Effect of variable engineered micro-geometry of the cutting edges of circular saws on the surface quality of SPF boards

The wood processing industry seeks to reduce maintenance and production costs while increasing productivity and revenues accordingly. Improving the surface quality of wood in the first phase of transformation helps to maximize the use of wood fibers. Variable engineered micro-geometry was applied to teeth of guided circular saws used in a bull-edger system, and its effect on the surface quality of SPF (spruce-jack pine-balsam fir) boards was assessed. Trials were carried out on a test bench with two types of saw blades: saws with up-sharp tips without edge modification, and saws with modified cutting edges based on a waterfall profile. Cants were fed at the rate of 145 m/min for a cutting speed of 2600 rpm resulting in a nominal feed per tooth of 1.33 mm. Saws with three levels of wear (after 0, 255, and 900 min of working at a sawmill) processed the cants under frozen and unfrozen wood conditions. A total of 336 board samples were produced. Surface quality of boards was assessed using standard parameters of roughness and waviness. The results revealed that the saw with modified waterfall edge profile showed better performance in terms of wood surface finish and wear rate due to the variable engineered micro-geometry. Frozen cants had a better surface finish. Roughness and waviness parameters were sensitive to changes in wear of tips.