Determining optimal primary sawing and ripping machine settings in the wood manufacturing chain

for wood manufacturers around the world, the single biggest cost factor is known to be its raw material. Maximum volume recovery of this raw material is, therefore, of key importance for the industry. The wood products industry consists of several interrelated manufacturing steps for converting trees into logs and logs into finished lumber. Each operation usually optimises its functionality in isolation from the preceding and following operations. It is a well documented fact that the optimisation of decisions through the whole chain of operations is considerably more profitable than the optimisation of individual operations. The objective of this study was to determine the optimal machine settings for two interrelated operations, namely the sawing and ripping operations which have tradition? ally been optimised individually. A model, having two decision variables, was developed which aims to satisfy market demand at a minimal cost. The first decision was how to saw the log supply into different thicknesses by choosing specific sawing patterns. The second was to decide on a rip saw's priority value settings, which determines how the products from the primary sawing operation are ripped into products of a certain thickness and width. The techniques used to determine the machine settings included static simulation with the SIMSAW software to represent the sawing operation and mixed integer programming to model the ripping operation. A metaheuristic, namely the Population Based Incremental Learning algorithm, was used to link the simulation and mixed integer models and to determine the optimal settings for the combined process. The model's objective function was to minimise the cost of production. This cost included the raw material waste cost and the over or under production cost. The over production cost included the stock keeping costs and the under production cost was estimated as the buy?in cost of under supplied products from another wood supplier. The model performed well against current decision software available, namely the Sawmill Production Planning System package, which combines simulation and mixed integer programming techniques to maximise profit. The model added further value by modelling and determining the ripping priority settings in addition to the primary sawing patterns.     

Integrated harvesting for conventional log and energy wood assortments: a case study in a pine plantation in Western Australia

Biomass or energy wood harvesting can be integrated with conventional log harvesting (saw log or pulpwood production) to allow more cost-effective energy wood supply. The efficiency of an integrated energy wood harvesting system was evaluated and compared with conventional log harvesting in a 32-year-old Pinus radiata plantation (radiata pine) located in south-west Western Australia. The harvesting system consisted of a harvester and a forwarder. The study included two treatments: a conventional log-harvesting operation where merchantable sawlogs and pulp logs were produced at the stump by the harvester and extracted by the forwarder; and an integrated energy wood operation where the harvester produced sawlogs, pulp logs and energy wood at the stump that were extracted by the forwarder. In the integrated energy wood harvesting plot, 37 m3 ha?1 of energy wood was extracted in addition to the sawlog and pulp log volumes. Extracting the additional energy wood reduced the productivity of the forwarder and increased the cost of extraction (AU$2.7?m?3) compared with the control plot (AU$2.2?m?3). Harvesting system cost was not significantly impacted, with a cost of AU$3.18?m?3 in the control plot and AU$3.23?m?3 in the integrated energy wood harvesting plot. Diameter at breast height (DBH) was a significant factor influencing the working time of the harvester, whereas load volume, extraction distance and extraction type (sawlog, pulp logs, and pulp log/energy wood) significantly impacted forwarding time. Increasing DBH resulted in longer working cycles for the harvester. Heavier loads and longer forwarding distances increased forwarding cycle time, while extracting sawlogs was least expensive and energy wood extraction was the most expensive. The marginal cost of the energy wood was approximately AU$10.2?m?3 (AU$7.0 extraction and AU$3.2 harvesting), which is about double the cost of the sawlogs. Additional material recovered in the integrated energy wood plot resulted in less residual residues on the plot (103.2 green metric tonnes per hectare [GMt ha?1]) than the control plot (144.2 GMt ha?1).     

A method for under-bark detection of the wood grain angle radial dependence

Abstract

Twist in wood, being closely related to spiral grain, may cause serious problems in building structures, furniture and joinery. It is therefore of great interest to sort out, at an early stage in the manufacturing process, trees, logs and boards that have an excess of spiral grain. The spiral grain pattern is described by a helical deviation of the fibre direction in relation to the longitudinal direction of a living tree or a log and seems to be an indicator for other defects such as compression wood. Remote microwave sensing of spiral grain has received a lot of interest during the past two decades. Its development has been impeded by the large variation with moisture content of the microwave properties of wood and by the complexity in modelling the electromagnetic field in a log with spiral grain. A review is presented of a direct method with no requirement for information on moisture content for boards. This procedure has recently been generalized to cylindrical logs and trees having a constant slope of the grain. A further generalization is presented here to allow for the normal spiral grain pattern with radially changing slope of grain in wood under bark. Based on this theory, a measurement procedure is proposed for the detection of wood grain angle with radial dependence, requiring no information on moisture content in the sapwood, which is also applicable to completely or partially frozen wood. A suitable application would be an instrument to use in the forest for measurements on living trees or logs.     

日本的木材流通

日本木材流通的特点是: 国产材的开发利用与进口外材并举。60年代后, 进口材在总需材量中所占比重越来越大; 原木在总进口材中所占比重越来越小。这是当前日本林业生产、木材加工和流通领域所面临的新问题。     

国外胶合板生产发展趋向和我国的对策

随着适宜于制造胶合板的木材供应减少和价格上升,胶合板生产的优势地位已受到相当大的影响。小径材或速生材的利用及胶合板用材树种的扩大是发展胶合板生产最重要的措施。变革胶合板生产工艺可以开发利用新的原料来源、提高劳动生产率、降低生产成本、并使产品多样化。计算机控制和先进的电子技术大大地提高了胶合板生产线的效率和功能,并保证了产品的质量。     

Influence of Log Characteristics on Drum Debarking of Pulpwood

Properties of 200 poorly debarked softwood logs were studied in order to examine how different log characteristics affect drum debarking of mixed pine (Pinus sylvestris L.) and spruce [Picea abies (L.) Karst] pulpwood during the summer. The definition of a poorly debarked log and the sampling criterion was that >10 dm² bark remained on the log surface. The average share of poorly debarked logs was 8% and the most frequent log type was breakage logs. The main species among the poorly debarked logs was spruce and the mean wood moisture content was considerably lower than for the pulpwood chips. Many logs were affected by root rot or were damaged by harvesting equipment, resulting in reduced moisture content and, consequently, in increased bark/wood shear strength. Bark from the poorly debarked logs contributed to approximately 68% of the bark content in the chips. By avoiding air-drying of pulpwood, or by sorting pulpwood prior to debarking, the bark content in chips might be substantially reduced, which would improve the purity of the pulp and decrease production costs.     

Combined production of sawn timber and firewood billets at a birch sawmill in Finland: A simulation approach

Abstract

Growing markets for chopped firewood have created alternative uses for the by-products of sawmills. Based on empirical data and simulated results, the potential of birch (Betula pendula Roth, Betula pubescens Ehrh.) from commercial thinnings for combined industrial production of sawn timber and firewood billets was investigated. In the simulations, different sawing patterns were used for logs intended to combine production of sawn timber and billets for chopped firewood (‘sawlogs’), and for logs intended only to firewood production (‘firewood logs’). Finally, economical feasibility analysis was done concerning the differences between the sawmills’ traditional business concept and the novel concept combining sawn wood and firewood production. The bucking results for the volume yield of different timber assortments varied only slightly between the different bucking options, i.e. the combinations of timber assortments. The main differences in the volumes of timber assortments were due to the stand type where the birch trees were sampled (planted, naturally regenerated, mixed birch–spruce). In the sawing procedure, the output of sawn timber varied between 24% and 42% of the log volume in the sawlogs, depending on the log diameter class. As the volume yield of sawn timber and firewood billets was counted together in the case of sawlogs, the log consumption was c. 1.75 m³ of roundwood per 1 m³ of sawn timber and firewood billets. In the case of the firewood logs, the log consumption rate was considerably lower, only c. 1.35. The economic calculations showed that using the firewood approach in sawing may increase the net added value of products by €1.9–5.4 m^?3 of logs, depending on their diameter class. As a conclusion, parallel production of sawn timber and firewood from logs from the first and second commercial thinning of birch-dominated stands is a concept that could work as an alliance between a sawmiller and a firewood entrepreneur. The concept could be competitive compared with both traditional sawmilling and production of chopped firewood.     

Yield and mechanical properties of veneer from Brachystegia nigerica

In an effort to find suitable wood from natural forest to meet the demand for veneer products, the yield and tensile strength of veneers produced from Brachystegia nigerica were investigated. Two trees of B. nigerica were separately selected from 10 different natural forest zones while two logs were obtained from each tree. The logs were debarked and steamed in a vat prior to rotary peeling and slicing for veneer production. The optimum steam temperature was determined by considering different temperatures: 50°C, 60°C, 70°C, 80°C and 90°C for 24 h. Thereafter, optimum steam time was determined at the optimum temperature by considering durations of 24, 48, 72 and 96 h. The average taper of 0.75 mm per 1.0 m length was recorded for B. nigerica, indicating that the logs were reasonably cylindrical; thereby its logs are good for the production of veneer. The yield ranged from 44% to 61% with an average of 52% of the log input. The tensile strength of the veneer was tested perpendicular to grain and both peeled and sliced veneers had the highest tensile strength between 70°C and 90°C, suggesting that softening of wood polymers, especially lignin, is between 70°C and 90°C. The optimum temperature and time for veneer production are 70°C and 48 h, respectively. Commercial production of veneer from B. nigerica is feasible based on the yield and mechanical properties of the obtained veneer, thereby encouraging the expansion of the scope ofits utilization.     

空心胶合木柱轴心受压性能研究

【目的】节能环保理念越来越受关注,木材作为绿色环保的可再生建筑材料可应用在工程中,目前国内木建筑中应用的木柱主要局限于原木圆柱,为了提高木材利用率,同时降低成本,改善受力性能,满足工程需要,提出一种新型的空心胶合木柱,并进行试验研究分析。【方法】使用相同尺寸拱形锯材作为骨架,利用环氧树脂胶粘剂进行胶合,制作3根空心胶合木柱试件进行轴心加载受压试验,研究空心胶合木柱的轴压力学性能,在试验过程中通过仪器记录应变、应力和位移等数据,主要分析木柱的竖向与横向应变、竖向与侧向位移、稳定承载力等特性,并利用ABAQUS有限元软件进行建模对比分析,探讨木柱最终破坏特征。【结果】空心胶合木柱破坏形态主要是整体压屈破坏,达到极限荷载80%左右时,承载能力快速下降,侧向位移随荷载增加而迅速增大,加载过程中存在多个增长台阶;与同截面积原木圆柱比较,理论承载力提高了4.3%,计算得承载能力稳定系数为0.9,材料缺陷对轴心承载力有影响;通过有限元建模分析,材料在弹性阶段理论值与试验值吻合程度较好。【结论】空心胶合木柱应用在实际工程中是可行的,能够满足工程使用需求,充分利用小型锯材,提高了木材利用率,降低了成本,相较于原木圆柱受力性能更好。     

Simulation of the yield of knot-free components from Scots pine (Pinus sylvestris L.): A comparative study of star-sawing and square-sawing

Abstract

The production of knot-free wood is important since the market demands wood without knots for reasons of both appearance and material properties. This work describes a simulation of the removal of knots from star-sawn and square-sawn timber. The efficiency of the two methods is compared in terms of the length of the knot-free components obtained and the volume yield. The simulation was based on data for trees and logs taken from the Swedish Stem Bank. These data were then used to simulate the sawmill process in a computer program called the Virtual Sawmill. Data related to the boards obtained were used in a MATLAB model simulating the cross-cutting of knots. Simulated star-sawing of logs with a top diameter exceeding 230 mm gave a mean knot-free component length of 417±321 mm, while the mean length of knot-free components for simulated square-sawing of the same logs was 298±122 mm. The volume yield of knot-free components from the two sawing patterns was 91% for star-sawing and 87% for square-sawing. For timber with cross-section dimensions of 38×75 mm², the mean length and yield of knot-free components from simulated star-sawing were 451±349 mm and 90%, respectively. In simulated square-sawing, the corresponding values were 263±197 mm and 82%, respectively. This shows that star-sawing has potential for the production of knot-free timber.     

Optimization potential for perception-oriented appearance classification by simulated sawing of computed tomography-scanned logs of Norway spruce

Abstract

Wood, as a natural material, has favourable properties in both technical and aesthetic aspects. Due to its inherent variability, production of high-quality sawn timber demands adequate control of log conversion, which is feasible with computed tomography (CT) log scanning. Existing appearance grading rules for sawn timber might not fully reflect people's visual perception of wood surfaces, and therefore, an alternative, more perception-oriented appearance classification could be beneficial. An appearance classification of sawn timber based on partial least squares discriminant analysis (PLS-DA) of knot-pattern variables was developed and tested. Knot-pattern variables derived from images of board faces were used in training PLS-DA models against an initial classification of the board faces previously established by aid of cluster analysis. Virtual board faces obtained from simulated breakdown of 57 CT-scanned Norway spruce logs were graded according to the developed classification. Visual assessment of the grading results indicated that the classification was largely consistent with human perception of board appearance. An initial estimation of the potential to optimize log rotation, based on CT data, for the established appearance grades was derived from the simulations. Considerable potential to increase the yield of a desired appearance grade, compared to conventional log positioning, was observed.     

The Fingerprint Method: Using Over-bark and Under-bark Log Measurement Data Generated by Three-dimensional Log Scanners in Combination with Radiofrequency Identification Tags to Achieve Traceability in the Log Yard at the Sawmill

In the forestry–wood chain the concept and the technologies of traceability are in a mature development phase. Important advances in marking and reading techniques have been made in different parts along the forestry–wood chain. For Swedish sawmills the most critical information gap is located between the log sorting station and the saw intake, where the forest log batch identity disappears and the logs are mixed according to different sorting criteria. This study utilizes radiofrequency identification tags for automatic log marking/reading to develop a traceability system for logs, which is free of marking/reading, between the log sorting station and the saw intake, i.e. the fingerprint method. The originality of the fingerprint approach rests on the hypothesis that logs are separate entities with individual features. The results show that the log parameters and the search algorithm developed, combined with the negative influence of the measurement uncertainty due to bark thickness and bark damage, made it possible to achieve an individual separation for 57% of the tested logs.     

中国的木材工业与国民经济的可持续发展

用大量的事例和数据论述了建国50多年来,特别是改革开放后的20多年,在我国的国民经济发展的同时,钢材、水泥两大原材料的生产也同步快速增长。由于我国森林资源短缺,木材的生产量却呈现了负增长。但是,由于同期快速发展的木材工业,大大提高了中国的木材利用水平,降低了木材消耗;利用部分木材、采伐和加工剩余物及多种非木质材料制造人造板,成为世界第二大人造板生产国;进口部分原木和锯材作为补充,这三种措施的综合结果,每年可为我国经济发展带来近2亿m3木材的实际效益,技术进步和发达的木材工业为国民经济可持续发展提供了技术支撑。     

Sawing patterns for large-diameter sugi (Cryptomeria japonica D. Don) sawlogs: Current status and future outlook

Abstract

A survey was conducted at nine sawmills in Japan to evaluate and compare the sawing of sugi (Cryptomeria japonica D. Don) logs of 30 cm and more in diameter. The purpose was fourfold: (1) to document sawing patterns appropriate to the large-diameter logs; (2) to examine the composition of wood components (structural, nonstructural, and fixtures) produced from those patterns; (3) to investigate log and product prices; and (4) to ascertain distances to the log supplier and product markets. Impetus for the study arose from a forecasted shift in the diameter distribution of plantation trees in Japan; from small and medium-sized logs to large-diameter logs. With an overabundance of large-diameter domestic logs forecasted within the next decade, the need to understand how to best utilize and effectively process the large-diameter resource is of utmost importance.     

Stress-wave velocity of trees and dynamic Young’s modulus of logs of 4-year-old Eucalyptus camaldulensis trees selected for pulpwood production in Thailand

Eucalyptus camaldulensis Dehnh. is extensively planted in Thailand to produce wood chips used as raw material for pulp and paper. To promote the utilization of the wood from plantation-grown E. camaldulensis for solid lumber, stress-wave velocity of trees and dynamic Young’s modulus of logs were investigated for 4-year-old trees of eight half-sib families selected for pulpwood production on the basis of the growth characteristics in the previous tree breeding program. For the eight families, the mean stem diameter at 1.3 m above ground level and mean tree height were 7.6 cm and 11.9 m, respectively. The mean stress-wave velocity of eight families was 3.45 km/s. Dynamic Young’s modulus of logs ranged from 7.88 to 17.64 GPa, and the mean value for the eight families was 11.72 GPa. Stress-wave velocity of trees was significantly correlated with dynamic Young’s modulus of logs, suggesting that dynamic Young’s modulus of wood can be evaluated nondestructively by stress-wave velocity of trees. Significant differences in stress-wave velocity and dynamic Young’s modulus of logs were obtained among families. Thus, to promote the utilization of E. camaldulensis wood for solid lumber production, selection of trees with high Young’s modulus should be applied to trees already selected for the growth characteristics in the previous tree breeding program.     

吉林省实木产品生产中的木材损失研究

锯切用原木加工利用过程中,实木产品是主要产品,因此,提高原木到实木产品成本(原木价格占总生产成本的60%以上),增强木业企业市场竞争能力,改善目前经济效益状况皆有重要意义。1　吉林省原木到实木产品木材利用率概况吉林省木业企业锯切用原木径级一般为18ｃｍ～30ｃｍ,平均直径为26ｃｍ,平均长度4ｍ,2等以下原木居多。主要实木产品有实木地板,复合木地板,实木门,指接木门框,集成材,百叶窗等。具有一定规模的企业平均木材利用率为实木地板234%(13个厂家平均值),实木家具18%(7个厂家平均值),复合木地板(柞木,色木,桦木)105%(7个厂家平均值),…     

Classification of Picea abies Pulpwood According to Wood and Stand Properties

Different classification systems for Norway spruce (Picea abies (L.) Karst.) pulpwood were compared. The classification systems were applied on truckloads or single logs in southern Sweden. Truckload classification according to mean annual growth ring width gave better separation of the wood properties basic density, juvenile wood and dry matter content, than classification according to harvest type (first thinning, later thinning or final felling). The assortments did not have significantly different wood brightness. Sorting at log level according to diameter, mean annual growth ring width or number of annual growth rings, which could be done at harvesting, did not drastically improve differentiation of the mean values of the wood properties or reduce variance compared to truckload classification. The variation in wood properties within assortments remained large owing to the large variation in wood properties between and within logs. Substantial reduction in dry matter variation could be achieved by truckload classification during the summer.     

新世纪我国木材科学与技术展望

在新世纪到来之际，为了适应全球经济一体化，科技经济一体化以及国家经济体制改革和科技体制改革的发展要求，我国将加强木材科学与技术的知识创新和技术创新，对学科发展进行重大调整，知识创新将以人工林木材为主的植物材料的材质材性与生物形成和加工利用的关系方向有重大进展；技术创新将以企业为主，在以木材为主的植物资源加工利用技术，产品增值加工技术，木质材料性能，产品应用技术和环保技术方面有较大的突破，木材科学与技术学科的发展特点将更显交叉性和边缘性，向植物材料学，木基复合材料学，木质重组材料学，木质环境材料学，木结构环境工程学和木材化学和加工学等方面6发展。     

“一带一路”沿线国家对华原木出口贸易效率与潜力

利用"一带一路"沿线主要国家与中国双边原木贸易数据,文中实证分析影响沿线国家对华原木出口主要因素,并进一步测算出其原木出口贸易效率与潜力。结果表明:中国人造板和木家具出口量、沿线国家人均GDP、国土面积、与中国是否有共同边界、距离和经济规模相对差异等指标是影响对华原木出口的主要因素;2007年以后,沿线国家对华原木出口贸易效率逐年降低,年平均效率低于0.5,而原木出口贸易潜力则逐年提升。从保障我国原木贸易安全、降低原木进口成本以及加大对"一带一路"沿线国家林业投资等方面提出相应建议。     

Acoustic measurements on trees and logs: a review and analysis

Acoustic technologies have been well established as material evaluation tools in the past several decades, and their use has become widely accepted in the forest products industry for online quality control and products grading. Recent research developments on acoustic sensing technology offer further opportunities to evaluate standing trees and logs for general wood quality and intrinsic wood properties. Although the concept of using acoustic velocity as an effective measure of stiffness applies to both standing trees and felled logs, the method typically used to measure acoustic velocity in trees is different from that used in logs. Consequently, there is a significant difference in measured velocity values between trees and logs. Other factors affecting tree–log velocity relationships include tree diameter, stand age, operating temperature, and wood moisture content. This paper presents the fundamentals of acoustic wave propagation in trees and logs and discusses two different mechanisms of acoustic velocity measurement, time-of-flight for standing trees and resonance for logs. Experimental data from previous studies are reviewed and analyzed to examine the strength of the tree–log velocity relationships and discuss the factors that influence tree velocity deviation.