JAHRGANG 46, AUSGABE 4/2005

Deutscher Text

The objective of this study was to describe the usual cutting techniques of beech logs for the production of high-quality sawn timber and to simulate the influence of red heartwood and log dimension on the yield of produced sawn timber using different sawing patterns. First of all a concept for a calculation model simulating three sawing patterns was developed. Important cutting methods for beech logs are live log sawing, tangential cutting and double cut. Tangential cutting is most often chosen in sawmill practice for a quality-oriented cut. The calculation results showed that live log sawing is less suitable for the production of high-quality sawn timber from beech logs with a large proportion of red heartwood. Using the tangential cutting-technique, the band saw can be flexibly adjusted to the beech log dimension and to the open laid internal defects like heartwood. An additional calculation of the revenue and the marginal income describes the economic correlation between the amount of red heart at the top log diameter and the yield of produced sawn timber for each investigated cutting pattern.

Panel-shaped composite materials with a paper honeycomb core have been used for years to manufacture lightweight furniture components. Panels with paper honeycomb core are currently produced discontinuously. Lightweight panels for furniture and interior design applications are mainly produced in frame construction (with wooden frames for edge closure and for fixing fittings). At the Catholic University of Leuven (Belgium), the paper folding honeycomb "TorHex", which can be produced continuously from corrugated board laminated on both sides, was developed. The folding honeycomb is intended as the core layer of continuously produced, lightweight and frameless sandwich composite panels. Under laboratory conditions, novel, thin lightweight panels with a folding honeycomb core were produced. The panels were tested in mechanical tests for their flexural strength and transverse tensile strength, among other things. A comparison of these properties with chipboard as a conventional furniture material allows conclusions to be drawn about specific applications.

Pulps from pine chips were prepared using the chemothermo-mechanical process (CTMP-process). Part of the obtained pulps was washed by water at room temperature to remove water soluble components. The pH-values and the buffering capacities of cold water extracts and the release of volatile acids (formic and acetic acid) of the unwashed and washed pulps were measured. Moreover, MDF were prepared with alkaline curing PF-resin from unwashed and washed fibres under exactly the same condi- tions and their properties were assessed. The results reveal: Washing of pulps increased the pH-value of the pulp water extracts and decreased both the buffering capacity towards alkali and the emission of volatile acids (formic and acetic acid) from the pulps. Moreover, the internal bond strength and the internal bond strength after boiling (V100-value) of PF-bonded MDF were increased significantly. Washing of pulps reduced significantly the thickness swelling (24 h) of the boards and reduced the emission of volatile acids significantly, however it increased the formaldehyde release.

The principal purpose of an investigation which was carried out at the Institut für Holztechnologie Dresden gGmbH (IHD) consisted in deepening the knowledge to the moisture household within woodworks and its temporal development under the influence of external moisture. New sensory concepts for the monitoring of moisture transport processes were developed and utilised. The measurement of the equilibrium air moisture in cavities within the wood and the capacitive moisture measurement directly in the boundary layer wood-coating turned out to be innovative and practicable approaches. In outdoor weathering tests appeared that a long-term recording of the relative air moisture and the mass of coated test pieces offers a possibility to observe the ageing behavior of the coating practically oriented and quantifiable. One was found out that the correlation of the relative air moisture and the test piece mass can be changed in long intervals and that from this change conclusions on damages in the coating can be drawn.

After mainly Finnish, Dutch, and French Producers established thermally treated wood on the timber market in the late 90s, several firms from different European countries are offering a wide range of thermal modified timber at the time. The material got especially in place for floorings, garden furniture and decking. The offered products have normally the same properties that have been discussed in several papers. At the ETH the work group wood physics has, with financial support of the Swiss "Fonds zur Förderung der Wald- und Holzforschung", realised a project concerning the distributors and consumers experiences with thermally treated wood. Favourable statements prevail, nevertheless there have also been problems with the material, which have yet been partly eliminated. In the future the major task of the producers will be to reduce problems and produce reliable quality.

The Institute for Research and Development of Musical Instruments, adjacent institute of Dresden University of Technology, and the chair for Wood and Fibrous Materials Technology of Dresden University of Technology worked on a research project for the application of thermally modified wood in musical instruments. The goal of this project was to analyse the changed physical, anatomical and chemical characteristics of modified woods and to compare them to characteristics being relevant for musical instruments. Conclusions on the possible use of these woods in musical instruments were drawn. In part 1 of this publication selected anatomical and physical characteristics are described, Part 2 (estimated appearance in issue 1/2006) is concerned with technological characteristics and the production and examination of parts of musical instruments.

In cutting wood and wood based materials (e.g. by sawing), the highest possible throughput has been reached. In the meantime, cutting by-products decrease yield considerably. Sawdust is most prominent of these by-products. 40 to 50 % of the sawdust particles do not reach 1 mm in size. These small, respirable dust particles descend into the lungs and stay there, causing damage. Cutting tools that do not produce sawdust may eliminate this problem. Such method is cutting wood using a water jet. This appears to be an economical and environment friendly technique. The authoress describes the results of her experiments, in which she examined the moisture uptake by the material, kerf width and the quality of the cut surface.

On 4 wood species from southern Chile namely Nothofagus pumilio, Nothofagus dombeyi, Nothofagus alpina and Podocarpus nubigenus the density, the sound velocity and the dynamic MOE in the three main directions was ascertained. The measured sound velocities were used to calculate the dynamic modulus of elasticity. The sound velocity measured was conspicuously in the radial direction higher than in the tangential direction.

In the timber trade, the timber industry and the construction industry, discussions about the designation of wood species are a recurring theme. It is not uncommon for such differences between the names offered and standard names to lead to irritation. DIN EN 13556 "Nomenclature of commercial timber used in Europe" specifies standard names in three languages for round and sawn timber (D = German standard name; GB = English standard name; F = French standard name).