Portable woodchippers are used to break logs into smaller chips for biofuel, manufacturing or recycling. There are three main components to the chipping machine: a hopper to feed the wood into the machine, a chipper mechanism and a collection bin.
The chipper mechanism is traditionally a rotating steel drum with reinforced steel blades along its length. The wood is drawn in by a combination of gravity and the rotation of the drum. Drum chippers rapidly break wood down, but are noisy and create large, uneven chips. Newer woodchippers use a steel flywheel instead of a drum. The wood is fed into the chipper on hydraulic rollers and blades on the face of the flywheel cut against a fixed anvil plate, producing uniform woodchips. Behind the disc are serrated paddles, which break down any bigger chips before the cut wood is ejected into a container.
Much larger ‘whole tree chippers’ have carbide flail hammers, which pulverise the wood by mechanical force rather than by cutting. These are very heavy and are usually towed by a truck.