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VOLUME 50, ISSUE 1/2009

Machining of tree discs to evaluate the annual growth rings with turn-milling Part 1

Language: German
Pages: 5 - 10
Authors: Johannes Tröger, Sergey Martynenko, Kai Schumacher, Frank Rinn

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The analysis of the pattern of annual growth rings is done by a lot of different disciplines: Phytology, wood biology, climatology, pollution control, geography, ecology, archaeology, architecture, science of forestry etc. But the machining of

cross-grained wood is one of the most difficult grinding tasks in woodworking. Up to now, such tree discs are prepared with a special machine, which cuts the surface with a sharp blade. This solution is very expensive, because for every test specimen a new blade is required. Furthermore it is just possible to prepare a small stripe instead of the whole disc. With the machining process of turn-milling it is possible to finish such tree discs in an adequate quality and in a short cutting time. In part 1 the milling strategy and the test equipment are shown. Part 2 will follow with the experiment parameters and the results.

Influence of moisture content on Brinell hardness for different wood-based materials

Language: German
Pages: 11 - 16
Authors: Walter Sonderegger, Peter Niemz

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Brinell hardness was determined under different climatic conditions (relative humidity (RH) 35 % to 95 %) on industrially produced wood-based materials. Furthermore, different evaluation methods depending on the penetration depth were used. Clear differences were revealed between the different wood- based materials. The hardness tends to increase with increasing density whereas clear differences exist between the tested materials. With increasing equilibrium moisture content (EMC), the hardness clearly decreases.

Thermo-smoothing of wood based material by using of parallel kinematics

Language: German
Pages: 17 - 22
Authors: Christoph Raatz, Steffen Rehn, Axel Petrak, Knut Großmann, André Wagenführ

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Aim of the project was to divide the milling and smoothing process of MDF-profiles in two machine steps. Milling is traditionally performed on a CNC-router. The presented solution provides smoothing of the workpieces edge and front profiles on a separate equipment. This parallel kinematics combines referencing of workpiece and adjustment of the heated smoothing tool. A force control was developed which controls the path of the smoothing unit by measuring the smoothing forces. The parallel kinematics equipped with smoothing unit and force control were shown to successfully operate as separate processing unit for distribute the smoothing step onto a separate machine successfully.

Manufacturing of organically bonded beech insulating boards

Language: German
Pages: 23 - 26
Authors: Michael Bartholme, Georg Avramidis, Wolfgang Viöl, Alireza Kharazipour

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Insulating boards of beech fibres were produced in a wet process in laboratory scale. Boards without any binders had low stability whereas boards with potato pulp reached higher stability. The tensile strength perpendicular to faces and the compressive strength could be improved by adding 10 % potato pulp to the fibre suspension. Heat conductivity of beech boards was higher than of equivalent boards made of softwood but heat conductivity was not negatively affected by the potat pulp. It was also shown that microwave drying of wet processed fibre mats can significantly shorten the drying process compared to convective drying in a drying cabinet. The appearance of "Hotspots” during micro waving the boards was a problem. This was solved by moving the boards in the oven on a conveyor belt and by reducing the microwave power at the end of the drying process.

The coherence between annual ring texture and acoustic characteristics of resonance wood Part 1: Determination of the sequence of the annual ring widths at the standing trunk

Language: German
Pages: 27 - 31
Authors: Gunter Ziegenhals

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The goal of the work described in this article was it to already win as much as possible information over the resonance wood quality, which can be expected at the standing trunk. The classical resonance wood characteristics and their ranges of values are compiled. Then we describe investigations with the drilling needle equipment " Resistograph 1410". In the result of the investigations one can state that the drilling needle method of analysis with sufficient accuracy supplies the sequence of the annual ring widths in the trunk.

MDF powder coating – the development of a new environmental friendly technique

Language: German
Pages: 32 - 37
Authors: Marius Catalin Barbu, Thomas Schmidt

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Since years specialists try to adopt the advantages of metal powder coatings to the wood and MDF panel processing. An exceptional challenge on that way in the past was the interdisciplinary cooperation between equipment suppliers, MDF manufacturers and powder producers. The advantages of powder coatings – environmental friendliness, freedom of design, robust surfaces – allow a successful competition to established

finishing technologies such as liquid coatings or PVC foil. The development of MDF boards suitable for powder coatings showing optimised mechanical-physical properties was a crucial factor in this development. Modern requirements such as low emission boards should be considered essential to further improve the image of powder coating as an exceptional environmentally friendly and sustainable technology.

Methods to determine mass fractions of lignocellulose- thermoplastic composites

Language: German
Pages: 38 - 42
Authors: Alexander Reichert, Hans Korte

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The new material class of wood or natural fibre-plastic composites (WPC, NFPC) show a dynamic market increase. There are some Austrian norms, European technical specifications and a German Quality seal but no analytics to determine

and to quantify the ingredients. This publication uses soxhlet extraction with xylene to separate the lignocellulosic fraction from the plastic fraction (polyolefine) including additives. Differential scanning calorimetry (DSC) is used to differentiate between polyethylene and polypropylene in the plastic fraction. DSC is also used to verify the completeness of extraction. Sugars from sulphuric acid hydrolysis of the lignocellulosic

fraction are converted to alditol acetates or aldonitrile acetates for gas chromatographic characterisation. In combination with ash content sugar analysis allows distinguishing between soft and hard woods and in one case rice husks as lignocellulosic source. The analytics are demonstrated at nine industrial samples.

Development of a test method to determine the resistance of insulation materials against mould

Language: German
Pages: 44 - 49
Authors: Wolfram Scheiding, Kordula Jacobs, Katharina Plaschkies, Björn Weiß

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The theme "Development of a test method to determine the resistance of insulation materials against mould" was one of five independent R&D projects within the joint project "Investigations on optimisation and standardisation of insulations from renewable raw materials". Within the project, a modified test method was developed, which includes several improvements, comparing to the hitherto existing standard test

methods. Tests were carried out with different materials according to the standard an the modified test method. The modified method was verified by tests at the Federal Institute for Materials Research and Testing (BAM). It is documented as a process instruction of IHD and was referred to the appropriate CEN/TC 88 "Thermal insulations" for discussion and possible establishment as an European test standard.

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