基于数控C功能刀补的木材复式压缩弯曲方法

应用数控C功能刀补方法,解决了木材复式弯曲中无固定回转中心或曲率变化较大的弯曲构件的复式压缩弯曲成形问题;确立了C功能刀补应用中端面压缩机构的圆弧进给量的计算方法.     

金属薄板旋弯成形装置

针对新产品研制过程中金属薄板弯曲成形这一加工难点,分析了薄板零件主要形状与结构特征,比较了常见成形工艺的优缺点和加工适用的范围,提出旋弯成形这一新的工艺方法及相应工艺装备设计,重点介绍金属薄板旋弯成形装置的结构设计,使用方法及应用效果。     

竹制家具弯曲构件加工方式

本文从竹制材料进行划分,系统阐述了竹制家具弯曲构件的加工方式。圆竹弯曲构件常采用火制工艺和开槽的方式进行弯曲。竹片基材弯曲构件需要进行软化、弯曲、干燥、胶合等多道工序进行加工处理。竹集成材则以锯制为主要的加工方式制作弯曲构件。竹制家具弯曲构件加工方式的研究为丰富竹家具制品造型提供了技术支持。     

多工位梁柱型家具构件成形机床的工艺分析与总体布局

文章针对传统梁柱型家具构件成形加工设备的加工工艺,确定多工位梁柱型家具构件成形机床的工艺流程和加工对象。通过研究现有的梁柱型家具构件成形加工设备的主要技术参数,明确了多工位梁柱型家具构件成形机床的主要技术参数。根据对多工位梁柱型家具构件成形机床的设计原则,制定了合理的总体布局方案。     

拉伸牦牛绒复式纱加工技术

主要介绍了自主开发的TJGD-QHXZSR-09型绒毛拉伸机,包括自动喂入、预处理、拉伸、定形和烘干部分,能够对长度较短的牦牛绒等纤维条实施连续加工。介绍了一种复式加工纺纱系统的改造措施,主要技术要点包括:并条机的复式条成形改造;粗纱机及细纱机复式纱成形的加工技术;分析了有捻粗纱机和无捻粗纱机对细纱机喂入的影响。并将拉伸牦牛绒纤维在改造的半精梳绒毛复式加工系统上开发了10.4 tex×2×2复合股纱线。经过织片试验表明,产品抗起毛起球性能明显提高。     

刚柔相济的魅力

家具经历了漫长的历史,制作家具使用最多的是木材。 木材有着种种的优点,但也存在着一定的局限性。如木材的弯曲性能较差,弯曲变形稍大就会劈裂。所以我们常见的木质家具部件,大多是直的,即使必须使用弯曲部件时,也只好是在大块的木材中锯割出来。象中国传统家具的圈椅上的扶手与靠背相连的大圈,就是用五块弯料相接做成的,而法国路易式家具中的弯腿,也同样是使用大块木材,四面锯割成形的。这种加工工艺,     

构建安全、健康、舒适的居住环境——建筑与室内外装饰用日本木材产品介绍

<正>日本的森林覆盖率高达66%,是世界上屈指可数的森林之国。今天,日本在吸收了源自中国的众多文化和文明的基础上,创新发展为具有高度木文化的国度。在长期的木材利用过程中,日本创造了先进的木材利用技术。特别是在近十年中开发了住宅构件的预制加工、金属连接件、构件一体化等众多的先进技术和高性能的结构用胶合板、胶合木、LVL等制品。丰富的日本杉、日本柏、日本落叶松等优良木材和低成本的海运使资源和市场的对接成为可能。我们相信日本的木材一定能够获     

米歇尔索耐特的木材弯曲技术研究与应用

通过研究米歇尔·索耐特的木材弯曲技术,灵活而创新性地应用到现代家具设计与制作中来。通过对米歇尔·索耐特的三项木材弯曲技术,即层积单板弯曲技术、层压盘条弯曲技术和实木弯曲技术,分别从技术手段、工具设备、工艺设计等方面进行详细的分析和研究;总结出米歇尔·索耐特木材弯曲技术和工艺优缺点,得出其相应的应用领域和应用方式,并具体解析其最经典的实木弯曲工艺;在综合利用索耐特木材弯曲技术原理基础上,经过部分技术创新和工艺调整,设计并成功制作了"芽"弯曲椅,对索耐特弯曲技术进行印证和发展。     

构建安全、健康、舒适的居住环境——建筑与室内外装饰用日本木材产品介绍

日本的森林覆盖率高达66%,是世界有名的的森林之国。今天,日本在吸收了源自中国的众多文化和文明的基础上,创新发展为具有高度木文化的国度。在长期的木材利用过程中,日本创造了先进的木材利用技术。特别是在近十年中开发了住宅构件的预制加工、金属连接件、构件一体化等众多的先进技术和高性能的胶合板、胶合木、LVL等制品。丰富的日本杉、日本柏、日本落叶松等优良木材和低成本的海运使资源和市场的对接     

锌合金在木材工业中的应用

木材工业的发展使木料综合利用率不断提高,近年来木制品的基材、结构和生产工艺都发生了根本的变化,传统的天然木材框架式结构被以人造板为主的板式结构所代替,长期沿用的以切削加工为主的木材加工工艺在现代木制品加工工艺中所占的比重大为下降,代之以实木弯曲、单板弯曲胶合、碎料模压成型及模压浮雕等木材综合利用率较高、对材质要求较低的少无切削加工工艺。不但可以利用废材、枝桠、小径级材,而且大大缩短制品的工艺流程,减少设备投     

实木顺纹压缩弯曲技术研究现状及发展趋势

实木顺纹压缩弯曲技术蕴含着多学科知识的交叉融合,具有一定的理论深度和突出的实际应用性,是当今备受关注的研究热点之一文章论述了国内实木顺纹压缩弯曲技术的研究现状与发展趋势,描述了国内研究学者在树种选择、木材软化与顺纹压缩、木材弯曲等方面的研究成果,提出高效利用木材资源、提升自动化程度、提高木材弯曲精度的发展趋势,为今后国内实木顺纹压缩弯曲技术的研究提供借鉴。     

Holzqualität von Kiefern aus einem Waldschadensgebiet nach fünfjähriger Naßlagerung

The wood of heavily damaged pines (damage class 3) and that of pines free of any damage (damage class 0) was compared with green wood after 5 years of storage under sprinkling water. Altogether 30 sample trees from the Sellhorn forest district in Lower Saxonia were examined regarding the following wood properties: wood density, static compressive and bending strength, modulus of elasticity in bending as well as impact bending strength. The obtained results show that neither damage class nor many years of wet-storage had a negative effect on wood density respectively on elastomechanical properties. A devaluation of the Scots pine logs by wood descoloured blue staining could be successfully avoided after wet-storage.     

Zerstörungsfreie Bestimmung elastischer Eigenschaften quadratischer 3-schichtiger Brettsperrholzplatten mit symmetrischem Aufbau

Some of the most important material properties of engineered wood products, like cross-laminated solid wood panels, are the elastic properties. Regarding panels, the two in plane MOEs (E_ii) and three shear moduli (G_ij) are of particular interest. In order to determine these parameters with an economically and non-destructive technique, a method was developed which allows to determine all five parameters in one experiment only. This method was approved on 24 square-shaped cross-laminated solid wood panels with side-length of 2.5 m, thickness of 70 mm and two different layer sizes. The panels were produced by two plants applying different technologies. The determined elastic parameters were verified by bending tests and compared with stiffness parameters calculated on basis of the elastic compound theory. Four elastic parameters could be determined and proven to be correct. The results did neither depend on the different production technologies of the panels nor on the two different compositions of layers. The determinability of the elastic parameter G₂₃ depends on the geometry of the panels. Noteworthy is the fact that stiffness parameters calculated assuming that the raw material of the single layers corresponds to strength class C24, can be on the ‘‘unsafe side’’.     

Biegefestigkeit von Fichten- und Kiefernholz aus Waldschadensgebieten in Bayern

The influence of new forest damage on the bending strength of small defect-free wood specimens from spruce and pine, was investigated in the wood from six Bavarian forest areas. All damage classes from 0 (=sound) to 4 (=dead) were represented. The well known relationship between strength and density became evident and showed no influence of the damage class. Also, the comparison with strength data, determined before damage occured in the forests, gave no indication of a strength reduction in the wood of damaged trees.     

Prediction of timber bending strength and in-member cross-sectional stiffness variation on the basis of local wood fibre orientation

Machine strength grading of structural timber is based upon relationships between so called indicating properties (IPs) and bending strength. However, such relationships applied on the market today are rather poor. In this paper, new IPs and a new grading method resulting in more precise strength predictions are presented. The local fibre orientation on face and edge surfaces of wooden boards was identified using high resolution laser scanning. In combination with knowledge regarding basic wood material properties for each investigated board, the grain angle information enabled a calculation of the variation of the local MOE in the longitudinal direction of the boards. By integration over cross-sections along the board, an edgewise bending stiffness profile and a longitudinal stiffness profile, respectively, were calculated. A new IP was defined as the lowest bending stiffness determined along the board. For a sample of 105 boards of Norway spruce of dimension 45 × 145 × 3,600 mm³, a coefficient of determination as high as 0.68–0.71 was achieved between this new IP and bending strength. For the same sample, the coefficient of determination between global MOE, based on the first longitudinal resonance frequency and the board density, and strength was only 0.59. Furthermore, it is shown that improved accuracy when determining the stiffness profiles of boards will lead to even better predictions of bending strength. The results thus motivate both an industrial implementation of the suggested method and further research aiming at more accurately determined board stiffness profiles.     

Neue Untersuchungen mit Nägeln für den Holzbau

With partly new test methods the yield moment as well as the withdrawal resistance of the nails was determined taking into account the influence of the wood density, the fabrication quality, the shank shape and the smoothness of the nail surface. Tests show, that the yield moment can only be determined using a nail bending test. The bending resistance of common wire nails was specified depending on the nail diameter. Withdrawal tests using annularly threaded nails showed a good correlation between the withdrawal resistance and the squared density of the wood. Because of the strong influence of the fabrication tolerance on the withdrawal resistance, the compliance of small fabrication tolerances is necessary to guarantee the required quality. The influence of the roughness of the nail surface was particularly obvious for common nails.     

Melaminharzbasierende duromere WPC – Steuerung der Verarbeitung und der Eigenschaften

This article exemplarily describes the influence of wood, two thermoplastic additives and process conditions on the processability and subsequently on the obtained bending properties of melamine-resin based wood polymer compounds. Before a wood-melamine resin-compound can be processed its reactivity has to be understood. This allows for estimating if and how the process can be realised. Besides previous chemical plasticization of the melamine resin, some additives need to be employed. These in turn influence the reactivity of the compound as well as the mechanical properties of the resulting composites. The main parameters controlling these effects are compatibility and acidity. Even the wood type affects the cross-linking reaction of the melamine resin with regard to temperature and time. Depending on adaptations to the process and the respective formulations processing as well as the properties of the final product can vary substantially. Only if all these effects regarding formulation and extrusion parameters are taken into account, melamine-resin based wood polymer composites of high quality can be produced.     

Untersuchungen zum Einfluss der Holzfeuchte auf ausgewählte Eigenschaften von Spanplatten und MDF

On industrially produced particle boards and MDF, the influence of wood moisture on bending MOE, bending strength and shear modulus G_zx and G_zy was determined. The equilibrium moisture content and the differential swelling of thickness proved to be smaller for MDF than for particle boards. Tensile strength and tensile MOE, shear modulus and bending strength decrease likewise with increasing wood moisture content. Furthermore the Poisson ratio μ₁₂ decreases with increasing wood moisture content.     

Temperature and moisture content behaviour in microwave heated wood prior to bending – Mountain Ash (Eucalyptus regnans)

The Cooperative Research Centre for Wood Innovations, within the University of Melbourne, has developed an innovative wood bending technology which involves the use of microwave softening of wood prior to bending, an automated process of wood bending suitable for ‘‘mass production’’ and microwave drying of bent components. This paper discusses the microwave softening of wood required prior to bending, in particular, temperature and moisture distribution and transmission in cross-sections of microwave heated wood. Optimal heating parameters for softening wood using microwave irradiation were also investigated.     

Elektronenmikroskopische Darstellung von strukturellen Einzelheiten in Nadelholz-Zellwänden anhand sehr dünner Ultramikrotomschnitte

An improvement of the embedding and staining method for the study of wood tissue in the transmission electron microscope enables a detailed representation of the lignin distribution in the various cell wall layers. Studies of very thin sections of spruce tracheids show that the strongly lignified “compound middle lamella” includes also the outer part of the secondary wall 1. In the secondary wall 2 of untreated wood a concentric lamellation was made visible. An irregularly lamellar lignin distribution in the S1 and the S2 of compression wood tracheids could also be found by the new method.