Aplicação de microesferas de vidro para avaliação da qualidade da superfície serrada da madeira de Eucalyptus grandis

Abstract

The use of machinery and software is growing in sawmills in order to increase the sawing yield. These measures also seek to improve the quality of sawn timber, given that warping, size variation and defects in the surfaces of the sawn pieces increase losses during finishing operations. Little is discussed in the literature concerning the surface quality of lumber. This occurs due to the shortage of evaluation methods. Therefore, the main objective of this study was to evaluate the quality of the sawn surface of Eucalyptus grandis lumber, after log sorting, defect analysis of the sawn pieces and yield calculation. For this, logs were sorted into four diameter classes. We evaluated their tapers, flattening and end checks. The sawing method was planned by Maxitoras® software - Optimber, and was compared with the actual yield. The quality of the sawn timber was assessed by measuring warping and size variation, as well as evaluating their surfaces by applying glass microspheres, based on the E-965 (ASTM, 1996) method. We concluded that: i) the shape of the logs was considered acceptable, according to the usual classification methods, however, the end check values were higher than the values found in literature; ii) the warping of sawn pieces was considered of high intensity, while the size variation of the lumber, with frequency in 17% of the pieces, was classified as acceptable; iii) the actual yield obtained from sawing was equal to 49.8%, which on average was 16.3% lower than planned; iv) the method for evaluating surface quality of the lumber, by using the height of the stain glass microspheres, showed viability and that the surfaces of the sawn pieces of the outer parts of the log were rougher than the parts removed from the intermediate and internal positions of the logs, regardless of the diameter classes. The values of the height of the glass microsphere stains were equal to 0.1896 mm, 0.1529 mm and 0.1466 mm for these three positions, respectively.