Untersuchungen über das Bandschleifen von Holz mit geradliniger Schnittbewegung

Summary Tests have been made on a special belt sander to study some relations in wood sanding. Specimens of spruce, pine, poplar, alder, red beech, oak, and teak wood have been used as test material. The influence of various factors has been investigated by determination of the volume of abrased wood and the main cutting force. These factors are species of wood, direction of fibre, size of sanding area, belt speed, pressure, and grit sizes. Results: The volume of abrasion is influenced by structure, strength, and wood extractives and increases with sanding perpendicular to the grain. With constant pressure volume of abrasion increases in proportion to reduction of sanding area. The optimum belt speed as determined by the specific quantities of abrasion is 30 m/s for grit size 60 and slightly less than 30 m/s for grit size 120. The influence of grit size is mainly determined by smaller volumes of abrasion for finer grits and higher sensibility against high pressures.

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Mitteilung aus dem Versuchsfeld für Holzbearbeitung der Technischen Hochschule Braunschweig     

磨削木竹材表面粗糙度对胶合强度的影响

采用探针法测定了水曲柳、毛竹和落叶松砂带磨削表面的粗糙度,分析了影响表面粗糙度的因素,并采用心理分析方法讨论了的粗糙感与表面粗糙度关系;还分析了木材表面粗糙度对胶合强度的影响.为获得不同树种及不同粒度砂带磨削对工件表面粗糙度和粗糙感的影响,实验测量了磨削工件表面的粗糙度和粗糙感触觉心理量、视觉心理量.研究结果表明,材种和表面组织构造影响表面粗糙度;表面粗糙度值因为材种不同而不同,随着加工精度的提高而降低;水曲柳、毛竹和落叶松表面粗糙感的触觉心理量与视觉心理量呈正相关;阔叶材、竹材、针叶材表面粗糙感的触觉心理量与视觉心理量的相关性逐渐增大;触觉心理量与表面粗糙度参数的相关性要高于视觉心理量.砂带磨削木竹材表面的胶合强度在磨削砂带柱度为100～150目时达到最大值.     

基于田口法的木制品异形表面砂光参数优化研究

用条状刷式砂光方式对木材进行砂光实验,以加工工件表面粗糙度为优化目标,利用田口法对砂带目数、条状刷式砂轮转速、进给速度、理论接触长度、砂光次数等砂光参数进行优化,再根据试验得出多个因素不同水平的平均表面粗糙度和信噪比(S/N),利用SPSS软件进行实验结果分析,研究各砂光参数对表面粗糙度影响的显著性,得出最优砂光参数组合,并对此最优砂光参数组合进行了实验验证。     

Optimizing the abrasive sanding process of rubberwood (Hevea brasiliensis)

The abrasive sanding process is the most labor-intensive operation in the Rubberwood furniture manufacturing industry. Although the machining properties of Rubberwood (Hevea brasiliensis) are well established, information on its abrasive sanding characteristics is sparse. This study was carried out to establish the optimal abrasive sanding regime for Rubberwood. The results suggest that the abrasive sanding process can be optimized when well machine-planed Rubberwood stocks are used. Further, it was found that when the machine surface quality was good, abrasive sanding with a two-level sequence of grit sizes was sufficient to produce an acceptable surface smoothness. The improved surface smoothness also minimized the coating film spread on the wood surface. This finding will serve as a useful benchmark for machine-planing and abrasive sanding processes in the high-volume Rubberwood furniture manufacturing industry.     

The abrasive sanding of Rubberwood (Hevea brasiliensis): an industrial perspective

) as a raw material for high-volume furniture production, information on its sanding properties is relatively sparse. This study was carried out to provide some fundamental understanding of the sanding properties of the material, from an industrial perspective. The results suggest that the sanding process is suitable for low to moderate stock removal, for it ensures optimal process economics. Further, silicone carbide abrasive belts perform better than aluminum oxide abrasive belts for the sanding of Rubberwood. A simple method was used to estimate the economic belt life, which will help derive effective belt change schedules in order to enhance the productivity of the process.     

Employing artificial neural networks for minimizing surface roughness and power consumption in abrasive machining of wood

One of the biggest challenges in machining processes of wood is to detect the optimum values of process parameters for reducing the final production cost. In the present study, the effects of various process parameters on surface roughness and power consumption in abrasive machining process of wood using experimental data collected from the literature were modeled by artificial neural networks (ANNs). The results have indicated that accurate prediction of the experimental data by neural network models was achieved with the mean absolute percentage error (MAPE) less than 2.51 % for power consumption and 2.65 % for surface roughness in the testing phase. Besides, the values of determination coefficient (R²) were found as 0.994 and 0.985 in the prediction of surface roughness and power consumption by the ANN modeling, respectively. Based on the results, it can be said that by means of the proposed models the surface roughness and power consumption can easily be predicted with very high degrees of accuracy in abrasive machining process of wood. Consequently, the present study can effectively be applied to the wood industry to reduce the time, energy consumption and high experimental costs because it eliminates the need for a large number of experiments.     

木材磨削力和影响磨削力的因素

通过试验分析了磨削过程中砂带速度、砂带目数以及木材纹理方向对于磨削力、法向力和磨削过程中功率损耗的影响,研究表明:磨削力均值和砂带速度呈降幂变化规律,法向力均值和砂带速度呈二次幂变化规律,磨削力均值与砂带目数呈线性增加趋势,法向力均值和砂带目数呈二次幂变化规律。功率损耗和砂带速度呈二次幂变化规律,和砂带目数呈线性变化规律。其中顺纹理磨削过程中磨削力、法向力及功率最大,横纹理最小。     

Dust-generation characteristics of hardwoods during sanding processes

A study of the factors that influence dust-generation during the sanding process of Malaysian hardwoods was undertaken. It was found that the amount of wood removed during the sanding process predetermined dust-generation, although the wood density and abrasive grit used also played a role. Consequently, low density wood species produced higher dust-concentration due to its relative ease of sanding, and vice-versa. The results of the study suggest that minimizing dust-generation during the hardwood sanding process could be achieved by ensuring minimal amount of wood removal as well as the use of the coarsest possible abrasive grit in the process.     

Effect of thermal rectification on machinability of Eucalyptus grandis and Pinus caribaea var. hondurensis woods

Thermally rectified wood acquires colors similar to those observed in tropical woods, improved resistance to fungi and weathering, higher dimensional stability and lower hygroscopicity. Little information is available on the effect of heat treatments on the machining properties of wood. In this work, relatively low-valued woods (Eucalyptus grandis and Pinus caribaea var. hondurensis) underwent a variety of thermal rectification treatments (from 140°C to 200°C), performed in presence or scarcity of oxygen. Heat-treated wood underwent peripheral knife-planing (15°, 20°, and 25° rake angles) and sanding tests (60?C80, 80?C100, and 100?C120 grit). Surface quality was evaluated as a function of the incidence of machining defects and uniformity of texture (planed surfaces), and roughness and wettability (sanded surfaces). Thermally rectified samples provided better surface quality after planing, and increased surface roughness after sanding, compared to control samples. The increment of treatment temperature caused an increase in wetting time, which indicates reduced hygroscopicity.     

Effects of cutting parameters on surface quality of paper birch wood machined across the grain with two planing techniques

Helical planing and face milling were applied across the grain to surface paper birch wood prior to coating application. Three feed speeds and three cutting depths were evaluated for face milling while three cutting depths were studied for helical planing. The roughness and wetting properties of wood as well as pull-off strength of a solvent-borne coating after aging were evaluated. For helical planing, no significant effects of the cutting depth on roughness and wetting properties were found. For face milling, the cutting depth had no significant effect on the surface roughness while it had a significant impact on the wetting properties. The feed speed affected significantly both parameters. Furthermore, none of these parameters had a significant effect on the pull-off strength. However, helical planing produced smoother surfaces with equivalent wetting properties and higher pull-off strength than face milling. Scanning electron microscopy showed more exposed cell lumina and sound cells for helical planed surfaces, which enhanced their wetting and adhesion properties.     

木材刷式砂光机砂光参数的选择(2)

以刷式砂轮砂光试验机为砂光设备,以砂轮转速、进给速度、砂光次数为砂光参数,测量砂光参数与表面粗糙度Ra之间的关系,得出了在本实验条件下较理想的砂光条件.     

The abrasive sanding of Rubberwood (Hevea brasiliensis): an industrial perspective

Hevea brasiliensis ) as a raw material for high-volume furniture production, information on its sanding properties is relatively sparse. This study was carried out to provide some fundamental understanding of the sanding properties of the material, from an industrial perspective. The results suggest that the sanding process is suitable for low to moderate stock removal, for it ensures optimal process economics. Further, silicone carbide abrasive belts perform better than aluminum oxide abrasive belts for the sanding of Rubberwood. A simple method was used to estimate the economic belt life, which will help derive effective belt change schedules in order to enhance the productivity of the process.

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Bonding surface-modified Karri and Jarrah with resorcinol formaldehyde

A series of abrasive papers were used to sand machined regrowth karri (Eucalyptus diversicolor) and regrowth jarrah (E. marginata) wood surfaces. Shear test specimens were then prepared by gluing sanded wood blocks with resorcinol-formaldehyde and pressing them at 1500 kPa and 20°C for 7 hours. Wettability measurements on sanded wood surfaces and strength tests on shear test specimens were used to assess the ability of the sanding treatment to improve adhesive performance. The effect of sanding on wettability and shear strength varied according to the abrasiveness of the sanding treatment. Application of the coarsest abrasive (80 grit) significantly improved wettability and shear (adhesive) strength in both dry and wet conditions. A positive correlation between wettability and shear strength occurred only after sanding. SEM observations revealed different morphological structures of the glueline in sanded and non-sanded surfaces.     

Visual and visuo-tactile preferences of Malagasy consumers for machined wood surfaces for furniture: acceptability thresholds for surface parameters

In wood machining operations, target surfaces are chosen to achieve technical functions (gluing, finishing), or aesthetic functions (raw wood, varnishing) in order to produce a surface which consumers will appreciate. Although the literature often refers to the optimization of cutting conditions to improve the surface quality, there is currently no specific criterion to define what good surface quality is. The purpose of this study was to investigate quantitative criteria related to consumer preferences and to find an acceptability threshold for each criterion in order to determine the best cutting conditions. To this end, 32 surfaces from Chrysophilum boivinianum (Sapotaceae) were machined in various cutting conditions which yielded surfaces ranging from very rough to smooth. The primary surface profile, roughness and waviness parameters, and machining defects (raised grain, torn grain, chip marks, cutting traces) were measured on each surface. Visual and visuo-tactile tests were then carried out with a panel of 174 consumers. The results show that touch allowed better appreciation of surface defects than a simple visual observation. Consumers like smooth surfaces without visible defects and less visible peaks of waviness. The acceptability thresholds of surface parameters correlated with consumer preferences were determined. The rotational speed and the feed speed affect the most the surface quality. To obtain good surface quality for consumers, the rotation speed should be greater than 5000 rpm, with a maximum feed rate per tooth of 0.5 mm, and a maximum average chip thickness of 0.18 mm. This knowledge will help industries to better optimize the cutting of wood.     

Effect of drying method on the surface wettability of wood strands

An experiment was conducted to investigate the effects of drying methods, namely rotary drum, lab oven, microwave and air-drying, on the surface wettability of wood strands by the Wilhelmy plate method. The measurements included the surface contact angle, free energy, and liquid sorption capacity. Thirty industrial strands including southern yellow pine (Pinus spp.) and poplar (Populus spp.) were randomly collected for each drying method. The results from this study showed that the surface contact angle of a strand depends on the liquid used as well as the drying method and wood species. Liquid sorption capacity of the pine strands increased with decreasing surface contact angle, but this trend was not observed with the poplar strands. The total surface energy was almost the same for strands within species, regardless of the drying method, but it was higher on poplar strands than on pines. The polar and disperse components of surface free energy varied with both drying method and wood species. The surface polar energies of oven-dried pine strands and rotating drum-dried poplar strands were higher than on strands dried by other methods. For lower temperature drying methods (air and microwave), the lowest polar component was observed on the radial face of the pine strands. For the higher-temperature drying methods (oven and rotary-drum), the lowest polar component was found to on the tangential face of the pine strands.     

Machining qualification of solid wood of Fagus silvatica L. and Piceaexcelsa L.: cutting forces, power requirements and surface roughness

Fagus silvatica) and spruce (Picea excelsa). The machining process was carried out on a shaper with specific devices. The concerned variables were: cutting depth, feed rate and cutting speed. The mean chip thickness and cutting width were constant. The machining process was done in two different ways: conventional and climb cutting; thus it was possible to compare both working directions with the same machining parameters and watch their influence on the cutting forces, the power consumption and the surface roughness. The most important variables on the cutting forces are depth of cut, wood density and feed direction. With regard to power consumption, it was detected that the most important variables were cutting speed, feed direction, depth of cut and wood density. It was further demonstrated that the measured and calculated power have a very good correlation, and that the cutting forces can be determined by the calculated power. Thus, if cutting power is measured for a specific condition of wood and machine, the cutting forces can be estimated. The surface roughness was very homogeneous in all the tests. The better machining process was obtained when applying conventional cutting. Then the cutting forces, the power requirements and the roughness standard deviation reach smaller values.

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Fagus silvatica ) und Fichtenholz (Picea excelsa). Der Bearbeitungsprozess erfolgte auf einer speziellen Holzhobelmaschine. Die relevanten Variabeln waren: die Schnitttiefe, der Vorschub und die Schnittgeschwindigkeit. Die mittlere Spanst?rke und die Schnittbreite waren konstant. Die Bearbeitung wurde auf zwei verschiedene Arten durchgeführt: im Gleichlauf und im Gegenlauf, somit war es m?glich, beide Bearbeitungsrichtungen unter Beibehaltung der Parameter zu vergleichen und ihren Einfluss auf die Schnittkr?fte, den Leistungsbedarf und die Oberfl?chenrauhigkeit zu prüfen. Die wichtigsten Einflu?variabeln bezüglich der Schnittkr?fte waren die Schnitttiefe, die Materialdichte und die Vorschubrichtung. Den Leistungsbedarf betreffend kamen wir zu dem Ergebnis, da? sowohl die Vorschubrichtung, die Materialdichte als auch die Schnittkr?fte, -geschwindigkeit und -tiefe die Haupteinflu?faktoren waren. Es konnte gezeigt werden, da? die gemessene und berechnete Leistung gut korreliert sind, und da? die Schnittkr?fte mittels der berechneten Leistung bestimmbar sind. Es ist daher m?glich, durch Messen des Leistungsbedarfs einer Bearbeitung einer bestimmten Holzart auf einer definierten Maschine die Schnittkr?fte abzusch?tzen. Die Oberfl?chengüte war gleichbleibend in allen durchgeführten Versuchen. Die besten Versuchsergebnisse wurden in Gegenlaufbearbeitung erzielt. Die Schnittkr?fte, der Leistungsbedarf und die Standardabweichung der Oberfl?chenrauhigkeit erreichen hier jeweils ihre Minimalwerte.

     

Surface roughness in sapwood and heartwood of Blackwood (Acacia melanoxylon R. Br.) machined in 90-0 direction

The resulting surface roughness is studied for Blackwood (Acacia melanoxylon) during peripheral milling of sapwood and heartwood samples. It is known that the surface roughness is sensitive to a change in cutting conditions, tool wear, cutting geometry and direction change, but also when some material parameters vary like the species, moisture content and wood density. The bite or better the mean chip thickness is strongly related to the resulting surface quality as well as to the needed cutting forces, whereas other studies have shown these relationships with regard to changing cutting conditions. The aim of this paper is to evaluate and quantify the resulting surface roughness for Acacia melanoxylon considering a change in the mean chip thickness for both types of wood: sapwood and heartwood, and to evaluate the results considering changes in the rotational speed and the feed speed.     

Effect of species and grinding disc distance on the surface roughness parameters of medium density fiberboard

Surface quality of medium density fiberboard (MDF), as a very important criterion for further finishing and utilization, was evaluated using a wide range of measuring parameters (instruments, filters, filtering cut-off length, measuring length, measuring resolution, roughness parameters). However, these various approaches make any data comparison rather difficult. Furthermore, filtering the measured data with a simple Gaussian filter has proved unreliable for wood surfaces. A new, more robust approach by using a Robust Gaussian Regression filter together with a previously tested set of measuring and evaluating parameters was used in this paper in order to quantify the surface roughness of MDF manufactured from different species (beech, poplar, birch, Scots pine, mixture 50 % Scots pine and 50 % beech) and using three different grinding disc distances (0.06, 0.15 and 0.6 mm). If manufacturing parameters are kept constant, the processing roughness of MDF is similar, but variable species anatomy and fuzziness effects will give differentiation in total roughness. The results indicated that fibers made of a mixture of wood chips from Scots pine and beech led to the smoothest MDF surface, followed closely by poplar, birch, and Scots pine. The roughest surface was measured for the panels made of beech fibers. Investigating the influence of the grinding disc distance, the roughest MDF surface was obtained when a grinding gap of 0.6 mm was used. However, surface roughness was found to be quite similar applying a grinding disc distance of 0.06 mm slightly lower for 0.15 mm. This finding indicates that a too fine grinding gap does not improve the MDF surface roughness.     

Filtering the roughness of a sanded wood surface

Any quantitative evaluation of the roughness of a sanded surface requires that the data is filtered to remove form errors and waviness. The cut-off length of a roughness filter is the valuethat determines which wavelengths are to be removed from profile data. Wood surfaces contain irregularities due to both the sanding process and the anatomy. When this anatomical roughness is greater than the roughness due to processing, standard profile filters introduce distortions, which increase in magnitude when a short cut-off length is used. Wood anatomical irregularities overlaid on processing irregularities would render standard recommendation in selecting cut-off length unreliable. This paper investigates the influence of the cut-off length of the filter on roughness parameters of sanded solid wood, when the surface is filtered with a robust Gaussian Regression filter. This filter should give roughness profiles free of distortions if the cut-off length is properly selected. For grit sizes P120 to P180, which commonly precede finishing applications, a 2.5 mm cut-off value was found suitable. However, finer processing with P1000 required larger cut-off lengths to overcome the distorting effect of grouped pores.     

Influence of spinning parameters on milkweed/cotton DREF-3 yarn properties

In this study, Pergularia milkweed fibre (70%), cotton fibre (30%) core and 100% cotton fibre sheath DREF-3 core yarns of 74?tex were produced using different spinning parameters in order to understand their effect on yarn properties. Box–Behnken design was used for the optimization of core ratio, drum speed and suction pressure, and to evaluate the effects and interactions of the process variables on the yarn properties at a constant opening roller speed of 12,000?rpm and production speed of 100?m/min. The effects of the core/sheath ratio on all the yarn properties are significant. With an increase in the core/sheath ratio, yarn tenacity and elongation decrease due to insufficient wrapper fibres in the yarn and yarn unevenness; imperfection increases due to higher feed rate and draft at higher core ratio. The yarn hairiness increases at higher core ratio due to higher number of short fibres in milkweed and lesser sheath fibres to cover the core fibres effectively. An increase in the spinning drum speed damages fibre in the sheath and increases the number of hooks at the end of fibres, as a result of which the core yarn tenacity decreases at higher drum speed. At a higher air suction pressure, yarn tenacity and the elongation at break increases. The drum speed and suction pressure have no significant effect on yarn unevenness and imperfections. The yarn hairiness decreases slightly with increase in drum speed and suction pressure but is insignificant.