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VOLUME 48, ISSUE 4/2007

The PrimWood method Part 1: Properties and production of timber with vertical annual rings

Language: German
Pages: 5 - 9
Authors: Dick Sandberg, Jimmy Johansson

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Old traditions and modern measurements show that radial sawn wood is subject to smaller moisture movements in the plane of the surface and has a harder surface and better shape-stability than timber sawn by conventional sawing techniques such as square sawing and through-and-through sawing. The advantages are greater if the juvenile wood is removed. Timber with radial faces and where the juvenile

wood has been removed is said to have vertical annual rings, and such timber is particularly valuable for products such as floors, furniture, panels and exterior carpentry. The special properties of the timber are then utilised in the best possible manner. The PrimWood method is a new production concept for

the manufacture of high quality wood components and boards of massive wood from both softwood and hardwood. The concept leads to a knot-free material with vertical annual rings.

Biological modification of the lignocellulose fibres for cement-bonded fibreboards

Language: German
Pages: 10 - 16
Authors: Nguyen Trung Cong, Holger Unbehaun, Swetlana König

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Lignocellulose fibres contain inhibitors, which disturb the hydration process of the cement. In order to use these fibres as raw material for cement-bonded fibreboards, their negative effect to cement hydration must be reduced or eliminated. Therefore, the fibres from different woods and plants were biologically modified with micro-organisms (mould and lactic acid bacteria) and enzymes (xylanase, cellulase). The influences of the modification on the reduced sugar content of the fibres, the cement hydration process and the properties of the cement-bonded fibreboards are quantified and discussed. The biological modification of lignocellulose fibres could lead into improvement of the properties of the

cement-bonded boards made from these fibres.

Substitution of PMDI for the production of OSB

Language: German
Pages: 17 - 20
Authors: Holger Dube, Björn Lilie

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Since the costs for adhesives form a substantial part of the overall costs of wood-based products, especially of OSB, studies have been conducted to use more cost-effective adhesives in the form of adhesive combinations to produce such panels. The focus was on the influence of such adhesives on

the thickness-swelling properties of said panels. Lab trials have shown that it is possible to partially substitute PMDI resin with MUPF resin of particleboards made from long strands. The more MUPF resin is substituted with PMDI, the more the mechanical properties go down, however, not below the minimum requirements of EN 300 for OSB/3 and OSB/4, respectively. On the other hand the values for thickness swelling are positively influenced.

Reinforcement of small wooden sections with fibre reinforced plastics Part 2: Different fibres and adhesives

Language: German
Pages: 21 - 26
Authors: Mario Zauer, André Wagenführ, Christian Gottlöber

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At the Institute of Wood and Paper Technology of TU - Dresden in cooperation with the company Berlebach investigations for the development of a fibre-reinforced astronomy stand were accomplished. Fundamental investigations to the behaviour of load capacity, deformation and vibration behaviour of fibre-reinforced wood composites with small cross-sections have been done. In the part 1 of this publication (holztechnologie issue 3/2007) the behaviour of load capacity and the deformation of composites of wood and carbon fibre reinforced plastics are demonstrated. The following part 2 is dedicated the reinforcement of wood with different synthetic fibres respectively adhesives.

Flexible Automation for the cost-effective machining of shaped wooden parts with hexapods Part 4: Variable manufacturing environment for compact small-sized parts

Language: German
Pages: 27 - 32
Authors: Knut Grossmann

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This paper-series show potentials of efficient automation in the manufacturing shaped wooden parts based on the hexapod of simple design. In the first part [1], the spectrum of parts and the hexapod were characterized. The second part [2] introduces the “Parallel kinematic machining centre for shaped wooden parts” for the machining of a seat shell. In the third paper [3], the all around machining of parts which part-dimensions were significantly larger than the workspace of the machine has shown. In the closing part the application project “Variable manufacturing environment for compact small-sized parts” will be introduced. This project has been executed together with the professorship of Woodand Fibrous Materials Technology (Prof. Wagenfbhr). The example concerns drilling and milling of wooden balls. Here

is an extra challenge of automation in addition to referencing and technological programming which are described in [2] and [3]. The new challenge was to integrate the clamping concept in the automatic cycle of the all around machining.

Investigation of clamping on a CNC router Part 1: Basics and methodology

Language: German
Pages: 33 - 37
Authors: Etele Csanády, Szabolcs Németh

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Computer controlled machining equipment and centres that provide accuracy in the thousandth millimetres range, represent the pinnacle of woodworking technology. When cutting happens and, as a consequence, forces act in several different directions. For micrometer precision control of the cutting tool, work pieces have to be fastened securely, deprived from their degrees of freedom, to achieve maximum quality. The most frequent clamping method for pieces with planar surfaces today is fastening by a vacuum field. The vacuum-induced hold-down force, together with l0 and l (static and kinetic friction coefficients, respectively) creates the friction force that prevents the work piece from shifting.

The purpose of numerous measurements was the Analysis of the work piece movement. The shifting of the material upon intensive cutting or at the start of the cutting process is a frequent problem. In this article with two parts the friction coefficients when clamping work pieces of different wood species resp. wood materials by vacuum under different conditions are to be investigated.

Testing System – Mechanical Resistance of Windows and Doors

Language: German
Pages: 38 - 42
Authors: Joachim Beständig

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Mechanical performance capability is a substantial quality feature of windows and doors. In this testing area, European test standards regulate the technical requirements, parameters and methodical approaches in detail. Technical concepts regarding devices that would facilitate standardised technical implementation and comparability of tests are, as a rule, not available. A technical basis for a modular testing system to prove mechanical performance features of windows and doors based on the product standard DIN EN 14 351-1 that is relevant to these components has been developed and a functional

sample has been set up. This testing system has especially been designed for permanent functional testing and for determining operational forces as well as mechanical strength. The resulting testing system is user friendly and Permits reproducible testing. Owing to its modular design and the flexibility of the testing system, users can implement custom-made solutions.

Analysis of failure behaviour of glued joints at tensile shear loading

Language: German
Pages: 43 - 47
Authors: Peter Niemz, Melanie Wyss, Matthias Fuhr

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Adhesive joints with 1K-PUR, PVA and urea resin had been tested according to DIN EN 205 for shear strength, ultimate strain and tensile energy absorption for different adhesives and joint thicknesses. For the determination of the strain of the glued joints additionally to the optical extensometer the measuring system VIC 2D was used. Therefore the loading procedure has been filmed by using a high-resolution

video camera; the pictures had been analysed by cross correlation using the VIC 2D measuring system. The ultimate strain was smallest when used urea resin. Using 1K-PUR ultimate strain increases and shear strength decreases with growing joint thickness. Extension perpendicular to the glued joint was highest in the middle of the joint, parallel to the glued joint it was highest at the ends of the joint.

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