Finding Your Style

Baling is a simple concept. Material is gathered into a chamber, which gives the bale its size. Most balers then apply some form of strapping to hold the bale together.

THE MAKING OF A BALE

The flow of material starts with loading the hopper. Whatever means is used—conveyor, front-end loader, etc.—the material must fit into the hopper opening. Material that does not fit easily into the hopper opening, whether individual pieces or large clumps, can cause hopper bridging. Bridging occurs when material lodges against the hopper walls in such a way as to structurally support its own weight and, therefore, does not fall into the baling chamber. This is a serious condition requiring operator intervention. Hoppers should be sufficiently large enough to accommodate the material to be processed, with smooth walls (a slight negative taper can be advantageous) and no ledges to catch the corners of cardboard containers. The volume of material the hopper can accommodate can be much larger than that of the bale chamber.

There are two main ways of controlling the compaction of material from the loading chamber into the baling chamber: lids and shearing. Lids swing to pre-compress the material in the hopper down into the loading chamber. If done well, the material can then be compressed into the baling chamber. The problem comes with having the correct amount of material in the hopper before the lid actuates. Too little material makes a light bale, and too much material creates a jam—the lid cannot force the material into the loading chamber, so the platen cannot move forward and the material must be removed manually.

Shearing of the material is accomplished by having one blade on the upper edge of the platen and one on the frame where the platen enters the baling chamber. These blades shear off the material above the platen so that only the material in front of the platen gets compressed into the baling chamber. This technique can be versatile because the number of strokes of the platen is varied to build the desired bale size, no matter what the type or density of the material being baled.

Shear knives are available in serrated and flat styles. Typically, serrated knives are recommended for most applications, with the exception of heavy-duty nonferrous metals, where a flat knife is recommended.

A well-designed shear-type baler can produce a denser bale, especially on the top surface. The platen then provides for the compressing force as well as the shearing force. Therefore, caution is advised when selecting the baler cylinder. The amount of material that the cylinder force will be required to shear is proportional to the width of the loading chamber (the width of platen), the length of the loading chamber and the height of the material in the hopper. The weight of the column of material creates higher density on the bottom of a pile.

THE SUBSTANCE BEHIND THE STYLE

Now that I’ve covered the mechanics behind producing a bale, I’ll review some common baler styles.

Closed-end balers have a completely enclosed baling chamber. After the bale is formed and strapped, a door is opened, allowing the bale to be ejected from the machine.

Open-end balers, however, utilize a bale-retention chamber that holds the previously finished bale against the new bale being formed. This type of baler is often faster and allows for more automated operation than closed-end models, as bales are formed continuously. However, some material can be difficult to keep in the retention chamber, which can be a potential downside of using this style of baler.

Two-ram balers feature a door to contain the bale under compression. The door closes off the exit in the baling chamber so that materials that flow easily under pressure, such as solid waste, are restrained into the desired bale shape until the bale is ready to be ejected.

Two-rams are designed and built to withstand extreme rigors of multiple material applications, producing high-density bales. They typically use higher shearing and baling forces and are typically used in applications involving tougher to bale material (material featuring more memory) as well as greater volumes of material.

A “narrow chargebox” two-ram baler features a smaller footprint than a “wide chargebox” model but can have just as much versatility, though at a lower production rate, and a lower price. Narrow-box models should be used for operations processing less than 500 tons per month, while wide-box models are better suited for operations processing more than 500 tons per month. Two-ram balers can process a multitude of materials, including but not limited to OCC (old corrugated containers), ONP (old newspapers), high grades, PET (polyethylene terephthalate), HDPE (high-density polyethylene), plastic film, foam board, plastic drums, nonferrous metals (aluminum sheet, clips, skeletons, extrusions, radiators, copper, certain types of stainless steel, certain aluminum shapes and wire), white goods, municipal solid waste and other specialty materials.

THE BEST PERFORMANCE

After selecting the appropriate baler style, prospective buyers should look for manufacturers that provide training in maintenance and operations as well as equipment that provides self-diagnostics and troubleshooting on the operator’s console or panel.

The most common problem we hear of with baling equipment is what customers view as a lack of service after the sale. Normally this issue arises from minor problems that are easily corrected if proper guidance is received from the factory in a timely manner. While today’s technology and equipment does not totally eliminate these minor problems, the machine’s diagnostics capabilities can direct the operator to the source of the malfunction or problem, helping to resolve the issue more quickly.

Today, many options are available in baling equipment. Recyclers should use caution when determining the beneficial from the non-essential options for their particular applications. The list of options is too numerous to list but includes motor-starting arrangements, conveyor support equipment, bale tables, material conditioning equipment, etc. Customers can choose among available options to optimize a baler’s performance for their specific needs.

The author is R&D manager for Harris, Tyrone, Ga. He can be contacted at ed.simpson@harrisequip.com.