Sanding and Shaping Characteristics of Gmelina arborea Grown in Two Ecological Zones in Ghana

Abstract

Poor machining of wood generates more residues which leads to low recovery in wood processing. Therefore, the availability of appropriate wood machining techniques would promote efficient utilization of logs. This study looked at the shaping and sanding properties of Gmelina arborea - a lesser-known species in Ghana - in order to promote its efficient utilization. Six trees from plantations at the Wet Evergreen and Dry Semi-Deciduous Forest Zones were extracted and processed into lumber using LT 15 horizontal wood-mizer. The average moisture content of samples just before the test was 14.57%. Specimens were prepared in accordance with ASTM D 143-83 and ASTM D 1666-87 (2004) for the sanding and shaping tests. The effects of tree location, grit size and spindle speed on sanding and shaping properties of Gmelina arborea wood were assessed using the visual approach. For the sanding test, grit size P80 was the best sandpaper to remove chipped and torn grain defects from the surfaces of Gmelina arborea lumber after planing. Spindle speed 10,000 rpm gave the best shaping output so it was recommended for shaping Gmelina arborea timber grown in Ghana. For the shaping operation, wood samples obtained from the Dry Semi-Deciduous Forest Zone had better surface quality than those obtained from the Wet Evergreen Forest Zone. A similar trend was obtained for the sanding test. The most common defects observed during grading of the shaped specimens were raised, chipped and fuzzy grains and those observed for the sanded specimen were fuzzy and scratchy defects. At 5% level of significance, tree location and spindle speed had significant effect on the surface quality of the shaped specimen.