The production of knot-free wood is important since the market demands wood without knots for reasons of both appearance and material properties. This work describes a simulation of the removal of knots from star-sawn timber and square-sawn. The efficiency of the two methods is compared in terms of the length of the knot-free components obtained and the volume yield.

The simulation is based on data for trees and logs taken from The Swedish Stem Bank. These data are then used to simulate the sawmill process in a computer program called the Virtual Sawmill. Data related to the boards obtained are then used in a MATLAB model simulating the cross-cutting of knots.

Simulated star sawing of logs with a top diameter exceeding 230 mm gave a mean knot-free component length of 417 ±321 mm, while the mean length of knot-free components for simulated square sawing of the same logs was 298 ±122 mm. The volume yield of knot-free components from the two sawing patterns was 91 % for star sawing and 87 % for square sawing. For timber with cross-section dimensions of 38 x 75 mm2, the mean length and yield of knot-free components from simulated star sawing were 451 ±349 mm and 90 % respectively. In simulated square sawing, the corresponding values were 263 ±197 mm and 82 % respectively. This shows that star sawing has a potential for the production of knot-free timber.