Effects of radial force and log position on the stem on ring-debarker efficiency in frozen black spruce logs

The effect of the radial force applied by a ring debarker tip to frozen black spruce logs, obtained at three positions on the stem, was studied. A one-arm ring-debarker prototype was developed, which controlled the radial force, rake angle, and cutting and feed speeds. The experiment consisted of debarking logs using three different levels of radial force. The rake angle (80 degrees), tip overlap (20%), and cutting and feed speeds were kept constant. Debarking quality was evaluated by two criteria: the proportion of bark remaining on log surfaces and the amount of wood in bark residues. Log characteristics (dimensions, eccentricity, and knot features), bark/wood shear strength, and basic densities of sapwood and bark were also measured. Experiments revealed that log position on the stem did not affect debarking quality. The results also showed a significant effect of the radial force: the amount of bark remaining on log surfaces increased and the proportion of wood in bark residues decreased as radial force decreased. The effects of log eccentricity, bark/wood shear strength, and the proportion of knot surface on the debarking quality were examined. These results give useful information to improve debarking quality within the studied range of radial force, log diameter, and debarking parameters.