Lumber Manufacturing Research Articles

An Evaluation of Low-Grade Red Oak and Soft Maple as Raw Material for Cross-Laminated Timber Panel Production

Abstract Utilization of hardwoods in the manufacture of cross-laminated timber (CLT) faces many challenges, one of which is the selection of raw material that is both technically and economically feasible. From an economic perspective, it would make sense to choose species and grades that are both readily available and relatively competitive with softwood species currently used in CLT manufacturing. For the purposes of this study, lower grades (2A Common, 2B Common, 3A Common, and 3B Common) of red oak and soft maple were deemed appropriate in fitting this profile. All lumber was visually graded according to both National Hardwood Lumber Association (NHLA) and Northeastern Lumber Manufacturers Association (NeLMA) grading rules, as well as nondestructively tested through flatwise bending to determine modulus of elasticity (MOE). The yield distribution of each species and NHLA grade, by visual structural grade, were analyzed. The mechanical testing of each species was analyzed based on the minimum allowable MOE of 1.2 x 106 psi as required by ANSI/PRG-320. Mechanical testing resulted in much higher yields of acceptable CLT material than visual grading, for both species. A total net worth analysis was conducted to evaluate the value of NHLA graded lumber being processed into structurally graded lumber for both species and both grading methods. Finally, a procurement analysis was conducted to determine the volume of lumber required for both species, in order to achieve a fixed volume of CLT-ready lumber.

Application of Metaheuristics to Packing Formation Support Systems of Pre-Cut Lumber Factory

In recent years, wood has been considered as a building material from the perspective of SDGs. Pre-cut lumber is often used for wooden houses, including roofs, floors, and pillars. It is preprocessed into a certain shape for the joint parts and has joint brackets if necessary. The use of them has the advantages of shortening the construction period and reducing the construction cost. The number of pre-cut lumber production factories in Japan decreased from 757 in 2001 to 659 in 2011 and then increased to 730 in 2016. Compared with 2011, the number of factories with sales of <500 million yen in 2016 decreased by approximately 30%, while the number of factors with sales of ≥500 million yen increased by 80%, indicating a trend toward a larger scale [1]. Therefore, improving the productivity of these factories is imperative. We have been researching the conversion of factories into smart factories to improve the productivity of pre-cut lumber manufacturing company A. In this company, employees take 1.2 h to prepare packing plans every day, and the company faces the challenge of improving the efficiency of planning operations. Herein, we propose an algorithm using an iterative local search (ILS) with Or-opt (ILS + Or-opt) for packing formation support systems to improve the efficiency of planning operations. This algorithm has the following two features. First, it uses Or-opt to create a neighborhood for a local search. Second, uses exchange neighborhoods when repeating the ILS to achieve diversity in the search.

Evaluation of Low-Grade Yellow-Poplar (Liriodendron tulipifera) as Raw Material for Cross-Laminated Timber Panel Production

Abstract Utilization of low-grade yellow-poplar (Liriodendron tulipifera) lumber would provide for alternative structural lumber sources and promote the growth of cross-laminated timber (CLT) manufacturing facilities within the Appalachian Region. A significant amount of low-grade yellow-poplar lumber (i.e., National Hardwood Lumber Association [NHLA] No. 2A and Below Grade) is utilized for wood pallets. In practice, this material is not graded for structural purposes. Additionally, research on yellow-poplar for structural use has focused on grading lumber from a small population of selected logs, not by regrading NHLA lumber from manufacturing facilities. Therefore, the research's objective was to investigate the structural grades of a typical population of NHLA graded No. 2 and lower lumber and evaluate their potential to meet structural grades necessary for CLT panels. NHLA graded lumber was regraded and assigned to visual structural grades following Northeastern Lumber Manufacturers Association rules and evaluated for flatwise bending modulus of elasticity (MOEb) by nondestructive proof loading. The results of the study indicated that 54.6 percent of the boards possessed a minimal structural visual grade required for CLT panels according to American National Standards Institutes/The Engineered Wood Association (ANSI/APA) PRG 320-2019 (2020). Splits were the most common limiting defect that downgraded boards to nonstructural grades. Also, 96.6 percent of the boards evaluated had a MOEb above the required minimal board value of 1.2 ×106 psi (8,274 MPa) listed in ANSI/APA PRG 320-2019 (2020). The results of the study indicated that a majority of NHLA low-grade yellow-poplar, when regraded for structural purposes, meets or exceeds minimum lumber grade values necessary for use in CLT panel production.

COVID-19 impacts on U.S. lumber markets

The Covid-19 pandemic led to an unprecedented increase in the U.S. price of softwood lumber by more than 300%. The reasons for this increase have been attributed to constraints on supply caused by pandemic-induced labor shortages, and increased demand for lumber caused by a Covid-19 related boom in domestic real estate and home improvements. In this paper, we examine the effect that these factors might have had on the increase in prices and the related changes in the welfare of U.S. lumber manufacturers and downstream users of lumber. We examine three cases where the demand function shifts outwards: (1) the lumber supply function remains unchanged; (2) the U.S. lumber supply function and that of its trading partners shifts inwards; and (3) U.S. lumber producers restrict output at its pre-Covid level. Overall, we find that U.S. producers gained between $0.7 and $8.0 billion per quarter as a result of the pandemic, while downstream processors gained $639 million. We argue, however, that the ultimate consumer of the downstream products that require lumber as an input (housing construction, furniture) might well be worse off as surplus lost as a result of reduced expenditures on commodities and services restricted by Covid-19 are not quite recovered when spending switches to lumber-related commodities.

Incidence of domestic subsidies vs. export taxes: An equilibrium displacement model of log and lumber markets in Oregon

Governments have used policies such as taxes on the exports of unprocessed wood products and subsidies to domestic manufacturers to improve the competitiveness of domestic industries with the goal of supporting economic activities especially in rural areas. Newer motivations for policy interventions come in the form of climate change mitigation targets whereby improved forest management and increased use of wood products provide a long-term solution to enhance carbon sequestration. We compare three different policies in terms of their welfare incidence, impacts on economic activity and carbon storage. To analyze the policy scenarios, we extend an equilibrium displacement model to include subsidies and calibrate it to represent Oregon's harvesting and lumber manufacturing sectors. The three hypothetical policies we study are an ad valorem log export tax, an ad valorem input subsidy received by Oregon mills, and an ad valorem subsidy received by Oregon lumber consumers. Our results show that the three alternative policies differ in terms of their impacts on economic returns, employment, and carbon storage, and none of the policy alternatives is superior along all these dimensions.

Раскрой круглых сортиментов с ядровой гнилью на конструкционные пиломатериалы

Softwood lumber is widely used for the manufacture of load-bearing structures. However, the quality of round timber for lumber manufacturing has been deteriorating recently. The average diameter of round timber entering sawmills is constantly decreasing, and heart rot is common in large-diameter round timber. This is due to the fact that more and more conifers in the forest are being affected by heart rot. The rot infestation is related to the deterioration of the ecological situation caused by environmental pollution. As a rule, the removal of rot occurs at the stage of round timber harvesting. Therefore, during harvesting, most of the wood with heart rot continues to remain in the forest. In addition to littering the area, it continues to infect sound wood. At the same time, together with the wood affected by rot, the sound sapwood, which has good strength characteristics, is also removed. A method for processing round timber with heart rot into elements of load-bearing structures is proposed. In particular, a technological scheme for manufacturing I-beams from such timber has been developed for low-rise house construction. Corner elements are produced as a result of cutting round timber and removing heart rot by milling. The corner elements are dried in clamped state using special devices. Then they are glued together to obtain beams with a cross-section in the form of an I-beam. A set of equipment for the processing round timber with heart rot was selected. The paper presents the results of calculating the costs for organizing the production. The effectiveness of the technological project is evaluated using the method of discounted cashflows by the following indicators: net present value, profitability index, and discounted payback period. The assessment results confirm the effectiveness of the production organization of load-bearing structures made of round timber affected by heart rot. The processing of wood that remains in the forest into elements of building structures not only increases the wood reserves for construction, but also creates conditions for improving the ecological situation in forest areas. For citation: Toropov А.S., Byzov V.Е., Toropova Е.V., Sergeevichev А.V., Sazanova E.V. Cutting of Round Timber with Heart Rot to Structural Lumber. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 6, pp. 160–172. DOI: 10.37482/0536-1036-2021-6-160-172

Influence of torrefaction on the heating values and energy densities of hardwood and softwood

Lumber manufacturing facilities generate large amounts of wood residues as a by-product of processing. In this study, the torrefaction characteristics of the Cryptomeria japonica and Acacia confusa residues were evaluated and compared to microcrystalline cellulose. The torrefied products also were analyzed. The results showed that the higher heating value (HHV) of the C. japonica and A. confusa residues increased to 5,993 and 5,576 kcal/kg after 20 min of torrefaction at 310 °C, which was higher than the microcrystalline cellulose (4,340 kcal/kg). The energy densification of the torrefied biomass could rise to 1.17 to 1.20 times higher than the raw biomass. The condensable gaseous product was an organic acid liquid. The liquid product consisted of some alkanes, alcohols, esters, and amides. The exothermic temperature would be reduced after torrefaction. Additionally, the thermal treatment of the biomass destroyed the cellulose crystals and reduced the cellulose crystallinity index. In order to reduce the usage of fossil fuels, the torrefied solid biomass could be mixed with coal in power plants directly.

Domestic large-diameter log use in the Japanese lumber manufacturing industry: focusing on regional differences

ABSTRACT Japan’s postwar policies with respect to forestry management have led to the aging of planted forests and a shift toward large-diameter logs that has created a challenge for how to use such logs in the lumber manufacturing industry. In recent years, medium-diameter logs have been the predominant type, and there has been less demand for large-diameter logs. This study examines the Japanese lumber manufacturing industry’s consumption of domestic timber using survey data from 21 member companies of the Domestic Timber Sawmill Association. The results suggest that regional characteristics and the tree species consumed are the two main factors that drive the decision to use large-diameter logs. While current demand for large-diameter logs is considered low, the results show that demand is present, and there are signs of growing consumption of these logs within the lumber manufacturing industry. As the current machinery that handles medium-diameter logs depreciates, it is expected that companies will respond by either introducing machinery that can accommodate large-diameter logs or changing their products.

Cutting power and surface quality in sawing kiln-dried, green, and frozen hem-fir wood

The lumber manufacturing industry faces challenges due to the cutting of wood with a high variation in moisture content and temperature. In this study, the cutting power and waviness during the circular sawing process of kiln-dried, green, and frozen hem-fir wood were measured and compared under different feed and rotation speeds. An analysis of variance (ANOVA) was performed to evaluate the impact of cutting parameters and the wood condition (kiln-dried, green and frozen), and a decision tree regression model was developed to predict the cutting power and waviness. The ANOVA highlighted that the feed speed had the most impact on cutting power, followed by the wood condition. Similar results were obtained from the decision tree regression (R2 = 0.89). The developed model failed to accurately predict the waviness from the cutting parameters, which emphasized the need for online wood sawing monitoring systems and a deeper understanding of saw blade’s dynamic behavior. The role of moisture content in the cutting power and waviness was nonlinear. The highest cutting power corresponded to sawing frozen wood, while there was no significant difference between sawing dry and green wood. The largest values of waviness were associated with sawing of dry wood, whereas sawing frozen and green wood yielded similar waviness. Sawing at higher rotation speeds yielded an increase in the cutting power but improved the surface quality by lowering the waviness.

Sensor fusion and random forest modeling for identifying frozen and green wood during lumber manufacturing

The sawmilling industry faces challenges in winter due to cutting frozen logs. This study proposes a methodology using sensor fusion and random forest modeling to differentiate frozen and green wood using sensory features acquired during the wood sawing. The process was monitored with power, sound, vibration and acoustic emission (AE) sensors, and different sensory features were extracted to develop random forest models. The vibration sensor showed superior monitoring performance and combined with sound and AE sensors, maximum accuracy (93%) was achieved. The model could accurately identify frozen wood in lumber manufacturing, which can be used to adjust the cutting process.

Models for predicting the within-tree and regional variation of tracheid length and width for plantation loblolly pine

AbstractLoblolly pine is a major fibre source for the pulp and paper industry. Here we developed the first nonlinear models to predict the within-tree and regional variation of tracheid length and width for planted loblolly pine. Data were obtained from macerated tracheids and near-infrared spectroscopy calibration models from trees sampled in 109 stands across the southeastern United States. The fixed effects for the final tracheid length model, which included cambial age, height of disk within tree, and physiographic region, explained 71 percent of the variation with root mean square error (RMSE) of 0.28 mm, while the fixed effects for the final tracheid width model explained 57 percent of the variation with RMSE of 1.4 μm. There was significant variation in tracheid properties across the growing regions. Tree maps showing within-tree variability in tracheid properties were produced. Five simulated scenarios were compared using the models developed, with mean tracheid dimensions calculated on a whole-tree basis at a first and second thinnings, and at final harvest. Also from the final harvest, the tops of trees, and outerwood chips produced during lumber manufacturing were also simulated. For the whole tree scenarios, both mean tracheid length and width increased with age, increasing from 2.24 mm and 40.5 μm (age 12), to 2.51 mm and 41.3 μm (age 18), and to 2.73 and 41.8 μm at age 25, respectively. The tops of the trees at age 25 had a mean tracheid length of 2.46 mm and a mean width of 41.0 μm, while the chips had a mean tracheid length of 3.13 mm and a mean width of 42.5 μm. Due to the models representing samples collected from across the southeastern United States, and their relatively high precision, they are suitable for incorporation into growth and yield systems allowing for prediction of tracheid properties.

Intelligent wood machining monitoring using vibration signals combined with self-organizing maps for automatic feature selection

Data-driven models were developed for monitoring the power consumption and wood quality during the lumber manufacturing process. The study proposes hybrid models using vibration signals combined with self-organizing maps (SOMs) for cutting power and waviness prediction in the circular sawing process of Douglas-fir wood under very high feed speed conditions. The acquired vibration signals were fed into SOMs with different topologies for data mapping and automatic sensory feature selection, which were fed into the adaptive neuro-fuzzy inference system (ANFIS) or multilayer perceptron (MLP) neural network (NN) for cutting power and waviness prediction. The monitoring performance of the hybrid SOM-MLP NN and SOM-ANFIS models was compared. The frequency response of vibration signals and its correlation with the cutting parameters as well as the cutting power and waviness were discussed. The study shows that the developed SOM models to select the optimal features from the vibration signals could accurately predict cutting power and waviness when combined with a machine learning model. The prediction performance is highly dependent on the optimal choice of SOM topology. Having a poor choice of SOM topology, fine-tuning the architecture of ANFIS and MLP NN is crucial and greatly impacts the monitoring performance. Based on the obtained results, SOM is recommended for the automatic feature in the machining or tool condition monitoring, where due to process high variability, manual feature selection is a challenging task. SOM combined with an ANN or ANFIS makes a powerful intelligent model for monitoring complex processes such as wood circular sawing.

Effect of growth stress and interlocked grain on splitting of seven different hybrid clones ofEucalyptus grandis×Eucalyptus urophyllawood

AbstractTrees with high levels of growth stress begin to show log end splits (LES) immediately after harvesting, usually reaching its maximum end split in a week, and these tensions also create splits during lumber manufacturing. Interlocked grain is another characteristic that impacts the properties of eucalyptus wood. The aim of this study was to evaluate the effect of growth stress and interlocked grain patterns on log end splitting of seven different hybrid clones ofEucalyptus grandis × Eucalyptus urophyllaplanted in Brazil. The growth stress indicator (GSI) was measured in standing trees before harvesting. Splits were measured on logs in three different stages, and interlocked grain from wood blocks was obtained across the center of the cross-section. The results showed that LES occurred as soon as the trees were harvested; however, for better selection of clones, LES should be evaluated after a week of harvesting. There were statistically significant correlations for GSI with LES. Clones that presented higher values of interlocked grain tended to develop lower values of GSI and LES. Using GSI and interlocked grain measurements, it was possible to select the most indicated eucalyptus clones for lumber production.

Drying operation planning in a sawmill

The success of lumber manufacturing lies on the ability to maintain the quality of the wood along the production process. The drying stage in a sawmill is one of the more important steps in the lumber production, since wood value and characteristics required by customers depend on this process phase. In a sawmill, a set of drying kilns operating in parallel out of phase is available, and periodically, packages of boards enter to this drying sector in order to be processed. Drying kilns are filled with wagons loaded with packages of boards. Different operative conditions must be satisfied in order to assure an efficient processing. These tasks involve several decisions, which are addressed through a Generalized Disjunctive Programming model, and solved using the corresponding Mixed Integer Programming reformulation considering different objective functions. From the examples, two scenarios are assessed and the capabilities of the presented approach are highlighted.

A module to simulate the impact of western gall rust (Cronartium harknessii) on merchantable volume and lumber yields for lodgepole pine (Pinus contorta var. latifolia) stands in British Columbia

Western gall rust (Cronartium harknessii (J.P. Moore) E. Meinecke) is a pathogen that affects lodgepole pine (Pinus contorta Douglas ex Loudon var. latifolia Engelm. ex S. Watson) and has the potential to reduce lumber product yields derived from stands managed for the commercial production of timber. A dataset containing repeated measurements from 7775 trees located within the province of British Columbia, Canada, was used to develop equations that predict annual rates of stem infection, post-infection mortality, and the location of large stem galls. Results showed that annual rates of infection peaked between 3 and 5 years following stand establishment. Few new infections were predicted to occur beyond the stand age of 15 years. For an individual tree, the probability of first infection increased as its height increased relative to stand top height. The rate of mortality increased with the number of stem infections and was highest among trees infected within the first 3 years following planting. Mortality rates decreased thereafter, with many trees likely to survive to rotation. The equations predicting rust incidence and mortality were added to the Tree and Stand Simulator (TASS), an individual-tree growth model used within the province. A final equation predicting the location of large galls was added and allows TASS to account for losses due to the removal of stem defects during lumber manufacturing.

Validation of automated hardwood lumber grading system

Grading is one of the most vital steps in the hardwood lumber manufacturing process. For over one hundred years, hardwood lumber in North America has been graded by specially trained lumber inspectors using the National Hardwood Lumber Association (NHLA) Rules for the Inspection of Hardwood Lumber. With technology improving over time, the status quo of lumber grading is again being challenged. This paper outlines an automated lumber grading study using a Microtec Goldeneye 300 Multi-Sensor Quality Scanner™. The scanner is equipped with color cameras, dot-grid and profile lasers and an x-ray sensor to locate and classify defects at a speed of 980 linear feet per minute. The material studied was rough, kiln dried hardwood lumber of nine different commercial species. Over 1000 boards from each species were graded with the scanner and verified by a NHLA-trained human lumber inspector. This paper reviews the performance of the scanner and highlights its accuracy by species and individual grades within that species. Across the entire volume of boards scanned, the automated grading system was 99.50% on-value and 92.22% on-grade accurate.

A Comparative Life-Cycle Assessment of Briquetting Logging Residues and Lumber Manufacturing Coproducts in Western United States

Abstract. Timber harvest activities in the western United States have resulted in large volumes of low- to no-value logging (forest) residues. Alternatives to pile-and-burning are needed to best utilize this material and to mitigate the resultant environmental impacts. Briquetting (densifying) forest residues near-woods is one such option and is the focus of this study. This study presents a cradle-to-grave life-cycle assessment (LCA) performed to evaluate the overall environmental impacts associated with briquetting post-harvest forest residues and dry sawmill residues (sawdust) in the Pacific Northwest (PNW) region of the United States. Environmental impacts resulting from the two briquette production systems were compared with firewood and propane production, which are common residential heating sources in rural areas of the PNW, on a per 1 MJ of useful energy for domestic heating. In the briquetted post-harvest forest residue system, the feedstock preparation stage had the largest share in global warming (GW) impact, mainly resulting from the drying process (69.5%), followed by transportation. Valorization of post-harvest forest residues, in combination with a briquetter, to produce a bioenergy carrier was revealed to be advantageous in smog, acidification, and eutrophication impact categories, with considerable environmental benefits from avoided pile-and-burn emissions. With all scenarios investigated, briquette production from post-harvest forest residues with high dryer efficiency showed lowest GW impact compared to briquetting sawmill residues and firewood supply chain. For a scenario analysis, LCA showed that using a diesel generator to support the forest residue briquetter operation resulted in 45% higher GW impact compared to use of a wood-gas-powered generator. Keywords: Bioenergy, Biomass densification, Briquette, Forest residues, Life-cycle assessment, Sawdust.

The development of moisture and strain profiles during predrying of Eucalyptus nitens

ABSTRACTThis article describes one of a series of studies carried out at the University of Bio-Bio in Chile with the objective of characterizing the response of Eucalyptus nitens to drying. The ultimate goal is to minimize collapse and internal intra-ring checking in the industrial drying of Eucalyptus nitens, which currently prevents the lumber manufacturing industry in Chile from producing a large number of commercial solid wood products from this species. This study focuses, however, on the drying conditions that have been shown in previous studies and are known in the industry to minimize collapse and internal intra-ring checking. For these conditions, this study reports the development of moisture content and internal strain profiles during drying. In addition, a simple diffusion model based on the concept of effective diffusion coefficient was proposed to compare the drying rates in the radial and tangential directions. The results showed that the diffusion coefficient in the radial direction was approximately 50% higher than that in the tangential direction. Internal strains, on the other hand, developed approximately at the same time, regardless of the annual ring orientation. This indicates that it would be feasible to apply strain relief strategies simultaneously to all boards regardless of their annual ring orientation in order avoid internal intra-ring checking during predrying. This finding could be used as a benchmarking tool in the industrial drying for solid wood products of Eucalyptus nitens.

Collapse of Eucalyptus nitens Wood After Drying Depending on the Radial Location Within the Stem

Collapse is almost certain to occur in the industrial drying of Eucalyptus nitens and, as such this prevents the lumber manufacturing industry in Chile from producing commercial solid wood products from this species. This problem is still unsolved, and different studies to reduce collapse are currently underway. In this exploratory study, shrinkage and collapse after drying of Eucalyptus nitens was measured for boards cut from different radial locations within the stem (core, transition, and outer wood from pith to bark) and having different annual ring orientations (flat-sawn and quarter-sawn). Though exploratory, the results appear to confirm that pieces that were cut from the center of the trees were less susceptible to collapse than pieces cut from the transition zone between the center and the periphery. On average, collapse in transition wood was approximately 50% higher than the collapse observed in wood cut from the central zone of the trees.

Can Montana Participate in the Lumber Export Market to China?

Abstract The severe recession and the housing and lumber market collapse in the 2007 to 2011 period has led to increased interest in market diversification in an attempt to cushion the impact of market swings in the United States. An international market diversification strategy has been implemented by several lumber manufacturers in Oregon and Washington that allowed them to be well positioned to shift sales to the Asian market during this domestic lumber market collapse. By diversifying a portion of sales into new international markets, Montana sawmills may be able to stabilize demand for their products instead of being subject to domestic market demand swings. To determine if Montana sawmills can participate in the Chinese export market and to identify the best export opportunities, a strategic assessment was conducted through the use of a SWOT (strengths, weaknesses, opportunities, threats) analysis. For this process, Montana's lumber industry core competencies were identified and aligned with Chinese wood product demand to highlight potential export opportunities for the Montana sawmill industry. It was found that the optimal export opportunity consisted of dimension lumber from Douglas-fir (Pseudotsuga menziesii), lodgepole pine (Pinus contorta), and ponderosa pine (Pinus ponderosa) species with nominal 2 by 4 dimensions and with No. 3 utility and No. 4 economy product grades. This product mix provided the best fit with Montana's timber supply, manufacturing capabilities, and Chinese product demand. By incorporating this strategy with the help of international lumber brokers and experienced exporters, Montana sawmills will be well positioned to respond to domestic market fluctuations and future Chinese product demand opportunities.