An analysis of machine-caused lumber shape defects in British Columbia sawmills

Ideally, sawmill production results in lumber with edges that are parallel to each other and ends that are rectangular and in line with each other. However, abnormalities in the sawing processes cause deviations from this ideal shape. In the sawmill, these deviations, which are known as lumber shape defects, are often detected as off-size variations in thickness, and one particular defect shape is not necessarily distinguished from others in the downgrading process. In 2000, a survey was designed and implemented to determine the industrial significance of six major machine-caused lumber shape defects occurring in British Columbia sawmills: snipe, flare, wedge, taper, thin snake, and fat snake. The survey established that thin snake, snipe, and taper have the most serious impact on the industry. In addition, the survey identified three priority areas of focus for mills desiring to reduce their production of these defects, including ongoing monitoring and control of piece stability, saw condition, and alignment.