Radially sawn timber?the Primwood Method for improved properties

Abstract

A new manufacturing system, the PrimWood Method, has been proposed to improve the utilization of wood. A basic concept within this method is the sawing pattern called star sawing, which produces timber with both rectangular and triangular cross sections. This method facilitates an efficient production of radially sawn timber with vertical annual rings, without juvenile wood.The sawn timber produced in the PrimWood Method is used to produce high quality, knot-free solid wood panels with vertical annual rings. In this process, the timber is finger jointed to form knot-free lengths which are glued together into a block. This block can then be divided according to thickness into thinner panels with vertical annual rings. In star-sawing, a certain volume of clear pieces are obtained which are relatively long, i.e. longer than 1 metre. It is not desirable to finger-joint these pieces, but instead to use them to manufacture products without any finger-joint.The PrimWood Method has been tested in an industrial plant. The manufacturing system was designed for a sawing capacity of about 30 000 m

Variation in log quality and prediction of sawing yield in oak wood (Quercus robur)

“…The objective of the sawing was to provide the largest number of quartersawn or at least partly quartersawn planks of target dimensions 70×170×3,000 or 70×120×2,000 mm. These were the preferred pieces in this study because the sapwood is often located at the edges and the dimensions are stabler during drying than in plainsawn planks (Sandberg 2005). If the shape of the log (crookedness, ovality and other features) did not allow the sawyer to identify the most appropriate circumferential log orientation on the carriage to achieve the objective, the log was systematically rolled so that the north face (previously marked on the standing tree) faced upwards.…”

“…4) because the timber was piled up and dried slowly. In addition, most of the graded pieces were quartersawn planks and this type of timber is dimensionally more stable during drying (Sandberg 2005), although it dries more slowly because water readily passes through in a radial direction. Therefore, distortions can be left out to classify air-dried quartersawn oak timber (the possibility of excluding distortions of the grading rules is already included in the UNE 56544:2011 standard).…”

“…Air drying can be accelerated by piling planks with larger spaces between the planks in each line and using larger fans to force air through piles and also by separating the piles from each other. During kiln drying, the air conditions in the kiln are modified depending on changes Sandberg (2005) in the current wood moisture content over time. Although the drying process speeds up at high temperatures, there is a greater risk of drying defects occurring when more intense (faster) drying schedules are used.…”

Checking of Radially Sawn Scots Pine and Norway Spruce Wood

“…Due to the anisotropy, tangential surfaces shrink more than radial ones during drying. Consequently, one suggested solution to minimize checking has been the setting of sawing direction of timber so that the proportion of radial surfaces is maximized compared to tangential surfaces [7]. Sandberg and Söderström [8] carried out an experiment in which the check formation of radially and tangentially sawn Scots pine and Norway spruce was followed in outdoor conditions for several years.…”

“…Besides the effect on moisture dynamics and checking tendency, there are also other purposes to optimize the sawing pattern between tangential and radial, such as visual outlook (grain pattern, knot structure), surface hardness, and performance in gluing and in surface and pressure treatments [11] [12]. On the other hand, the sawing pattern has effect on volumetric and value yield, time expenditure and costs in the sawing process that are of high importance for the saw mill [6] [7] [13] [14].…”