VOLUME 59, ISSUE 3/2018

Milling is one of the most important cutting procedures in the wood industry. It allows planing, profiling and shaping of workpiece surfaces with a high chip-removal rate. This is possible because of a fast rotary cutting motion of the tool, the possibility to place many cutting edges on the tool circumference and a fast linear feeding motion of the workpiece or the tool. Due to these different kinds of motions (rotary and linear) the resulting effective motion during the cutting process follows a prolonged cycloid. Periodic waves are formed on the workpiece surface due to this cycloid motion. These surface patterns, called cutter-marks, may be visible on the machined surface after cutting and mainly influence the workpiece quality. Further surface machining steps are required, like sanding or slicing to meet the required standards of surface quality and roughness. Therefore, extra efforts and costs are incurred, as well as additional production steps and time, in order to finish shaping the workpiece. This is why researchers have been looking for possibilities to lower or avoid these cutter-marks for some time. Beside the description and the analyses of the geometry of cutter-marks, magnitudes of disturbance, mechanical and mechatronic approaches and alternative procedures will be introduced, discussed, compared and presented in the paper. Especially mechatronic approaches using modern hardware can improve this situation by basically adjusting the cycloid motion track when the cutting edge approaches the work piece. In this way, the effective motion of the cutting edge is changed to a nearly linear motion by means of piezo-electric actuators or magnetic bearings. First successful set-up and experiments will be shown.

Thin kerf sawing is a precision cutting technology to produce high quality lamella mainly for parquet industry. This work compares the cutting forces obtained by machining six wood species in two main cutting directions (A and C). Results from cutting in A-direction show well known behaviour with linear increasing cutting forces with cutting depth and tool width. In contrast cutting in C-direction shows nonlinear behaviour, which is better described with a polynomial function. Different micro-deformations and in-depth-damage in the grain direction observed at the secondary cutting edges might be the reason for this observation.

Oil Palm Wood (OPW) a by-product of the palm oil industry has become an increasingly important raw material due to availability in enormous quantity and due to the lack of traditional wood species in many parts of the world. Extensive studies and projects have found uses of OPW for products with high economic potential. Despite many promising facts and results the nonuse of OPW on an industrial scale is mainly due to the complexity involved in drying and machining processes. Due to the materials unique structure suitable drying parameters and techniques are required to avoid cell collapse. Machining difficulties arise from the consequences of the upstream processes (preservation, drying) and mainly due to the highly varying density distribution and extremely abrasive nature due to the presence of silica particles. This study aims on detailed observation and analysis of machining techniques of OPW. And as a result to create product oriented machining solutions with optimized cutting tools and machining processes. A series of machining operations was performed to evaluate possibilities of planing, routing, sawing, drilling and boring. Findings of this study showed that cutting material, cutting edge geometry and cutting dynamics play a vital role in tool wear mechanism while machining OPW. Significant effects of defective drying process by means of pre-splitting and tear outs were observed for different machining processes. Further, the role of cutting kinematics in relation to the morphology of the material was identified. The influence of the moisture content to the abrasiveness of the material was also found. Results of this study have provided further scientific understanding of the material itself and its behaviour while processing. This would help to overcome the difficulties in machining OPW, in developing and optimizing machining processes, also in determining optimal cutting material and cutting geometry.

Formaldehyde-free resins can be prepared by substituting formaldehyde by alternative aldehydes as described herein, glyoxal and gloxylic acid. The synthesis of the resin is easy to implement and requires no new technology. Both the processability and the durability of the formaldehyde-free resins meet the requirements of industry. With this formaldehyde-free resin various wood materials with good mechanical properties and very low formaldehyde emissions were produced. The hygroscopic properties have to be adapted by means of a suitable hydrophobing agent. The pressing times could be shortened by optimizing the formulation. The particleboards as well as the fibreboards reach the requirements described in the standard. Thus, the preparation and processing of the formaldehyde-free amino resins corresponds to that of formaldehyde-containing amino resins, but a further reduction of the press time is necessary.

The results of this paper are part of a research project launched in October 2015 by the Papiertechnische Stiftung Heidenau/Sa. and the Institute for BFSV at the University of Applied Sciences Hamburg. The aim of the project was the development of a method based on continuum mechanics for the calculation of the climate-dependent creep behaviour of corrugated board packaging. Using velocity-controlled short-term tests on corrugated cardboard samples, the generalized Maxwell model and the Prony analysis, it is possible to calculate the creep behaviour of corrugated cardboard samples under standard climate. By comparing the measured and calculated creep rates this assumption could be confirmed. In further series of tests, the creep behaviour in wet and alternating climate was the focus of the investigations. At the end of the research project, it should have been possible to use the results and the finite element method to present a simulation of the behaviour of corrugated packaging over a certain period of time up to failure.

Terrace or balcony decking is an important application for solid timber or wood-based material. Although the demand for wooden decking or cladding is performing positive, problems and complaints with the appearance arise increasingly. The changes in appearance are concerning both uncoated and coated commodities, and often occur already after a few weeks or months. Reasons are often discolourations, which are caused by micro-organisms or result from weathering or chemical reactions. This article is dealing with characteristics and problems of assessing of visual appearance (aesthetic function) and of visual deficiencies, respectively.