Valovitost bukovega rezanega furnirja

V lesni industriji je plemeniti furnir izdelek z visoko dodano vrednostjo. Tehnološki proces izdelave je razmeroma dobro poznan, vendar na kakovost izdelanega furnirja in posledično ceno vpliva veliko tehnoloških parametrov izdelave, največji vpliv pa ima kakovost hlodovine. V raziskavi smo preučili vpliv optičnih napak bukove (Fagus sylvatica L.) hlodovine in vpliv klimatskih razmer v fazi sušenja rezanega furnirja na valovitost površine. Raziskava je bila opravljena v industrijskem okolju. Rezultati kažejo, da je bilo procentualno največ valovitega furnirja izrezanega iz razpokanega hloda (71 %), najmanj pa iz ukrivljenega hloda (20 %). Kakovostno razvrščanje furnirja je bilo ročno in po subjektivnem kriteriju izkušenih kontrolorjev iz industrije. Kljub njihovim izkušnjam pa lahko subjektivna ocena vpliva na natančnost razvrščanja in s tem na rezultate raziskave. Zato smo preučili tudi možnost integracije 3D kamere za merjenje valovitosti furnirja in razvrščanje furnirja v kakovostne razrede.In wood industry, decorative veneer is a product of high added value. Although the technological process of sliced veneer is well known, its quality and price depend on many technological parameters of production, particularly on the quality of logs. The research, which was focused on the influence of visual defects of beech (Fagus sylvatica L.) logs and the impact of climatic conditions in the drying phase of sliced veneer on the surface veneer waviness, was conducted in an industrial environment. The results indicate that the largest share of waved veneer was cut from cracked logs (71%) and less from curved logs (20%). The veneer was sorted manually by experienced controllers from this branch of industry. Their subjective criteria can affect the accuracy of classification of veneer and, consequently, the research results. Therefore, the possibility of using 3D camera for measuring veneer waviness and grading the veneer into quality classes was examined

Situation of the Slovenian Sawmill Sector in 2013/2014

The Slovenian sawmill industry has undergone numerous changes since the beginning of economic crisis in 2008, mainly due to the decline in production in the furniture and construction industry. Consequently the sawmill sector struggled for survival instead of investing in new technologies and implementing innovations. In the framework of the international IDWOOD project (taking place between 2012 and 2014), aiming to promote and foster innovation and competitiveness of SMEs in the wood sector in the SEE area, an analysis of the Slovenian sawmill sector was carried out in order to identifying major gaps. Concurrently similar analysis was also carried out in the neighbour regions of the SEE area (i.e. Croatia, Bosnia and Herzegovina and Serbia). In the current article we would like to present the findings of the performed study. The results were compared with the situation of the sawmill industry in other SEE regions and advanced European countries

Monitoring the Quality and Quantity of Beechwood from Tree to Sawmill Product

The analysis evaluates the potential and methods of the respective assessment of beech trees, beech logs and sawn timber. The objective of the study was to assess the impact of the quality of the incoming raw material (tree) on the quality and quantity of products – obtained at the sawmill. The study presents a model that indicates the relations between the assessment of the quality of a standing beech tree and the quality of the sawmill products obtained from its wood. In addition, relations between individual quality classes of sawlogs, pulpwood, energy wood and sawn timber are shown. Standing trees were assessed in three sites according to the national 5-grade quality scale, assortments produced from selected trees pursuant to the EN 1316-1 standard, and sawn timber produced from assortments according to the rules of the European Organisation of the Sawmill Industry (EOS). In total, 87.04 m3 of timber was harvested. In higher quality trees (quality 1 and 2), the shares of sawlogs were between 53% and 72% of gross tree volume, but in the poorest quality trees, the shares were only between 23% and 36%. What remained was pulp and energy wood. In trees of excellent quality (quality 1), sawlogs of the highest quality prevailed (A and B quality grade), while sawlogs of C and B quality prevailed in trees of lower quality. Covered knots and heart defects were typically the decisive criteria for classifying sawlogs quality in all three sites. A total of 30,786 m3 of unedged timber was sawn from the sawlogs, which comprised 35% of the total gross quantity of trees on average. Nine percent of the sawn timber was classified into the A–EOS class (top quality), 27% into the B–EOS class and 47% into the C–EOS class. Seventeen percent of the timber was only suitable for post-processing. The crucial criteria for classifying sawn timber were as follows: dead and rotten knots, heart, curvature and cracks. Above-average sawlogs (A and B quality grade) was mainly obtained from trees of better quality. Relations between the quality of trees, sawlogs and sawn timber indicated the suitability of classifying standing trees and sawlogs, since it was possible to produce sawn timber of higher quality from quality trees or logs. The model presents a rare attempt to establish and monitor quality and quantity from standing tree to end product

Beech wood - correlations between the quality of trees, logs and sawn wood

V raziskavi smo preučevali količinsko-kakovostni izkoristek bukovine od stoječega drevesa do žaganega lesa. Zanimala nas je ocena kakovosti posameznih dreves in njen vpliv na kakovostne razrede proizvodov iz tega lesa. Pri razvrščanju stoječih dreves smo upoštevali aktualno 5-stopenjsko lestvico ocenjevanja kakovosti Zavoda za gozdove Slovenije (ZGS). Pri ocenjevanju gozdnih sortimentov smo uporabljali standard SIST EN 1316-1:2013, pri ocenjevanju žaganega lesa pa pravila Evropskega združenja žagarske industrije (EOS). Na vzorcu ocenjenih in nato posekanih dreves smo ugotavljali povezave med kakovostjo dreves, iz njih izdelanih sortimentov okroglega lesa in kakovostjo končnih žagarskih izdelkov. V vzorec so bila enakovredno zajeta drevesa vseh petih kakovostnih stopenj. Pri izdelavi gozdnih sortimentov smo dobili največ hlodov B-kakovosti (51 %) in največ žaganega lesa EOS-C-kakovosti (52 %). Iz bukovih dreves odlične kakovosti smo dobili 35 % najkakovostnejših sortimentov in iz teh sortimentov 8 % najkakovostnejšega žaganega lesa. Odločilni kriterij razvrščanja po kakovosti so pri sortimentih okroglega lesa slepice in pri žaganem lesu mrtve in trhle grče.The research addresses beech wood, from a standing tree to sawn wood. It focuses on the quality evaluation of individual trees and its impact on the later products made of the respective wood. For the needs of observing the quality of standing trees, the current 5-class scale for quality evaluation of the Slovenia Forest Service (SFS) was used. To evaluate the wood assortment, the SIST EN 1316-1:2013 standard was applied, while the evaluation of sawn wood was performed as per the rules of the European Organisation of the Sawmill Industry (EOS). On the basis of the sample of evaluated and eventually harvested trees, the correlations between the quality of trees, roundwood products made of them and the quality of final sawn products were established. The sample equally included trees of all five quality classes. The production of wood assortment provided the most logs of B quality (51%) and the highest quantity of sawn wood of EOS-C quality (52%). Beech trees of excellent quality provided 35% of the wood assortment of highest quality and these provided 8% of the sawn wood of the highest quality. The key criteria for the classification by quality were covered knots for forest products and dead and unsound knots for sawn wood

Faktor kritičnog intenziteta naprezanja (I. mod) bukovine (Fagus sylvatica) u TL presjeku: usporedba različitih metoda

The paper presents a comparison between various methods of mode I critical stress intensity factor KIC calculations of beech wood in the TL configuration. The first method is the stress intensity factor extrapolation to the distance of 0 mm from the crack tip; the second method is the use of the J integral; and the third method is based on the differences in deformation energies from which the strain energy release rate per unit of crack propagation length was obtained. The fourth method is the calculation of material deformation around the crack or the displacement of the triangle element node; and the fifth method uses a generally known equation for the CT specimen for plane-strain conditions in isotropic material. Using the finite element method, it was found that the J integral was least sensitive to the size and shape of the elements. It was used to calculate the critical stress intensity factor KIC for beech wood in a TL configuration. The average value is 0.56 MPa√m with a standard deviation of 0.047 MPa√m.Rad donosi usporedbu različitih metoda izračuna faktora kritičnog intenziteta naprezanja (mod I.) KIC za bukovo drvo na tangencijalno-longitudinalnom (TL) presjeku. Prva je metoda ekstrapolacija faktora intenziteta naprezanja na udaljenosti 0 mm od vrha pukotine, druga je primjena, J integrala a treća se metoda temelji na razlikama energija deformacije iz kojih je dobivena brzina oslobađanja energije deformacije po jedinici duljine širenj pukotine. Četvrta metoda temelji se na izračunu deformacije materijala oko pukotine ili pomaka vrhova elementa trokuta, a peta se koristi općepoznatom jednadžbom za CT uzorak za deformaciju u ravnini izotropnog materijala. Koristeći se metodom konačnih elemenata, utvrđeno je da je metoda J integrala najmanje osjetljiva na veličinu i oblik elemenata. Ta je metoda primijenjena za izračun faktora kritičnog naprezanja KIC za bukovo drvo na TL presjeku. Dobivena je prosječna vrijednost od 0,56 MPa·√m, sa standardnom devijacijom od 0,047 MPa·√m

Lesni sekanci - pomembna oblika biomase v Sloveniji

Slovenia has committed to achieve a 25% share of energy from renewable sources in the structure of final energy consumption by 2020. Wood biomass, besides hydropower, is the most important part of renewable energy in Slovenia. Despite the fact that the use of wood biomass is traditional and has become increasingly important in recent years, there is still a lot of uncertainty about insufficient production in the sale as well as in the purchase of various categories of wood biomass. The article presents information on the changed criteria for wood chips of different quality, in accordance with the current standards. We also studied various ways of trading wood chips and pointed the strengths and weaknesses of each. With a survey we wanted to find out the current trading pattern of wood chips and implementation of wood chip quality control in larger boiler plants in Slovenia. We have found that most-used trading method of wood chips is on the basis of volume, and that the quality control of wood chips is not systematically performed

Dodana vrednost v izdelkih v gozdno-lesni verigi - Primer: primarna predelava bukovine

The potential of wood raw material in the Slovenian forest wood supply chain is often insufficiently exploited. The promotion of its more rational use, while having indirect effects on the wider economic environment, is necessary to: (1) ensure the effective functioning of the entire forest wood supply chain, providing products with high added value; and (2) fully exploit the potential of wood raw material in terms of quality. In the article we examined added value of beechwood products, identified key challenges in this evaluation, and the relationships with other economic indicators that affect business decisions. Beechwood products were classified according to the amount of value added, and thereby the potential of beechwood raw materials was demonstrated in terms of both the impact on society and economic development. We thus confirmed the importance of the development and operation of the entire forest wood supply chain, and the importance of government economic policy in its functioning. More specifically, the state of primary wood processing as an important part of forest wood supply chain in Slovenia was examined, and some reasons for its ineffectiveness were identified. The availability of raw materials based on quality and purpose of use, and the value added per cubic meter of beechwood, were assessed in order to prove the reasonableness of investments in the newest technologies for hardwood processing and veneer production

Influence of Tool Wear on the Quality of the Newly Formed Surface in the Drilling of Wood Composites

The geometry of a drilling tool largely affects the quality of the newly formed surface. When drilling through a composite panel, the hole edge quality on the outlet side is significantly worse than on the inlet side, so the choice of the appropriate tool geometry is crucial. Even if the tool geometry is correct, tool wear also has a strong influence on the quality of the newly formed surface of the holes. With the tool wear, the force in the direction of drilling and torque around the axis of drilling are increasing which can affect to the delamination of particle board on the outlet side. The proposed model for hole edge quality prediction on the outlet side was tested on an experimental model where the cutting forces and torque in the drilling direction were measured, and the quality of the newly formed surfaces was evaluated every 180 holes using a visual method

Utjecaj radijalnih utora na dinamičku stabilnost termički napregnutog lista kružne pile

The influence of temperature distribution, temperature difference between the rim and centre of the saw blade and the number and size of radial slots on the dynamic stability of the circular saw blade was analysed in this work. The optimum number and size of radial slots for a circular saw blade with a diameter of 300 mm and a thickness of 2.18 mm is determined according to the least favourable temperature distribution and temperature difference. The critical rotational speed and lateral stiffness at the rim of the saw blade are considered as criteria for dynamic stability. According to the mentioned criteria, it was found that the optimum number and length of radial slots is 6 and 30 mm, respectively. In some cases, longer radial slots would further increase the critical rotational speed, but would also greatly decrease the lateral stiffness of the saw blade.U radu je analiziran utjecaj raspodjele temperature duž radijusa lista pile, temperaturne razlike između ruba i središta lista pile te utjecaj broja i veličine radijalnih utora na dinamičnu stabilnost kružne pile. Optimalan broj i veličina radijalnih utora za kružnu pilu promjera 300 mm i debljine 2,18 mm određuje se prema najmanje povoljnoj raspodjeli temperature i temperaturnoj razlici. Kritična brzina vrtnje i lateralna krutost na rubu lista pile smatraju se kriterijima za dinamičku stabilnost. Prema navedenim kriterijima, utvrđeno je da je optimalan broj radijalnih utora šest, a duljina radijalnih utora 30 mm. Dulji radijalni utori u nekim bi slučajevima dodatno povećali kritičnu brzinu vrtnje, ali bi se uvelike smanjila lateralna krutost pile