| Tension wood is a complex tissue with characteristics not found in normal wood. Its main feature is the presence of a G-layer. It also has relatively few vessels and low lignin content. Tension wood is more difficult to machine than normal wood and produces a fuzzy surface that affects quality and aesthetics, which is a problem for wood industries. If fuzzy grain is reduced in primary wood processing like sawing, then, the lumber will have an improved appearance before other machining processes take place, which would reduce manufacturing costs.; The principal objective of this study was to find a solution to the fuzzy grain problem. Small blocks of green and dry tension and normal wood of sugar and red maple were cut, using normal wood as a control. The forces (principal, lateral, and normal) acting on a sawtooth mounted on a three-axis piezoelectric load cell were measured. Green tension wood requires less force (principal and normal) to cut, contrary to the common belief that tension wood requires more energy to process than normal wood. This is apparently due to the amount and type of lignin present, and also that tension wood has thinner cell walls. It was observed that cutting forces increase when the grain angle increases. In frozen normal wood, the principal force was nearly as great as for dry wood, and the force was least for green wood.; Fuzzy grain is composed of bundles of cells that remain united along with a few individual cells. The bundles are formed by separations of cells on the surface of the bundle at the compound middle lamella. Formation of fuzzy grain and its severity are intimately related to slope of grain. When a sawtooth cuts the wood even at small angles, fuzzy grain is produced; however, when the sawtooth cuts the wood following the grain exactly (parallel to it) fuzzy grain is greatly reduced or even eliminated. There is also a relationship between fuzzy grain development and lignification of tension wood. Tension wood fibers are not well lignified and contain less syringyl lignin, and the cells separate easier. |
