September/October 2003
From stripping to chopping, wire processing machinery helps recover the metals that power our electrical age. But questions about the industry’s future also challenge its technology.
By Robert L. Reid
Our electricity-driven, electronics-oriented lives demand all kinds of cables and wires to provide power to our homes, businesses, and transportation; to connect our telephones, computers, and other communication products; and to operate just about every tool, toy, and contraption that makes the modern world more convenient.
All those cables and wires, of course, eventually reach the end of their useful lives and need to be recycled for their copper, aluminum, steel, and plastic contents. That’s where wire processing equipment comes in.
From the simplest stand-alone wire strippers to complete systems that shred, chop, and separate the various nonferrous, ferrous, and nonmetallic fractions, wire processing equipment is a vital part of keeping reusable material out of landfills. This overview examines the types of equipment available and how they fit into their industry’s currently volatile marketplace.
Industry Obstacles
It’s difficult to discuss wire processing technology without first mentioning some realities of the modern scrap wire industry. Like other segments of recycling, wire processing is undergoing great changes because of China’s demand for scrap. Indeed, so much wire that used to be stripped and/or chopped in the United States is now simply being exported unprocessed that some recyclers question how long the domestic wire processing industry can survive. It’s an industry “under duress,” says one equipment manufacturer, who—like others in his field—concedes that there’s little incentive today for his firm to invest in R&D on new wire processing machinery.
At the same time, the overall slow economy in the United States is encouraging more and more cable and wire manufacturers to reduce their waste-related costs as much as possible—in some cases by installing their own equipment and bypassing at least some of the services traditionally provided by wire processors, the manufacturer notes.
In such an environment, wire processors must make smart decisions on many issues, including how they buy their cable and wire, what equipment they purchase when they want to expand or upgrade their operations, and how they run and maintain that machinery once they’ve got it. As another industry observer stresses: “You can’t afford to be inefficient anymore.”
The Stripping Solution
A key question for wire strippers involves when to strip and when to ship—that is, when to handle the cable or wire in-house and when to send it to a wire chopper? Likewise, if your operation both strips and chops, the issue becomes when to do which?
Strippers handle cable and wire in ranges of sizes from, say, material with an outside diameter (OD) of 1/4 inch to 2-1/2 inches or 1/2 inch to 6 inches, and so on. “When you talk to a customer, the very first question you’re going to ask is what’s the largest OD cable you want to process and what’s the smallest?” says one manufacturer of stripping equipment. “They’ll give you the range, and that’ll throw them into one of the particular models that all the manufacturers have.”
Generally, the smaller-sized cables and wires—those with an OD of 2 inches or smaller—can be chopped more efficiently than stripped, while material 3 to 6 inches in diameter is more effectively stripped, this manufacturer notes. He also recommends stripping wires based on their copper content, with the higher-copper wires stripped and the lower-copper wires chopped.
“You’ll get the same recovery out of the wire chopper or stripper from, say, 4-inch cable,” he explains, but such material will produce less wear on the stripper and thus reduce your maintenance costs compared with chopping the cable.
Another manufacturer recommends stripping No. 6 and larger copper wires and chopping anything smaller. Pro-duction rates can double with every two wire sizes, he adds, so that the same machine that strips roughly 1,000 pounds an hour of No. 6 will process more than 2,500 pounds an hour of No. 2 but far less of No. 14 (certain wire sizes are designated in reverse order, with the smaller numbers actually representing larger-diameter material).
In addition, some material might be partially stripped first, then chopped. Telephone cable, for instance, can have 800 thin metal conductors within an outer jacket made from a recyclable soft lead. Some stripping operations simply remove this lead covering and ship the thinner conductors to a wire chopper. Indeed, one of the perceived benefits of stripping over chopping is the ability of strippers to recover more of the insulation from cables and wires—whether lead or plastic—without the metal contamination often found in residual chopped material. Another benefit is the clean, solid wire produced by stripping, a manufacturer explains.
Other factors in deciding whether to strip or ship include labor costs, maintenance, energy consumption, how many different sizes of cable and wire the user intends to process, and how much the user wants to initially spend on equipment.
For instance, stripping equipment is available with or without a self-feeding feature that pulls the cable through the machine. Those without this self-feeding option are less expensive, one manufacturer explains, but they also require an employee to keep pushing the wire into the machine. And when stripping larger sizes of cables, one employee must push the cable in at the front-end while another helps pull it through the other end.
Likewise, some stripping equipment has a single opening that needs to be adjusted for specific sizes of cable or wire processed, while others have multiple openings to handle different ranges of sizes without having to make as many adjustments. Moreover, certain strippers feature a spring-based “floating action” that self-adjusts to handle different sizes of wire as well as difficult items—such as underground cables that get flattened when sheared and thus become harder to feed in, as well as cables with conductors that are both oddly shaped and wrapped in a hard-to-cut oily paper.
The blades in stripping equipment cut the insulation around cable and wire at points along an imaginary clock. One manufacturer, for instance, notes that the blades on one machine cut at 12:00 and 6:00. Depending on where and how efficiently these cuts are made, the insulation might drop off easily or require additional handwork to physically liberate the metal conductor, the manufacturer notes.
Another high-end option in stripping technology involves a machine that features four blades arranged to simultaneously cut the insulation away in four places, “peeling it like a banana,” the manufacturer explains. Likewise, another equipment maker offers a machine that cuts deeper than other machines to handle material such as high-voltage cable that’s surrounded by thicker insulation. The manufacturer also makes slower-speed machines that cut through the steel armoring around certain cables.
Overall, stripping equipment is a basic tool for any scrap yard handling nonferrous material—“like a screw driver or pliers in your toolbox,” explains one equipment producer. The number of strippers a yard needs is based on its production needs, with smaller facilities requiring only one machine and larger processors possibly needing six or more.
Strippers can be driven by gears, belts, or a direct drive, with at least one belt-driven machine reaching speeds of 200 feet a minute. Though some users perceive gear-driven strippers as high in maintenance, a manufacturer of such machines disputes that charge. “Make sure the stripper is full of grease, and you’ll never have any problem with it,” he says. Indeed, strippers in general have a reputation as such hardy workhorses that another manufacturer says his own used equipment is often his greatest competition.
Changes in Chopping
Though wire stripping can be done with individual, stand-alone pieces of equipment, wire chopping tends to follow a systems approach, with a series of machines performing different tasks, from preprocessing the wire to granulating it, and separating out the various components.
A basic system these days begins with a prechopper, which reduces the often unwieldy bundles of scrap wire into smaller segments—from a few inches to less than an inch in length. This step is followed by magnetic separation when there’s ferrous material to remove, then one or two stages of rotary granulation. Plastic and metal are then segregated by various means, ranging from air/density units to gravity separators to water tables.
Screening is another critical element, manufacturers note, along with additional magnetic separation at different points in the system. Automatic feeding systems, shaker conveyors, surge bins or hoppers, and aspiration exhaust systems for dust control are other recommended features.
Slow-speed, high-torque chopping is an increasingly popular approach, various manufacturers note. As one explains: “Traditionally, people used granulators to rip everything down at high speeds, high horsepower, higher rpms.” But when granulators run too fast, especially when chopping copper wire, too much metal gets lost. “Now our technology is based on ‘speed kills,’” the manufacturer jokes. “So we slow all our processors down to much lower rates, and we actually increase throughput and decrease the amount of loss” in things like fines or dust.
Specialty equipment in wire chopping includes granulators designed to handle tough material such as ACSR (which stands for aluminum conductor steel reinforced cable). ACSR often comes to processors on a giant reel that the supplier might want returned. So one manufacturer developed a machine that allows processors to simply stick the reel on a “despooler” and insert the end of the ACSR cable into a feed funnel. The self-feeding chopper grabs the cable and pulls it in at a high rate of speed, cutting up the material into whatever sized pieces are desired. As the manufacturer describes, the unit “sucks in the cable like a piece of pasta,” cuts it up, and drops the pieces onto a shaker conveyor. Magnets then pull out the steel while the clean aluminum pieces go into a box.
Another manufacturer offers a system to process jelly-filled underground cables that today are often simply shipped to China. The system features rotary water filters to wash away the insulating jelly after granulation, producing “No. 1 copper granulate with no stickiness to the surface—you can’t tell that it came from jelly-filled cables,” explains the system’s distributor.
Many processors use wet separation or electrostatic separation to retrieve the last bits of metal that might otherwise end up in their waste streams. At least one manufacturer, though, designs its chopping equipment with blades that are intended to last longer and be easily regapped, a procedure that reportedly increases the material captured during the density-separation stage and eliminates the need for ancillary recovery systems.
Though many complete wire processing systems require large amounts of floor space to house all the machinery, at least one manufacturer has designed smaller, more compact versions of its technology. These turnkey systems don’t involve as much installation, don’t take up as much space, and cost less than larger systems, the manufacturer explains, in part because they’re centered on a single granulator and separator, with expansion possible as the processor’s business grows. These units are aimed primarily at smaller processors who handle wire but whose market might not justify starting off with the most advanced systems. One such system is designed to fit in just a 30-by-60-foot building, with a capacity of 2,000 pounds an hour on most insulated copper wire and cable.
For those seeking an even more compact approach, one firm offers a stand-alone granulator that can process roughly 300 pounds of copper wire an hour in OD sizes up to 2 inches, while taking up only 10 square feet of floor space. This compact granulator weighs slightly more than 2,000 pounds, making it transportable around a scrap facility, and requires only a single operator to run.
Lessons to Learn
In both wire stripping and wire chopping, the equipment itself is only part of the equation for getting good production. As one industry observer notes, good wire chopping “does have some artistry to it as well as the basic science.”
Choosing the right wire for stripping or chopping is important, manufacturers reiterate, as is trying to run similar wire in batches to save time and effort adjusting the equipment to handle different sizes or materials.
Operator training and skill is especially critical. In discussing his own equipment, one manufacturer stresses that it takes time to learn to operate the system well. The operator can’t just “flip the switch and on it goes,” he notes. Another explains that the quality of separation from a gravity table depends on the ongoing adjustments that the operator makes to the table during processing.
Proper maintenance—especially knife maintenance—is also vital. Operators should learn to recognize the signs of when their blades need adjusting—such as greater vibration, louder sounds during operation, and material that comes out of the machine warmer than usual, one firm explains.
Regapping the blades—which involves keeping a close distance between the rotor and the bed blades—is essential to maintaining blade life and performance, and should be performed often, an industry watcher explains. Some chopping systems make this easy, he adds, with blades that can be regapped in a matter of minutes while others require hours of labor. Likewise, some firms offer blades with multiple cutting edges, greatly extending their useful life.
It’s also wise to clean the knife seat—the point where it’s mounted—after making a knife change, another firm notes. Otherwise, dirt that gathers under the knife could lead to cracking.
Indeed, overall cleanliness in a wire processing operation is viewed as a definite plus. One equipment manufacturer believes he can tell how profitable a yard is just by how organized or disorganized it seems when he visits. Another stresses that storing cable and wire where they’ll get contaminated with dirt and grit is a sure way to increase wear on your knives and thus decrease their useful life.
Finally, a smart processor will learn not to repeat some of the common mistakes made around wire processing equipment. Over- or undertorquing a machine’s fasteners is one such error, notes a manufacturer. Undertorquing can lead to bolts coming loose, he explains, while overtorquing can actually make bolts snap off. And nearly everybody makes the mistake—only once, he jokes—of leaving a tool on the infeed conveyor to their granulator. “They hit the start button,” he explains, “the tool drops in, and KABOOM!”
Whither Wire Equipment?
Unless the current trend of exporting unprocessed scrap wire changes dramatically, wire processors shouldn’t expect many innovations in the technology, some equipment manufacturers note. Indeed, one expresses reluctance to develop new machinery after making a new product that users had seemed to want, only to find few actual buyers. Another says bluntly: “Without growth in the wire processing industry, we won’t direct our engineering energies toward any new things.”
Instead, various manufacturers suggest finding new uses or outlets for existing technology. For instance, some see electronics recycling and scrap tire processing as natural fits for wire chopping operations that want to branch out. Another firm notes that a growing number of his scrap customers are buying prechopping equipment to install at their suppliers’ facilities so the suppliers can cut up the cable and wire on-site.
Such “forward-thinking” processors have reviewed the poor density in some of the roll-off boxes they pick up from suppliers, the manufacturer explains. Then, “when they examine fuel prices and other costs associated with picking up this scrap, they ask themselves, ‘Why do I pick up gangly, unmanageable scrap when I can have the customer downsize it for me?’”
As a result, the suppliers can devote less of their plant space to storing their scrap, the processors save time and money on collecting and preparing the material for granulation, and the equipment maker sells more equipment—a win-win-win situation all around.
Robert L. Reid is managing editor of Scrap. •
From stripping to chopping, wire processing machinery helps recover the metals that power our electrical age. But questions about the industry’s future also challenge its technology.