The main function of wood chippers is to reduce the space taken up by piles of wood refuse, and to enable easier transportation of the refuse to another site. Chip uniformity becomes an issue only when the refuse to be shredded is to be used for biomass heating purposes. The three types of chippers--drum, disc and screw--are differentiated by the types of blades they use, and how those blades are positioned along a rotating axis.
Drum chipper
Drum chippers are characterized by a parallel-sided rotary drum, with attached knives running down the length of its axis.Working in tandem with the rotating knives are chip breakers, positioned behind the knives at right angles to the blades. Drum chippers generally produce less uniformly sized wood chips than disk chippers, and are primarily used by park workers and land developers to clear forest underbrush more easily.
Disk chipper
Disk chippers use a flywheel, composed of a large steel disk positioned at a right angle and possessing chopping blades with slotted disks. These blades slice into the tips of the wood refuse as it's pushed into the chipper on a roller belt. Oppositional cutting action is supplied by a knife, positioned in the throat of the disc chipper. Knives in a disk chipper can be curved or straight, depending on the model.
Screw chipper
Screw chippers are constructed entirely differently than disk or drum chippers, in that the interior blade is one continuous, conical, screw-shaped blade. This long spiral blade possesses sharpened edges for hacking up wood refuse. The rotation of the blade is set parallel to the direction of the wood refuse in-feed opening, with the wood being pulled in by the spiral motion of the blade.
