How Wood Chippers Work

Wood chippers (or tree shredders) are frequently used in industrial lumber applications to reduce wood into chips or sawdust, as part of wood recycling or as part of a manufacturing process. Wood chippers are also used by those in the agricultural industry during property and land maintenance, or to aid in clean up after a storm or meteorological event. Typically, wood chippers are comprised of several distinct parts, including a hopper, a collar, a chipper, and a collection bin. An internal power source, typically a combustion engine, can range from 3 to 1,000 horsepower, depending on the size and type of chipper.

How Wood Chippers Work

Regardless of the size or make, wood chippers all function in the same basic manner. An internal engine, either an electric motor or a fossil-fuel engine, powers the device. A gearbox uses pulleys and v-belts to connect the engine to a set of knives—the pulley enables the engine to control the speed at which these blades rotate, and the v-belt transmits the power from the engine. Internal gears within the gearbox also help control speed and power.

Wood chippers typically have two separate chutes for processing wood. The first chute, the smaller of the two, shreds branches into chips. The second, larger chute features blades and additional devices, such as hammers, to turn excess plant material (such as leaves) into mulch. Based on the kind of blades within the chipper, a user can determine the type and thickness of wood the chipper is capable of handling. Typically, the larger the machine, the larger the load it can handle. Blades can either function on separate shafts or intermesh. If several blades are rotating on independent shafts, the wood will be repeatedly cut down the branches as they are passed through the blades at a fast pace. Intermeshed blades are somewhat slower, but are somewhat self-feeding as they draw the branches into the blades themselves. Additionally, intermeshed blades produce consistently sized chips.

Types of Wood Chippers

There are several kinds of wood chippers, ranging from those designed for residential use to larger, industrial models.

High-Torque Roller

High-torque rollers tend to be low-speed. Because they are also powered by an electric motor they are quiet, which makes them a popular choice for residential applications. Additionally, they are self-feeding, and some offer anti-jamming features.

Drum

Drum chippers are named for the large, motor-powered drum located at the center of the machine. The drum draws material in, like a feeder, and chips material while moving toward the output chute. The process is very fast and loud, and carries significant safety risks. Because the drum and engine are directly connected, any kind of drum jam can subsequently affect the engine, causing the engine to stall and pieces of wood to become lodged in the drum. Additionally, operators must exercise care when feeding the machine so as not to get clothing or appendages caught in drum, which can cause extreme injury or death. Some models offer additional safety features, which help ensure operator safety while also minimizing the sound of the machine.

Disc

A disk chipper features a disc, typically steel, with cutting blades attached. Material is drawn from the hopper via hydraulic wheels, and then moved toward the spinning disc. As the disc rotates, the blades encounter the wood, the material sliced into chips. With industrial disk choppers, the disc can be as large 160 inches in diameter, with an engine of up to 5,000 horsepower.