Dubbskador på Alvestakubb

Sammanfattning: Mechanical harvesting may result in timber damages leading to reduced saw log quality. The initiator of this study was VIDA – a privately owned concern operating in the value-adding process industry of forest raw materials. The aim of this study was to examine the type and amount of damages on Alvestakubb caused by the harvester head during the cutting process. The aim was also to compare the damages caused by different types of feed rollers and to evaluate the effects of temperature on damage occurrence. Another purpose was to estimate the costs associated with stud damaged timber delivered to the VIDA sawmill in Alvesta. Data was collected from six harvesters with different combinations of feed roller and upper roller types. The damages were measured on 30 logs per harvester at two different occasions (frozen and non-frozen timber). Bark peeling, skidding damages and stud damages were found. The occurrence of stud damages deeper than 5 mm varied between 0 and 70 % among the different feed roller types. The temperature had both a positive and a negative effect on stud damage occurrence. Stud damages are present on a considerable share of the sawn timber resulting in costs due to quality loss. Adjustments of the cylinder pressure of the rollers, increased competence among harvester operators, development of new roller types and improved information systems are examples of measures to be taken to deal with damages on Alvestakubb.