In the realm of horizontal, single-ram balers, there are two basic types of models: the open-end extrusion baler and the closed-end baler. The horizontal, single-ram extrusion baler is a high production baler, while closed-end models are geared more toward lower production. Most closed-end models are limited to a few bales an hour, while extrusion balers can produce up to four times that number.
One manufacturer says that “processors should be confident if they really only need a low-capacity baler. Closed-end balers have their place, but processors should not put themselves in a position that they will be regretting soon after their purchase.”
But others point out that even if processors expect to be processing at or slightly above the limit of a closed-end baler, they should consider making the investment in an extrusion baler. Many do so simply to avoid the hassle of having to manually tie closed-end bales.
In an open-end, horizontal, single-ram extrusion baler, a bale is made by compressing and squeezing material through a long extrusion chamber. After the first bale (called a plug bale) is made, the subsequent bales are made by pushing material up against the back of the forward bale. Since the extrusion chamber is open-ended, the first bale will be somewhat looser than the other bales because it only has the tension force of the wire to bale against (in addition to the side forces), and not another bale.
“These balers are perfect for operations that are moving large amounts of material like cardboard or paper,” says one manufacturer. “It is not designed for making one bale at a time. The material has to keep coming to make it a very efficient baler.”
The single-ram extrusion baler is best suited for baling all grades of paper and old corrugated cardboard, and it can even bale used beverage cans, steel cans and plastic bottles.
Generally, a processor can expect to get rates of about 10 to 15 tons per hour for UBCs; 20 to 25 tons per hour for OCC; 25 to 30 tons per hour for mixed paper; and 45 to 50 tons per hour for newspaper. Rates will vary according to the size of the baler, feed flow and baler options. There are even some extremely large balers that can bale higher throughputs – as much as 70 tons per hour for mixed paper.
Single-ram extrusion balers can cost anywhere from just under $100,000 to more than $700,000 depending on the model and its rated capacity. “You can buy a basic small model, or a very large one with very high output,” says one manufacturer.
Bale sizes vary between models, with widths from 33 inches to 43 inches; heights from 28 inches to 43 inches and lengths as short as 12 inches, or as long as the wire will hold and the bale is manageable. Some processors have produced bales 8 feet in length – the width of a shipping container.
Also, because an operator can vary the lengths of the bales, a bale of one material can be finished off and a different bale of new material started behind it without risking contamination. There are two ways to accomplish thisl. The first is to make a smaller bale with the leftover feedstock in the charge box; the second is to create an oversized bale by adding the material to the last bale.
These types of balers are extremely flexible, according to operators. One processor says his firm bales seven different types of material and may switch grades several times a day without a hitch. “It’s so easy to switch materials because, no matter how much material is left over, you can still compress it, tie it off, and get on with the next material.”
The single-ram self-adjusts to varying material grades to maintain proper baling pressures and reduce stalling. It is considered an energy-efficient design because the main force is concentrated at moving the material through the extrusion chamber, which squeezes and gives accordingly. In addition, a single-ram baler needs to power only one ram instead of two.
Despite all these strengths, single-ram extrusion balers also have limitations.
The first is that bale lengths can swell and differ by several inches, and this can be a concern when shipping. For instance, suppose the bale length counter (formally called a lamination counter) stops at 68 inches after the last stroke, and the designated bale length is 72 inches. If the next charge compresses 5 inches of material into the extrusion chamber, the counter will trip at 72 inches but can’t begin to tie off the bale until the stroke is finished. At that point, the extra inch of material has already passed the tie-off point, and the bale length will be 73 inches for that particular bale.
One way to combat this is to install a photo eye that will automatically control the amount of material entering the charge box and reduce bale swelling. By adjusting the photo eye, an operator can also eliminate a condition called the “banana effect”. This occurs when the density of the bottom of the bale is greater than the top of the bale. If the bottom material is denser, it will tend to expand more, swelling the bottom of the bale and causing the bale to assume a trapezoidal shape and to curve slightly. Using a fluffer will also help eliminate this problem.
The second limitation involves the types of materials that the horizontal extrusion baler can process. While this type of baler processes paper and OCC efficiently, it may not be the ideal baler for UBCs and plastic bottles, and it cannot bale metal extrusions. When compressed, extrusions can puncture the next bale, causing it to fall apart. In addition, the fingers that guide the wire for tie off may get bent.
Processors add that single-ram extrusion balers are not best suited for processing plastic bottles because the bottles can more easily expand (known in the industry as “regaining their memory”). This is because only five wire straps of annealed wire are used, and that type of wire is more ductile than the high-tensile wire used in two-ram balers. But proponents of single-rams simply say you can overcome this by making shorter bales or even adding on a cross-tie system. Other manufacturers say that they have reduced the tying tolerances to accommodate these materials.
Finally, a single-ram baler has a smaller hopper than a comparable two-ram model. This is because the hopper is limited by the width of the bale being made. Hopper widths can vary from 33 inches to 43 inches, and lengths may vary from 50 inches to more than 80 inches. But with a two-ram, the hopper can be as long as the length of the bale, so these hoppers can be as large as 60 inches wide by 110 inches long – overall, better able to accommodate more bulky material.
While several balers use pre-press doors or flaps that push material down below the shear blade to prevent jamming and have rams that travel on wheels, there is a new type of single-ram extrusion baler that uses a pre-press ram from the side of the hopper. This unit has the benefit of a large hopper that is 80 inches by 70 inches. This baler has been classified, actually, as a two-ram extrusion baler, with the second ram having compression force equal to the main ram.
“This gives you the best of both the two-ram action and the extrusion chamber,” says the manufacturer, “resulting in denser, more even bales and higher throughput.”
A closed-end, horizontal, single-ram baler is considered a low-capacity baler that can be used to bale OCC, paper, plastic bottles, UBCs, steel cans and other light metals. The baler’s lower capacity is due to the lack of a long, continuous extrusion chamber and the use of manual tie-off systems.
Most manufacturers recommend this type of baler for an operation that is processing about three bales an hour, or about 4 to 5 tons per hour. Single-ram, closed-end balers usually produce shipping bales that are 30 inches high by 45 inches wide by 60 inches long.
Costs for single-ram, closed-end balers are between $20,000 and $100,000.
In this type of baler, a single ram compresses material into a baling chamber and against a door, and then the bale is tied off manually. At this point, the back of the chamber opens, releasing pressure in the forward direction. As the baler continues to operate and more material is fed into the chamber, the finished bale is slowly pushed out with each cycle of the ram.
Another model simply uses an extended ram to eject the bale without having to add more material behind it. When the tied-off bale clears the door, it can be removed with a forklift. The door then closes, and the sequence continues.
On a closed-end baler, the door can open to either side, or raise vertically to provide for faster operation.
In a side-eject baler, material is baled into a chamber just like in the previous configuration, but this time pressure along the ram axis is exerted on a fixed wall. Unlike the door-eject method, material is not constantly fed behind the finished bale. Instead, pressure is relieved from the bale in three directions to achieve bale ejection out of the side of the baler after it is tied off. First, the ram is retracted, eliminating the end force. Then the side door is opened, relieving the side force. Finally, the hinged top of the chamber relaxes, relieving the vertical force on the bale.
When the pressure is relieved in all three directions, a hydraulically-powered server island at the base of the baling chamber protracts, carrying the bale with it. The island also allows the forklift operator to easily position the forks under the bale and eliminates the need for a separate pallet to be positioned at the exit point.
Tie-off methods for both side- and end-eject balers are usually manual and can be either top tie or side tie. Some manufactures have special guides to help speed up the tying process.
Since bales are made in a closed baling chamber, they are extremely uniform. “You get very square, exact and dense bales,” says one manufacturer.