WOOD RESEARCH Volume 61, Number 3, 2016
JOZEF KRILEK, Ján Kováč, Štefan Barcík, Ján Svoreň, Milan Štefánek, and Tomáš Kuvik

The influence of chosen factors of a circular saw blade on the noise level in the process of cross cutting wood

Research was focused on evaluation of a circular saw blade tooth spacing on maximum equivalent noise level LAeq in the process of cross cutting wood. There were used circular saw blades with uniform tooth spacing and a full body and non-uniform tooth spacing with dilatation gaps. The measurements were done on the measuring device which was designed at the Department of Environmental and Forest Technology where it has been modernised. For research, testing samples of three wood species i.e. spruce (Picea abies), pine (Pinus sylvestris) and beech (Fagus sylvatica) were used. In the cutting process, two feeding speeds were set up with the same revolutions of circular saw blades and for more precise statistical significance; every measurement was repeated several times. At the research, there was found out that the circular saw blade with uniform tooth spacing has lower equivalent noise level at smaller feeding speed and cutting soft wood species. The circular saw blade with non-uniform tooth spacing has lower equivalent noise level at higher feeding speed.

WOOD RESEARCH Volume 65, Number 5, 2020
Elena Nikolaevna Koptelova, Natalia Alekseevna Kutakova, Sergey Ivanovich Tretjakov, Anna Viktorovna Faleva, Evgeny Razumov, and Štefan Barcík

Extraction of betulin from the birch bark balance at pulp and paper production

The technical bark was used to obtain betulin; the one which is a barking of birch balance at pulp and paper production. The bark was prepared by grinding it on a crusher of abrasive action and fractionating, thus, the main fractions were obtained: less than 1 mm (35.4%), from 3 to 4.5 mm (31.5%). The bark was separated during the grinding process, the bark prevails in the coarse fraction, while bast is found in the fine fraction. For comparison, model samples of various sizes of birch bark were obtained by hand cutting. Chemical processing of bark fractions and model birch bark samples were carried out by the use of super-high frequencies (SHF) extraction with ethyl alcohol. Raw betulin was settled from extracts. The yield of extractive substances and raw betulin was 12.1-21.9% and 5.1-16.7% from absolutely dry raw materials; the maximum yield was from a coarse fraction of the bark or from model samples with smaller particle sizes. The authors studied the kinetics of the yield of extractive substances depending on the duration of SHF-extraction for bark fractions and birch bark samples. The optimal duration of the extraction for bark fractions is 10 min, and for birch bark is 15 min. The quantitative content was determined by the high performance liquid chromatography (HPLC) method for the obtained samples of betulin raw material. The total content of triterpenoids in the samples is about 80%, the betulin share is between 70.3 – 72.1%, from the absolutely dry substances of the extract. Coarse fraction of the bark contains more of the main component as compared to other fractions. It is advisable to use the fine fraction of the bark as a source of phenolic substances.

WOOD RESEARCH Volume 64, Number 3, 2019
Peter Koleda, Štefan Barcík, Ľubomír Naščák, Ján Svoreň, and Jaroslava Štefková

Cutting power during lengthwise milling of thermally modified oak wood

The paper presents experimental results of cutting power of thermally modified and non-modified hardwood of Summer oak (Quercus robur) during lengthwise milling. The process of heat treatment was performed in the atmosphere of superheated steam, at temperature 210ºC. Cutting power was determined during milling of the radial surface of modified and non-modified samples. It was calculated as the difference of power consumption by a milling machine during wood machining and at idling. Several cutting regimes were tested by combining different values of rotation speed, feed speed, rake angle and constant cutting depth ae = 1 mm. The values of cutting power are approximately the same at the kinematic angle of the tool head γ = 15°, 30°; there are bigger differences for γ = 20°. The decline of cutting power in the thermally modified (210°C) oak wood machining compared to natural oak wood is 21.7% ÷ 22.2% at the cutting speed vc =40 m. s-1.