January/February 2012
Automatic wire-tie systems make baling safer, faster, and less labor-intensive, but recyclers must know certain technical, maintenance, and baling wire basics to get the most from this equipment.
By Theodore Fischer
For more than 30 years, recyclers have realized the benefits of balers with automatic wire-tie systems, or auto-ties. Such systems reduce labor costs because they don’t need workers to manually tie wire straps around bales. Auto-tie manufacturers frequently boast that their systems are “hands-off” operations that require only someone to haul away the finished bales. Fewer people involved in the baling process also reduces the potential for injury. Auto-ties lower processors’ material costs by using baling wire more efficiently. And they create tighter, denser bales, which is a plus for scrap companies that ship overseas. “To get as much material as possible in 40-foot overseas containers, you need really square, compacted bales,” one baling wire distributor says. “Auto-tie machines have become extremely popular because you get more compaction, a bale that’s more of a cube, and a lot more weight per square foot in the containers.”
With these advantages, auto-ties can be a powerful blessing, but they also can be a mixed blessing, recyclers say. “When auto-ties work right, you love them,” says Marty Davis of Midland Davis Corp., a scrap processing company in Moline, Ill. “But most people will tell you auto-ties account for most of the downtime for a baler with that type of equipment. You have to maintain a certain number of parts on hand [to fix things] that typically go wrong.” Auto-tie manufacturers say they continue to improve the reliability of their systems, making this equipment more valuable—and less of a headache—to recyclers.
Baler and Auto-Tie Basics
Balers come in two basic configurations—vertical and horizontal—with automatic wire-tie systems offered exclusively on the latter. Vertical downstroke balers are common in grocery stores and home improvement centers for crushing corrugated containers, though some recyclers also use them to compact paper, light nonferrous metals, and copper wire. They have a single hydraulic cylinder on top that pushes a compression ram down into a rectangular charging box to press the material into bales. These are hands-on operations: Workers must manually load material into the machine and bind the bales, using roughly 14-foot lengths of baling wire.
Most larger recyclers operate horizontal balers that create bales by compressing material horizontally rather than vertically. These balers, effective for processing plastics and metals as well as paper and corrugated, come in three basic configurations: single-ram, closed-end balers, often used for baling slippery material such as PET, HDPE, or coated paper; single-ram extrusion balers, touted for their ability to handle a high volume of material relatively quickly; and two-ram balers, valued for their versatility as well as their capacity. Auto-ties are almost always found on either single-ram extrusion balers or two-ram balers. “To manually tie a bale of paper, plastic, or aluminum cans just isn’t feasible,” Davis explains. “Auto-ties make the horizontal baler feasible” for processors of those materials.
Auto-tie systems connect to the discharge area of the baler. Though the tying mechanism on a single-ram extrusion baler is different from that on a two-ram baler, the general principle is the same: As material emerges from the baling chute, the system automatically encircles the material with wire, tightens the wire, twists it into knots, and cuts it. The number of wire strands needed around the bale depends on the material being processed, though five wires per bale is common. Material with excessive “memory,” such as plastic bottles, requires more strands than material such as sheet metal, which holds together tightly on its own. Auto-ties typically operate based on programmable controls, some of which come with touch screens.
Baler manufacturers purchase auto-tie units and offer them as options on their balers. Thus, baler customers usually have no choice in the brand of auto-tie equipment they get. Balers without auto-ties often can be retrofitted with this equipment. Manufacturers of auto-ties compete on features such as
--feed and tension speed, which is expressed in feet per second, usually ranging from 8 to 14 feet;
--style of knot produced, identified by the number of “twists”—usually three to four, though one wire manufacturer pinpoints the ideal number of twists at 3¼; and
--cycle time, measured in seconds to produce and twist a wire, number of ties per hour, or both. One manufacturer notes that overall cycle time varies based on the bale’s size and the baler’s opening.
Every auto-tie manufacturer also claims its systems have unique attributes. One company says its spreader bar houses 80 percent of its machine’s wear parts, such as twister pinions, bushings, and cutters, which makes it easier to perform maintenance. “By removing two pins, you flip up the yoke, and it’s all right there,” a sales manager says. “You can change all your wear parts in less than five minutes, as opposed to 30 to 45 minutes in the older models, so there’s no downtime.” In addition, with this unit, the operator can change wear parts while
a bale is in the chamber.
Another company attributes the success of its 30-year-old model to its speed (a three-second cycle time, or potentially 1,200 straps per hour) and versatility (able to accommodate virtually any recyclable material). The company’s 20-year-old, higher-tech unit has advanced, solid-state electrical controls and systems and the capacity to use a wide range of galvanized wire (10 to 13 gauge), with which it produces a four-twist knot.
This manufacturer’s latest auto-tie model features what it calls the industry’s first removable core, which contains 80 percent of the system’s wear parts. Users can take the entire core out of the machine, replace it with a spare, and get the unit operating again in less than five minutes, the company says.
Another manufacturer’s wire-tie system for two-ram balers can create shorter, 7.6-inch wire knots using 9- to 12-gauge wire. Equipped with an ambidextrous accumulator and payoff arm that can be set to provide operator access on the right or the left, this unit allows the wire entry to be mounted tightly against the baler. Its 120-inch, reinforced crossover tube encloses the wire, and an anti-fouling wire payoff ensures smooth, consistent wire feeding and allows operators to change wire stands without using tools.
Though prices for wire-tie systems vary, they begin around $25,000, either installed on a new baler or retrofitted to a baler in the field. As a rule, auto-ties do not come “off the rack.” Each system “has to be custom-fitted to the baler,” says one manufacturer. “The chamber openings are different, depending on the kind of baler you have. We build to order, basically.”
Recyclers interested in adding an auto-tie system to an existing baler should be prepared to answer questions like those on the retrofit questionnaire one manufacturer sends to prospective customers: What is your baler’s brand and model number? What material does the unit bale, and does it include liquids? What is its production rate? Does the baler have a release door? Can your hydraulic source provide 13 gallons per minute at 1,200 pounds per square inch? Can your electrical source provide clean 110 volts/10 amps of power? What is your desired wire size? Are the wire infeed and control box to the right or left when facing the strapper and discharge nozzle? Do you have any control interface or special control considerations? What’s your desired delivery date?
Ties That Bind
A key component of every auto-tie system, of course, is the wire it dispenses. There are two principal types of baling wire: galvanized and black annealed. Galvanized wire, which is coated with zinc for corrosion protection, is made from high-carbon wire rod, which gives the material maximum tensile strength, one wire manufacturer says. “People like galvanized wire because it slides easily, it’s slippery, it’s easier to cinch down, and it’s less prone to rust when stored outside,” a wire vendor says, noting that the majority of his customers buy galvanized wire. Galvanized wire typically is more expensive than black annealed wire, however, and its higher tensile strength reduces its elongation capacity—the amount of stretch, or give, in the wire—which means it’s more likely to break than lower-tensile, higher-elongation wire.
Black annealed wire, which has a black oxide finish to prevent rust, is somewhat softer because it’s made from a medium-carbon wire rod, which gives it “a good balance between tensile strength and elongation,” one manufacturer says on its website. Some recyclers use black annealed wire “because the slipperiness of galvanized wire works against you if you’re looking for nice, tight tie-offs,” the wire vendor says.
Baling wire comes in various gauges, normally ranging from 11 to 14 for
scrapyard baling purposes. Gauge numbers refer to the diameter of the wire, with the wire’s size—and, hence, its strength—decreasing as its gauge increases. An 8-gauge wire, therefore, is thicker and stronger than a 14-gauge wire. The goal for many recyclers is to save on wire costs by using the lightest gauge wire that still will do the job. Auto-tie wire is sold by the pound in 50- and 100-pound boxes as well as in spools, or coils, that can weigh 1,500 to 2,000 pounds.
Though baler manufacturers recommend the best wire for their machines, the baling wire you should use depends mainly on what material you’re baling. “You want a heavier gauge if you’re baling commingled scrap—metals, plastics, foam, and materials that have more memory—just to make sure it has the strength,” one wire seller says. “If you’re just baling something like newspaper or corrugated, you can maybe go a little bit lighter gauge to get more payoff for the wire—more footage per spool.”
The brand of wire you buy makes a difference, wire manufacturers say. “People say ‘wire is wire,’ but sometimes a manufacturer will run annealed wire through its furnace a little bit longer, or it might put a little more zinc on galvanized wire,” a wire manufacturer says. “It’s important to know the elongation of the wire and its tensile strength because big scrap dealers, towns, or cities can make bales in excess of 1,800 pounds, and if the wire breaks, it’s not going to be pretty.” Steel wire can be annealed, or heat-treated to achieve specific metallurgical properties, in either a strand or batch process. In the strand process, the wire is heated for a specific number of minutes then cooled rapidly, one manufacturer explains on its website. In a batch process, the wire is heated for several hours then cooled slowly. The manufacturer calls it a “metallurgical fact” that the longer heating and slower cooling cycle of batch annealing gives wire much greater elongation—a minimum of 25 percent in a 10-inch sample—than strand-annealed wire.
The bottom line is, you have several wire choices for your particular operations. Davis says he relishes the higher quality of wire now available for his recycling operation. Wire manufacturers “have made improvements in the wire, so maybe you can use one gauge lighter wire than you previously used, which will have some net weight savings over time,” he says.
Staying Fit to Be Tied
Regular preventive maintenance is essential to keep auto-ties functioning properly and prevent them from idling your entire baling operation. “What happens is, if the machine isn’t maintained properly, the wire gets jammed up in there or the tie isn’t tight enough,” one equipment dealer says. “There are [wear] parts that periodically have to be replaced—guides that direct wires around the machine, rollers that force wires around the tracks.” Poorly maintained auto-ties can tie baling wire improperly, causing bales to break apart, which can lead to operational and safety problems. Regular maintenance, such as regularly changing the unit’s oil and keeping it clean, also reduce overall wire waste and maximize uptime. Auto-tie vendors offer training to their customers, either at the customer’s location or general training at central sites nationwide. One manufacturer’s training course covers topics such as machine operation, settings and adjustments, preventive maintenance, safety, and troubleshooting.
Auto-tie maintenance also is vital for operating these systems safely. Like the balers to which they’re mounted, auto-ties can pose a variety of potential safety hazards. “A wire-tier on a baler is a very dangerous place, where wire comes shooting around that track very quickly,” one manufacturer says. “Always have safety glasses on when you’re near it,” Davis advises, “because wires can break or fly around. If you don’t have safety glasses on, you could catch something in your eye.”
In the past year, one manufacturer came out with what it calls “wing guards” that mount to the frame of its auto-tie systems and “protect personnel from loose wire and anything like that.” The auto-tie manufacturer with the removable core technology says its system has a safety latch feature that allows a worker to remove the core and clean out hard-to-reach obstructions safely and quickly. The worker can take the core to a safe work station, where tools are readily accessible, to make repairs.
New Directions
Though few in the baler industry anticipate revolutionary auto-tie changes in the near future, new tweaks continue to appear. For example, one manufacturer of auto-tie balers for single-ram extrusion balers now offers a hydraulically driven gear twister that eliminates twister hooks and produces a knot with no pigtails, the extra wire beyond the knot. The company says this innovation cuts wire consumption and related costs by at least 10 percent.
Another dealer is excited about an “interesting wrinkle” on the auto-tie from overseas. As he explains, “most American brands drive the needle carriage with a double roller, and some models do it with a hydraulic cylinder. The imported balers use a combination of the two. I don’t understand why it’s so much faster, but it is faster.”
The same foreign manufacturer also produces an unusual auto-tie system for single-ram, closed-end balers, he adds. Most such balers are manual tie, though a U.S. manufacturer made an auto-tie version of its single-ram, closed-end baler years ago. With such a baler, users can more easily handle slippery materials like plastic bottles and get the speed, efficiency, and safety advantages of auto-ties without the expense of a two-ram baler, the dealer explains. This new system “fills a nice niche” and gives recyclers another auto-tie option, he says.
Theodore Fischer is a writer based in Silver Spring, Md.
Automatic wire-tie systems make baling safer, faster, and less labor-intensive, but recyclers must know certain technical, maintenance, and baling wire basics to get the most from this equipment.