A guide to manufacturing rotary veneer and products from small logs

This manual on the production of rotary wood veneer and associated manufacturing of veneer-based products draws on the results from completed ACIAR projects. It provides extensive information and guidance on the processing of small log resources into veneer, along with the description of manufacturing techniques to convert the veneer into high-value engineered wood products suitable for a range of appearance and structural applications

Increasing the Value of Forest Resources through the Development of Advanced Engineered Wood Products

The principal objective of this project was to deliver and validate technologies to transform low-value forest resources and sub-optimum quality logs into high-value construction and appearance products suitable for Australian and international markets. The project was designed to achieve this objective through a methodology that focused on forest resource, new technologies, market and economic aspects. Critical to the project design was direct participation and guidance by forest industry stakeholders

High value timber composite panels from hardwood plantation thinnings.

Identifying processing strategies and products that suit young plantation hardwoods has proved challenging with low product recoveries and/or unmarketable products being the outcome of many trials. The production of rotary veneer has been demonstrated as an effective method for converting plantation hardwood trees. Across nine processing studies that included six different plantation species (Dunn’s white gum, spotted gum, Gympie messmate, spotted gum hybrid, red mahogany and western white gum), simple spindleless lathe technology was used to process 914 veneer billets totally 37.4 m3

Processing small diameter logs from sub-tropical species

Small spindleless veneer lathe technology was used to produce veneer sheets as an alternative processing option to optimise the use of small log plantation resource. Thinned (300 spha) and unthinned control (1000 spha) plantings of 10.5-year-old Corymbia citriodora ssp. variegata (CCV) and E. dunnii (Dunn’s white gum) grown in two contrasting sites from climatic regions with large annual rainfall differences were studied. Overall veneer gross recoveries ranged from 50% to 70%, which were up to 3 times higher than typical sawn green-off saw recoveries from small plantation hardwood logs of similar diameter. Major limiting factors preventing veneer from meeting higher grades were the presence of kino defects and encased knots. Splits in E. dunnii veneer also contributed to reduced grade quality. Differences between two thinning treatments for veneer properties and grade recovery were generally small. There was significant evidence of site and species differences on veneer quality. The good quality site with higher rainfall in northern New South Wales produced denser and stiffer veneers with higher grade recoveries. CCV is a superior structural veneer species with high wood density and hardness as well as very good veneer stiffness exceeding 15,000 MPa but Dunn’s white gum has also demonstrated good potential as a useful structural plywood resource. Results indicate that relatively high veneer recoveries were achieved for the sub-tropical plantation hardwoods combined with very superior mechanical properties which suggest that veneer production have suitable attributes for a range of engineered wood products including plywood and laminated veneer lumber

High value timber composite panels from hardwood plantation thinnings.

Identifying processing strategies and products that suit young plantation hardwoods has proved challenging with low product recoveries and/or unmarketable products being the outcome of many trials. The production of rotary veneer has been demonstrated as an effective method for converting plantation hardwood trees. Across nine processing studies that included six different plantation species (Dunn’s white gum, spotted gum, Gympie messmate, spotted gum hybrid, red mahogany and western white gum), simple spindleless lathe technology was used to process 914 veneer billets totally 37.4 m3

Capacity and reliability of LVL beams manufactured from juvenile hardwood plantation logs

This paper summarises parts of the research outcomes of a university-government collaborative project aiming at determining the capacity and reliability of veneer-based structural products manufactured from early to midrotation (juvenile) hardwood plantations logs. Two species planted for solid timber end-products (Eucalyptus cloeziana and Corymbia citriodora) and one species traditionally grown for pulpwood (Eucalyptus globulus) were studied for the manufacture of the new products. Focus of this paper is on LVL beams. To cost-effectively determine the nominal design bending strengths of the new beams, a numerical model was developed. The model was found to accurately predict the strength of LVL beams with an average predicted to experimental ratio of 1.00 with a low coefficient of variation of 0.10. Using an established probabilistic database of the material properties of the veneered resources as model input, Monte-Carlo simulations were then performed. The design strength of the new LVL beams was established and found to be comparable to, and in some cases up to 2.5 times higher than, the ones of commercially available softwood products. Recommendations are also made in the paper on the appropriate capacity factors to be used for various service categories of structures. The proposed capacity factors were found to be 5% to 12% lower than the ones currently used in Australia for beams manufactured from mature softwood logs

Capacity and reliability of LVL beams manufactured from juvenile hardwood plantation logs

This paper summarises parts of the research outcomes of a university-government collaborative project aiming at determining the capacity and reliability of veneer-based structural products manufactured from early to midrotation (juvenile) hardwood plantations logs. Two species planted for solid timber end-products (Eucalyptus cloeziana and Corymbia citriodora) and one species traditionally grown for pulpwood (Eucalyptus globulus) were studied for the manufacture of the new products. Focus of this paper is on LVL beams. To cost-effectively determine the nominal design bending strengths of the new beams, a numerical model was developed. The model was found to accurately predict the strength of LVL beams with an average predicted to experimental ratio of 1.00 with a low coefficient of variation of 0.10. Using an established probabilistic database of the material properties of the veneered resources as model input, Monte-Carlo simulations were then performed. The design strength of the new LVL beams was established and found to be comparable to, and in some cases up to 2.5 times higher than, the ones of commercially available softwood products. Recommendations are also made in the paper on the appropriate capacity factors to be used for various service categories of structures. The proposed capacity factors were found to be 5% to 12% lower than the ones currently used in Australia for beams manufactured from mature softwood logs

Impact of Facility Location on the Financial Performance of Integrated and Distributed LVL Production in Subtropical Eastern Australia

In subtropical eastern Australia, the declining availability of traditional, large hardwood native forest logs has motivated hardwood sawmills to explore potentially utilising small logs in the manufacture of veneer-based engineered wood products (EWPs), such as laminated veneer lumber (LVL). An aspatial mathematical model that maximises net present value (NPV) over a 30-year project life has been applied to estimate the financial performance of LVL manufacture in this region. Of particular interest was how facility location affected financial performance, and whether distributed production of veneer (close to the log resource) and LVL (distant from the log resource) may be more profitable than integrated production under some circumstances. While integrated production of veneer and LVL near the resource maximised NPV, distributed production was found to be more profitable than integrated production in situations where the LVL manufacturing facility had to be located relatively far from the resource. Nevertheless, the level of value-adding and processing scale had a greater impact on financial performance than facility location. The analysis also highlighted that log procurement strategy substantially affected financial performance. Encouragingly for forest growers and wood processors, utilising large volumes of small diameter logs, was important for maximisation of NPV of larger-scale LVL facilities

Barriers to the Effective Adhesion of High-Density Hardwood Timbers for Glue-Laminated Beams in Australia

A number of international timbers of high commercial importance are extremely difficult to glue, which is significantly hindering access to global market opportunities for engineered wood products, especially for heavily demanded structural products. Some particularly problematic timbers in Australia are the dominant commercial hardwood species, including spotted gum (Corymbia spp.) and Darwin stringybark (Eucalyptus tetrodonta). These species are renowned for their very high mechanical properties, natural durability and attractive aesthetic appeal. However, they are notoriously difficult to glue, especially for sawn laminate-based engineered wood products, such as structural glue-laminated beams. Despite considerable effort and testing of diverse internationally established best-practice approaches to improve adhesion, glue-laminated beam samples of these timbers still frequently fail to meet the requirements of the relevant standard, mainly due to excessive glue line delamination. This paper discusses the key barriers to effective adhesion of these high-density timbers and particularly emphasises the necessity of achieving greater adhesive penetration. Greater adhesive penetration is required to enhance mechanical interlocking, entanglement and molecular interactions between the adhesive and the wood to achieve stronger and more durable bonds. Potential solutions to enhance adhesive penetration, as well as to improve gluability in general, are discussed in terms of their likelihood to satisfactorily prevent delamination and the potential to be applied at an industrial scale. This new fundamental understanding will assist the development of solutions, allowing industry to commercialise newly engineered wood products made from high-density timbers

Towards reducing the capital cost of manufacturing Laminated Veneer Lumbers: Investigating finger jointing solutions

The capital cost of setting up a Laminated Veneer Lumber (LVL) plant which produces continuous LVL billet products, through a continuous veneer assembly and hot-pressing processes, is significant. However, the utilisation of batch-type presses, similar to those employed in the plywood industry, could significantly reduce this initial cost and may provide new opportunities for small to medium scale operations. This process would produce shorter billet lengths which would need to be joined together to produce lengths viable for structural products. Scarf joints have been used commercially to join some veneer-based engineered wood products but have limitations, while finger joints are a common method for jointing sawn timber products and offer some key advantages but is not a common method to join veneer-based products. Consequently, this paper focusses on investigating the influence of key manufacturing parameters on the performance of finger jointed LVL. The effect of the joint orientation (horizontal or vertical), the finger length, the gluing pressure and the adhesive type on the joint strength and stiffness were investigated. The finger jointed LVL were tested in edge bending, flat bending and tension, and the results were compared to reference unjointed LVL. The bending performance of the finger jointed LVL was also compared to scarfed jointed LVL. In total 304 tests were performed. The results indicated that the average strength values of finger jointed LVL can reach up to 99% of the average strength of unjointed LVL and compares to scarf jointed LVL on flat bending. Horizontal joints, being more practical to produce for deep beams, performed similarly to vertical joints. The 25 mm joints were found to have no mechanical advantages over the 20 mm investigated finger joints. A gluing pressure lower than the Eurocode's recommended level for solid timber achieved sufficient bonding for the products to be utilised. The gluing pressure was also found not to influence the performance of the joint, for the range of pressures investigated. Both polyurethane and resorcinol-formaldehyde adhesives produced high performing products, with the latter displaying superior adhesive bond durability. The paper concludes that finger jointing LVL represents a viable solution to manufacture usable LVL lengths from short LVL billets, but have lower edge bending efficiency than scarf jointed LVL