Abstract

Thermal modification is widely used to improve wood's dimensional stability and durability, but it also alters its mechanical properties-and with them, its machinability. This study investigates how thermal treatment intensity and machining mode (climb vs. conventional cutting) affect cutting forces and surface roughness in ripsawing of southern beech (Nothofagus alpina). Three material conditions were compared: untreated control, Treatment 1 (170 degrees C), and Treatment 2 (190 degrees C). A full factorial design including override and mean uncut chip thickness as factors was analysed using multifactorial ANOVA, with density and moisture content examined through correlation analysis. Thermal treatment significantly reduced both mean and maximum cutting forces, with T2 showing peak force reductions of up to 30% compared to the control. Mean uncut chip thickness emerged as the strongest predictor for both forces and roughness. Although machining mode showed a statistically significant effect on force magnitude, the practical difference was small (approximately 2.5 N), and its influence on surface quality was more decisive: climb cutting produced approximately 1 mu m lower arithmetic average surface roughness (Ra) than conventional cutting. Override also played a significant role, with 10 mm minimising cutting forces and 15 mm increasing surface roughness. Moisture content showed no significant correlation with forces nor with roughness, confirming its negligible influence within the studied range. Density and thermal treatment were the key factors governing cutting forces, whereas cutting mode and mean uncut chip thickness primarily determined surface finish. These findings confirm that thermal modification enhances machinability by reducing cutting resistance, while climb cutting improves surface roughness without additional mechanical load-particularly when combined with a 10 mm override. The results offer a predictive basis for optimising industrial milling of thermally modified wood.