Effects of log temperature, cutting width, and knots on the surface quality of the cants produced by a chipper-canter

The effects of wood temperature, cutting width, and knots on the surface quality of black spruce cants processed by a chipper-canter were evaluated. Four matched groups of logs were machined at temperatures of 20 degrees C, 0 degrees C, -10 degrees C, and -20 degrees C. Each log was transformed at two cutting widths (CW: 12.7 and 25.4 mm). Knot characteristics were measured on the cant surfaces after log processing. Surface quality of cants was assessed by roughness and waviness parameters and torn grain. The quality of surfaces was affected by the temperature of logs and cutting width. Poorer surface quality was obtained at larger cutting widths. This was caused by increased cutting forces when processing more material at larger cutting widths, compounded by the presence of knots. Waviness and roughness were higher for frozen logs than for unfrozen logs. Although the sub-zero temperatures caused higher cutting forces and vibrations, their effect was partly offset by the strengthening of the earlywood and the brittle behaviour of frozen wood. Correlations and regression analyses showed that the optimisation of the cutting conditions for decreasing waviness and roughness should also reduce the torn grain depth. Moreover, the position and area of knots could be considered to minimise waviness and roughness and the occurrence of torn grain.