higher strength to handle a wider range of shapes and weights of material being separated. These neo magnets help prevent bouncing because they snap the scrap to the profile of the conveyor. This prevents jamming to ensure positive product flow through the process," Whitt said.
Protect in Liquid. "Optional watertight housings can be submerged into almost any type of hot or cold liquid," Whitt said.
Because of their liquidtight construction, Eriez' lower conveyor sections can be completely submerged in coolant sumps or tanks, the company said. "The working face is self-cleaning, and excess fluids drain back into the tank. They are effective in stamping operations where small parts and scrap must be continuously moved from tight spaces at severe elevations up to 90 degrees and often from a liquid quench," Zimmerman said.
Halt Scrap Carryover. Stampers that have experienced jamming and safety problems caused by scrap falling into exposed areas while using hinged metal belt conveyors may be interested in improvements designed to eliminate those problems.
Ron Chapman, a director for Prab, Kalamazoo, Mich., points to a void in scrap handling quality control and said that scrap carryover has been a problem for stampers in the past. "Carryover is scrap that gets caught in the belting and upper and lower return tracks and is carried back under the conveyor. This causes jams, downtime, and premature wear. Prab's new HD Oscillating Conveyor™ eliminates this problem," he said.
"Heavy-duty, hinged steel belt conveyors are still a shop favorite," Chapman said. "Many hinged steel belt conveyor components have been re-engineered to make the conveyors more dependable and easier to service and maintain.
"For example, the 25#ASCE Rail is used on both the carry and return tracks and even in the bend sections to minimize wear. No replacement is required on the track sections. The open frame conveyor design is cleaner and easier to maintain than a closed frame."
For operations generating small slugs or lamination scrap, Prab's Pivot Belt Conveyor™ has unique overlapping hinged pan sections that strike previous sections at the discharge end, dislodging wet, oily, and sticky scrap. The scrap is then positively discharged into a scrap metal container, Chapman said.
Automate for Seamless Operation. Prab's Chapman said that ideally, scrap handling systems should be seamless to the whole operation. "The biggest challenge is to provide consistent and dependable automatic systems to make the transfer of stamping scrap a nonissue in a high-volume production facility," he said.
"Many stampers focus on obtaining new and improved, faster stamping production methods, but often neglect the 'nonproduct' side of the equation. To have a truly fine-tuned production facility, the equation needs to be balanced with a tried-and-true scrap transfer system that provides dependable, efficient, automatic handling and removal of skeletal trim, slugs, and even die lubes. Automated scrap transfer systems improve housekeeping, safety, and, ultimately, reduce labor costs," Chapman said.
"Automated systems need to be at the foundation of any new project or expansion," he added.
Today's high scrap transfer rates require faster yet more accurate trailer filling at the loadout area, Chapman said. "This is facilitated by a combination of weigh scales, shuttle distribution systems, and advanced Ethernet logic control systems," Chapman said.
Remove Scrap at Point of Generation. The majority of the scrap generated by slitters, multiblanking lines, and cut-to-length lines is the edge trim, said Ray Kuch, regional manager, Braner USA Inc., Schiller Park, Ill.
"While safety is always the No. 1 concern, our customers also want to be able to generate scrap without limiting or adversely affecting the productivity of the complete line. Then they want the ability to access the generated scrap and remove it from the machine area efficiently," Kuch said.
The company builds scrap winders, scrap ballers, and scrap choppers(see Glossary sidebar) with various capacities and methods of removing the generated scrap to meet these requirements, Kuch said.
Braner's Dual Rotor Helical Scrap Chopper is constructed of two chopper heads (one for the inboard scrap and one for the outboard scrap). Each head laterally adjusts to align with the scrap trim and has upper and lower forged steel rotors fitted with multiple helical scrap cutters arranged around the rotor periphery.
As scrap trim is generated, the trim is directed between the upper and lower rotors where the scrap is slit from edge to edge by the helical cutters as the rotors turn. Compared to ordinary "lawnmower" choppers with a single rotor and rectangular blades, the Dual Rotor Helical Chopper generates significantly less vibration and noise, Kuch said.
Because of increased global demand for metal and metal scrap, economists and industry analysts predict that the heightened demand and high value of scrap has no end in sight.
Bunting's Whitt said, "We anticipate providing a wider range of products that will sort scrap faster and more accurately. So, newer product models will need further enhancements in capacity and the variety of material they can handle."
Eriez' Zimmerman said that current technologies such as vibratory/shakers, belt conveyors, and magnetic conveyors are likely to be around for some time. "The ongoing challenge is the continuous improvement of efficiency and reliability of these technologies, as well as flexibility in their configurations and designs so they can adapt to the specific requirements of the project."
Loadout— Site where the scrap is unloaded into a container for disposal or recycling.
Scrap Baller — A machine similar to a winder, but the edge trim falls into an accumulation pit and then is gathered onto a drum and forced into a compact ball with a mashing roll.
Scrap Chopper — As scrap comes off the line, it is conveyed at line speed into a chopper that cuts the scrap into short lengths or pieces.
Scrap Winder — Machine that winds the edge trim into compact bundles onto tapered mandrels with a hydraulic-powered levelwind that moves the scrap strands back and forth across the face of the winding mandrel into evenly wound bundles.
Scrap handling machinery manufacturers agree that it is important to include scrap handling in the initial stages of press purchases, operations changes, and plant expansions.
"Often the material handling equipment for a project is an afterthought—'Let's get a conveyor in here.'" Zimmerman said. "This approach tends to be a make-do solution, rather than a best-fit-for-the-application approach."
Prab's Chapman added, "Getting us involved in the initial planning stage is beneficial and can almost guarantee a successful outcome. We identify the custome's present and future needs, and then incorporate the necessary equipment and specialized components."
"The scrap removal is addressed as part of the design, as logistical issues must be addressed," Brane's Kuch said. "Modifications to existing equipment can be the most difficult, because we have to take into consideration how the new or modified method affects the other line components."