EFFECT OF KNIFE WEAR ON SURFACE QUALITY OF BLACK SPRUCE CANTS PRODUCED BY A CHIPPER-CANTER

摘要

Effect of knife wear on surface quality of black spruce (Picea mariana (Mill) B.S.P.) cants machined by a chipper-canter was evaluated. A set of eight canting knives with six levels of edge recession (207, 290, 349, 449, 519, and 549 pm) was studied. Logs were fed at 145 m/min through the canter head rotating at 726 rpm yielding a nominal feed per knife of 25 mm. For each edge recession, two sides of the logs were machined at either unfrozen (above 14 degrees C) or frozen (below -23 degrees C) wood temperatures. Laserscanned profiles across the grain of 16 knife marks on each cant were evaluated for roughness and waviness parameters and depth of torn grain. The results showed that, regardless of log temperature, waviness and roughness were positively affected by edge recession. Roughness was more sensitive than waviness to changes in edge recession. Surfaces in general were smoother in frozen logs than in unfrozen logs. Maximum depth of torn grain appeared to not be significantly affected by knife wear. The results provided useful information for improving the performance of the chipper-canter in terms of surface quality.