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下锯法对落叶松规格材出材率及质量的影响 总被引：2，自引：2，他引：0
分别采用毛板下锯法(SDR技术)和四面下锯法,进行兴安落叶松规格材锯解加工的试验研究.结果表明,四面下锯法加工规格材的出材率较高,且高等级规格材的得率亦高.通过分析对比两种下锯法加工规格材的优缺点,为规格材的工业化锯解加工提供技术依据. 相似文献
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我省年产原木50万m~3,锯材约17万m~3。在资源不足,原木径级逐年缩小的情况下,要最大限度利用有限的木材资源,就必须提高出材率。根据基本原理和我省生产实践经验,下列有关提高出材率的因素,可供制材部门参考。一、小头进锯:进大带锯,采用小头向前。易看清径级、形状、缺陷,便于桉料下 相似文献
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速生人工林桉树原木生长应力大、径级较小,在锯解过程中易产生端裂和翘曲,在干燥过程中容易出现皱缩、开裂等缺陷,同时,还存在小径级原木出材率低、干燥板材降等问题。针对以上问题提出了翻转下锯法、自然气干+窑干+喷蒸调湿处理的联合干燥技术。 相似文献
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面对我国森林资源不足、质量不高的状况,建立和应用原木优化下锯理论,提高木材出材率已成为缓解木材供需矛盾的主要途径.本文通过提出弓形弯曲原木的数学模型,全面描述弯曲原木的解析形状,并对弯曲原木的主产出材率进行优化设计,借助计算机辅助设计实现原木优化下锯的三维再现,这对提高原木出材率和利用率、提高木材加工技术水平与现代化程度有着极为重要的实际意义和广泛的应用前景. 相似文献
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《林业科学》2016,(12)
【目的】提出将小径木纵向锯解为多块扇形木材后重组为近似板材再刨切为弦切单板的工艺,以提高原木出材率。【方法】首先对理想原木进行数学建模,并分别对短径方向、长径方向的弦切单板建立数学模型;然后以建立的原木及弦切单板数学模型为基础,绘制最优星形下锯图及最优弦切单板刨切图;最后分别对星形下锯与直接刨切2种不同工艺进行出材率计算,以比较原木出材率的高低。【结果】通过对模型的比较,短径方向弦切单板宽度大于长径方向弦切单板宽度,要求弦切单板宽度时,应以短径方向弦切单板为模型基础进行最优下刀;要求弦切单板数量时,应以长径方向弦切单板为模型基础进行最优下刀。计算出材率结果显示,相对于直接刨切,采用星形下锯工艺可以提高原木出材率。【结论】采用星形纵向锯解后重组刨切单板的工艺可提高原木出材率,同时可为实际选材提供理论支持,选择原木尺寸规格越大,出材率越高。 相似文献
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在生产小规格干燥成材的制材企业中,选择合理的原木下锯法具有重要意义。图1列举的2、3和4下锯图已在生产中广泛采用。下锯图2的锯解顺序是先将原木锯割成毛方和毛板,再将毛方锯成整边和不整边成材。当采用下锯图3和4用来锯解大径级原木时,先将原木锯割为两块或三块毛方,再将毛方锯解成整边和不整边成材。 相似文献
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目前,世界平均锯材出材率只有45%左右,有相当一部分木材削成了木片。在影响出材率的诸因素中,下锯法是一主要因素,因此,确定最合理的下锯方法,是制材工业中重要的研究课题之一。对此,欧美各国,近年来采用了光电扫描装置将检测的原木外形与电子计算机配合,实行程序控制来完成的。程控的使用,不但提高了生产效率,更重要的是显著的提高了锯材出材率。如美国,用于跑车带锯锯剖原木,可提高出材率6—15%(不用光电 相似文献
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一、前言在枕木生产中,合理下锯是节约木材、提高成材出材率和产品质量,降低成本的重要措施之一。为了做到合理下锯,需要考虑的因素很多。如弯曲原木和径差较大的5米枕资合理截锯的问题,合理留钝稜的问题,注意剔除原木的天然缺点合理配置主副产品的问题以及充分利用原木断面形状的特点提高枕木出材率的问题等。而过去在枕木生产中工人接触最频繁,潛力较大,而又尚未被人们所重视的因素就是原木断面形状与枕木出材率的关系问题。 相似文献
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Significant efforts have been made to improve teak; however, evaluation in juvenile step is limited. The objective of this study was to conduct an early assessment of the wood properties of 4-year-old Tectona grandis. Samples of 36 clones were collected to determine their morphological tree parameters [diameter a breast height (DBH), diameter of the second log, tree height, and log quality]. Presence of growth stress, heartwood percentage, shrinkage (radial, tangential, and volumetric), basic density, and ultrasound velocity (USV) were determined for standing trees, logs, green lumber, and dry lumber. The results indicate that DBH and USV in standing trees can be used to predict elastic module (ED), mainly ED of the standing tree and dry lumber, as well as the possible presence of growth stress. Additionally, growth stress can be predicted by UVS in standing tree. Tangential and volumetric shrinkage were not predicted by tree morphology, but radial shrinkage was predicted by diameter and UVS was not affected by any shrinkage. Basic density was predicted by DBH and UVS measured in log. 相似文献
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人工林小径结构用材的现状与发展趋势 总被引：1，自引：0，他引：1
目前我国人工林蓄积量居世界首位,因此木材资源结构已由天然优质大径级材向低质小径木转变,低质小径木已成为我国工业用材的主体,研究以低等级人工林小径材开发用于建筑房屋的高强度木质结构材具有重要现实意义和广阔的发展前景.本文就国内外对小径木结构材研究和发展现状进行概述,阐述人工林小径材特性,并对其发展趋势作出预测. 相似文献
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Estimation of lumber yield from a forest inventory is important in determining the optimal utilization of available regional wood supply. In this study, we review existing approaches of lumber yield estimation, including knowledge-based empirical board-foot log rules used in the United States and some regions of Canada, survey-based wood conversion factors, and optimization technology-based computer simulations. Lumber yields estimated from different approaches are then compared using six datasets from a white spruce commercial thinning experiment in Alberta, Canada. Our results indicated that (1) estimated lumber yield can be significantly different when different methods are employed; (2) board-foot log rules often underestimate lumber yield; (3) wood conversion factors represent regional average of lumber yield as a constant and thus are unsuitable for forest inventory-based lumber yield estimation; and (4) optimization technology-based computer simulations can provide the best estimate of lumber yield for a given forest inventory as long as the mill conditions and lumber dimensions from market demand are specified. Forestry investment in applying computer simulation methods should be encouraged in sawmill operations to improve lumber yield and enhance environmental protection, because, for a given amount of lumber, improving lumber yield means reduced demand for harvest operations. 相似文献
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The purposes of this study were to accumulate fundamental data on wood properties within large Sugi logs and to take applicable variations in wood properties into consideration for sorting logs and sawing patterns. The characteristics of basic density, moisture content, growth ring width, and microfibril angle (MFA) were measured and the relationship with log and lumber quality was examined. It was considered reasonable to estimate the lumber moisture content based on the moisture content of heartwood rather than that of whole logs, especially when producing large-sized lumber. The MFA reached a constant value before the 15th ring, and within a distance of 10 cm or less from the pith. Since the E fr of lumber correlated with that of the log affected by MFA, it would be possible to produce lumber with a higher E fr from the outer position of the log, based on selecting a log above the E fr . Since the MFA would also affect the lumber warp, a sawing pattern avoiding the area around the pith or enlarging the rough sawn size when a large warp was expected could be effective in improving the lumber quality. To improve the lumber quality, not only one but also multiple wood properties must be applied to the sawing pattern. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(2):182-188
Abstract Quality sorting of sawlogs based on three-dimensional (3D) or X-ray scanning or a multivariate combination of variables from both methods may be used to decrease the production of off-grade products carrying unwanted combinations of dimension and grade. There is, however, potential for further improving the sorting accuracy if 3D and X-ray raw data are combined at an early stage using path length compensation. From the measured 3D shape, a good estimate of the length of each X-ray path through the log can be made, enabling the calculation of a log density profile from the measured X-ray attenuation. The effect of this technique on heartwood diameter measurements of 423 Scots pine (Pinus sylvestris L.) logs was evaluated. By the addition of 3D data to the X-ray data it was possible to raise the predictability of the heartwood diameter from R 2=0.84 to 0.95 and to improve the root mean square error from 17 mm to 9.3 mm, primarily because of the enhanced contrast between heartwood and sapwood. 相似文献
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Impact of precommercial thinning on tree growth,lumber recovery and lumber quality in Abies balsamea
《Scandinavian Journal of Forest Research》2012,27(5):425-433
Abstract Precommercial thinning (PCT) is often used to improve stand growth and value. While PCT may accelerate tree growth and reduce mortality, it may also have a negative effect on product quality. This study examined the effect of moderate and heavy thinning on tree growth, lumber recovery and quality in a natural balsam fir [Abies balsamea (L.) Mill.] PCT trial 35 years after thinning. Compared with the control, the heavy thinning increased merchantable tree diameter, stem volume per tree and lumber volume recovery per tree by 41.1%, 100.9% and 92.7%, respectively, reduced the Select Structural grade (the best grade) recovery by 33.7%. Thinning did not affect the no. 2 and better grade yield. There was a 12.2% and 15.0% difference, respectively, in the lumber bending modulus of elasticity (MOE) and modulus of rupture (MOR) between the control and heavy thinning. Moderate thinning had little impact on the visual grade recovery, lumber bending MOE and MOR. Heavy thinning is recommended if the goal is to get sizeable sawlogs in the shortest time, whereas moderate thinning is preferable if the intention is to minimize the negative effects on lumber quality while retaining modest tree growth and lumber recovery. Overall, PCT of very dense young balsam fir stands appears to be an effective and viable silvicultural treatment. 相似文献
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