The study of thin kerf cutting forces has somewhat been limited over the last 70 years since the original work done on cutting forces by Kivimaa (1950). New interest in optimizing the sawing process to reduce the amount of sawdust has been kindled by the industry in Sweden. An effective approach to reduce the amount of saw dust, and therefore produce thicker wooden boards, is the use of thinner saw blades that create thinner kerfs. The use of thinner saw blades introduces a new set of problems such as instability, and therefore an unsafe work environment and poor surface finish on the boards. The starting point to analyse such instabilities and the vibrations of a thin sawblade (bandsaw or circular) is to analyse the cutting forces acting on individual sawblade teeth. Scandinavian winters can be harsh, especially in the north where temperatures drop well below zero. Sawmills process frozen wood in these temperatures and it is therefore important to analyse the effect of frozen wood on the cutting forces whilst testing different band thicknesses and clearances. The moisture content plays an important role in the cutting forces, especially in frozen wood and therefore the sapwood (SW) and heartwood (HW) was tested separately with different moisture contents (approx. 30-40% in HW and 110-150% in SW of green Spruce (Esping 1992)). The forces are defined in Fig. 1a where the main (FM1), lateral (FL1) and normal or feeding (FN1) forces can be seen. The most dominant forces, namely the main and normal force, were the main focus of this study.
Keywords: sapwood, heartwood, sawn timber, Picea abiesroperties
Authors
V. Meulenberg
M. Ekevad
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