VK butt reducing is carried out with a butt reducing rotor integrated in the debarker, which is always mounted in the first rotor position of the machine frame before debarking. The power transmission from the electric motor to the reducing rotor is carried out by using V-belts.
The butt reducer cuts wood crosswise towards the log’s infeed direction. For this reason, the power required is significantly greater when compared to the debarking process. Holding the log during reducing requires a lot more holding force from the feedrolls, whereas in the debarking process, the bark is only abraded away from the wood surface. The pressure level of the feedrolls is adjusted automatically to a higher level.
The reducing tools are mounted on the reducing ring, which is mounted on a rotary wheel. The log is fed through the reducing ring. The reducing tool is mounted on the side of the opening cut, removing a maximum of 10 cm from both sides (reducing a maximum total of 20 cm). The debarker continuously follows butt diameters and the program reduces the feed speed automatically with large butts, if needed.
The reducing ring opening is fixed. The operator has rings of different openings (usually three to four pieces) in use, which are used according to the log’s diameter class. The rings are locked in the “rotor pulley” with a reliable locking system. The reducing ring is unlocked and the ring is changed with a separate hydraulic change-over device delivered with the debarker, which also functions as a storage holder for the rings. Changing a reducing ring takes about five minutes.