Study washboarding phenomenon in frame sawing machines

The paper concerns washboarding phenomenon where for every kind of sawing a very regular pattern is characterised by a sinusoidal – like variation in board thickness. That pattern is an effect of the saw blade lateral vibrations. It is palpable that these vibrations are detrimental to the cutting process, and lead to poor surface quality and dimensional accuracy, and raw material waste. For band saws in the contemporary literature models explaining a washboarding phenomenon are supported on self-excited (self-induced) vibration theories. However, these explanations cannot be simply broadened into the washboarding phenomenon in frame sawing machines. In this work based on theoretical and experimental investigation the washboard pattern formation is clarified by the authors with the use of a theoretical model, in which the rugged surface is an effect of vibrations generated by lateral cyclic loading and lagged wave formation. The authors hope that their obtained results contribute significantly to further understanding of this important but complicated phenomenon.     

Study washboarding phenomenon in frame sawing machines

The paper concerns washboarding phenomenon where for every kind of sawing a very regular pattern is characterised by a sinusoidal – like variation in board thickness. That pattern is an effect of the saw blade lateral vibrations. It is palpable that these vibrations are detrimental to the cutting process, and lead to poor surface quality and dimensional accuracy, and raw material waste. For band saws in the contemporary literature models explaining a washboarding phenomenon are supported on self-excited (self-induced) vibration theories. However, these explanations cannot be simply broadened into the washboarding phenomenon in frame sawing machines. In this work based on theoretical and experimental investigation the washboard pattern formation is clarified by the authors with the use of a theoretical model, in which the rugged surface is an effect of vibrations generated by lateral cyclic loading and lagged wave formation. The authors hope that their obtained results contribute significantly to further understanding of this important but complicated phenomenon.     

Influence of mechanical properties and mineral salts in wood species on tool wear of high-speed steels and stellite-tipped tools – Consideration of tool wear of the newly developed tip-inserted band saw

This paper is the third in a series of work done on a novel technique for bandsawing, which uses a tip-inserted saw, and is gaining increasing popularity in Japan. It builds up on previous reports on the novel technique for bandsawing, which considered cutting tool hardness, tool wear, accuracy of kerf width, washboarding, and surface profiles of the workpiece. In this paper, ash content analysis and three-point static bending tests were conducted to clarify the influence of mineral salts and mechanical properties of wood samples of Elais guineensis (Oil palm), Strombosia glaucescens (Afina), and Cryptomeria japonica (Sugi) on cutting tool wear. The cutting tools were made from Stellite and High Speed Steels (HSS) of designations SUS420J2 and TiN coated SKH 51 according to the Japan Industrial Standards (JIS). Among the tested wood samples, the highest cutting tool edge recession when machining with SUS420J2 and TiN coated SKH 51 tools were recorded in Oil palm in spite of Afina possessing the highest mechanical strength properties. On the contrary, Stellite in spite of possessing the smallest hardness (HV580) among all the tested cutting tools recorded the lowest cutting tool edge recession when machining wood samples of Oil palm. However, Stellite recorded the highest edge recession when machining Afina, a high density species. Ash content analysis and a scanning electron micrograph of wood samples of the tested wood species show the presence of high proportions of mineral salts in the transverse, radial and tangential sections of Oil palm. This could perhaps account for the high cutting tool edge recessions recorded in wood samples of the Oil palm. The studies have demonstrated that silica accumulation species could have significant effect on tool wear of high speed steels.     

Experimental cutting on the table band-sawing mashine

This article presents the results of experiments, aimed at studying the influence of chosen technical and technological factors (cutting speed, width of saw band, cutting height, radius of sawing) on the side deflection of the saw band of a table bandsawing machine in curvilinear sawing. The contactless opto-elektronical method was used for observation. The light deflection of the reflected infrared ray from the tool was measured by means of a planar diode.     

Neue Plattenaufteilanlage bei Pfleiderer,Rheda

A large new board trimming plant is described considering its processing and machinery. Besides large-scale transportation techniques, the whole plant consists of the following: processing station for the head stripes; circular saws for longitudinal cuts mounted on a socalled saw-portal, the table bearing the piled boards travelling below the saw-portal, a cross-cut saw, sawing from underneath and two positioning bars. The maximum cutting height is 160 mm.     

On-line control of feed-speed in circular sawing

An adaptive control optimization system was developed to produce a desired surface finish roughness by automatic control of the work-piece feed-rate in circular sawing. The system developed in this study consists of the interconnection of an adaptive controller with a numerically controlled circular saw. The AE signals and cutting forces were measured to monitor the machining process continuously in this system. The signals were provided to the adaptive controller to evaluate the surface finish roughness and adjust the workpiece feed-rate automatically in the machining process. Sensing of AE signals and of cutting forces was compared to determine which technique is more convenient. Experiments were carried out with a carbide-tipped circular saw. Cross cutting was done with counter-cutting during the experiments. The cutting parameters controlled were workpiece feed-rates and cutting speeds. Japanese beech (Fagus crenata Blume) and Yezo spruce (Picea jezoensis Carr.) were used as the workpiece. Experimental results indicated that adaptive control optimization took place in the system developed for circular sawing. The desired surface finish roughness was produced by automatic control of the workpiece feed-rate using the sensing technique of AE signals as well as that of cutting force. However, the system using AE signals is more convenient than taht using cutting force.     

环形金刚石线锯切割大理石试验研究

选用环形电镀金刚石线锯切割大理石,分析了锯丝线速度、工件进给速度和锯丝张紧力对大理石表面加工质量的影响,研究了金刚石锯丝的磨损机理。结果表明：工件进给速度对大理石表面粗糙度的影响最大,锯丝线速度对大理石表面粗糙度的影响次之,锯丝张紧力对大理石表面粗糙度的影响再次之。在本试验参数范围内,最优工艺参数为：工件进给速度为10mm/min,锯丝线速度为30m/s,锯丝张紧力为100N。     

Effect of tooth front bevel angle on cutting accuracy and chip formation for cicular rip saws

When using sawdust in the pulp making process the wood fibres should be as long as possible. Circular saws with alternatively front or top beveled teeth produce saw dust with such characteristics. In this study the effect of bevel angle on cutting accuracy, surface finish, and saw dust quality was studied. A bevel angle of 15° maintained good cutting accuracy, produced good surface finish, and produced fibre quality superior to that obtained from saws with no bevel.     

一种高效长寿命混凝土锯片的研制

通过对混凝土的结构特点及其对金刚石圆锯片锯切的影响进行分析,对混凝土锯片的胎体配方设计、金刚石选用、锯片结构设计、焊接等技术进行探讨,研制出熟水泥锯片和生水泥锯片,并进行室内试验台锯切对比试验及施工现场使用。结果表明,这种锯片锯切效率高,使用寿命长,具有很好的市场前景。     

Influence of vibration coupling between bandsaw frame and feed-carriage system on sawdust spillage and surface quality of workpiece during sawing

Productivity, surface quality, and recovery are three parameters that compete for attention during lumber production. The well known phenomenon of improved surface quality with decreasing workpiece feed rate has been reported by several researchers. This paper reports on experimental results from the relationship between workpiece feed rate or bite per tooth and the surface roughness of Japanese Sugi (Cryptomeria japonica) using a bandsaw machine whose feed-carriage is coupled to the bandsaw frame. The volume of sawdust produced during sawing was determined using an electronic balance. Equation was developed to determine the kerf-losses. It was observed that as the workpiece feed rate increased, or as the bite per tooth increased, the saw blade vibration decreased and the volume of sawdust also decreased contrary to expected results. Furthermore it was observed that with increasing workpiece feed rate the surface roughness decreased contrary to expected results. On the other hand, when the carriage feed rate increased the saw blade deviation also increased as expected. The research findings clearly suggest that when there is vibration coupling between the feed-carriage and the entire bandsaw frame, the amplitude of the saw blade vibration and the surface roughness decrease as the bite per tooth increases. Thus the bandsaw machine whose frame is coupled to the feed-carriage is a promising technique for increasing lumber recovery and improving upon surface quality.     

木工带锯振动领域的研究发展

基于木工带锯机锯切稳定性与切削性能的考虑,本文通过对国内外木工带锯振动领域的研究进展综述,并提出加快我国木工机械理论研究和应用步伐的建议。     

Angewandte Problemlösungen beim Kreissägen in den USA

Reduction of kerf and sawing variation is one of the major concerns today in the sawmilling industry in the United States. Significant advances have been made during the last two decades towards the use of thin kerf (≦2.5 mm) accurate sawing through innovations in the design of the sawing machine, specifications of the saw blade and the sawing process, on-line saw vibration control and improved saw maintenance. The most significant accomplishments, for instance the application of critical speed theory, are discussed.     

圆锯片噪声产生机理及降噪技木

分析了圆锯片噪声产生的机理,同时指出共振噪声是圆锯片噪声的重要组成部分。根据增加圆锯片阻尼、改变圆锯片的共振频率及改变激振力频率可减小振动实现降噪的原理,本文主要分析了多层基体结构、开热胀槽及不等齿距等结构圆锯片的降噪技术。     

荒料开板工具存在的问题及新型工具的研制

首先比较了几种现有荒料开板工具的性能特点,分别计算了它们的锯切成本,从而分析了现有工具存在的问题。由此提出了将金刚石链锯应用于荒料开板的设想,并分析了这种新型荒料开板工具可能潜在的优势。     

Why are guided circular saws more stable than unguided saws?

This paper indicates why guided circular saws are typically more stable than similar unguided saws. It introduces lateral stiffness as a practical stability measure to quantify the ability of both circular saw types to resist lateral cutting forces without large deflections. Proper tensioning is shown to be very important as a means of maximizing sawblade stiffness. Previously used measures of sawblade dynamic stability, such as critical speed margin and lowest natural frequency, cannot adequately account for spatially dependent features such as guides, and can give, misleading stability comparisons.     

几种金刚石工具锯切石材分析

金刚石工具的圆锯片、绳锯和框架锯条，是目前最常用的石材加工工具，它们因为加工方式和锯切机理的巨大差异而相互补充，在石材加工中发挥着重要作用。文章分析了这些工具锯切石材时的受力和磨损情况，比较了其加工性能上的特点。以当前最具发展潜力而业内相对缺乏研究的绳锯为分析重点，认为这一加工方式具有许多独特和复杂的地方，不能用我们熟知的其它锯切机理进行简单的类推，并提出了一些新的看法。     

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.     

环线金刚石线锯机旋转切割的研究

对蓝宝石、晶体硅等贵重硬脆晶体加工的要求越来越高,如切割效率和表面加工质量,而且工件的尺寸也逐渐增大,需要设计一种高效的切割设备并探索新的切割方式。本研究建立了一种旋转切割模型,通过旋转工件进行切割,保持一种单点接触式的切割,提高环线金刚石线锯机的切割效率。利用自制的环形金刚石线锯机做切割实验,结果表明,相对于常规固定式的切割法,切割效率至少提高了50%,并且提高了表面加工质量。     

Aktive Geräuschminderung beim kreissägen

A number of measures can contribute towards noise abatement in circular saws which, when combined, result in a considerable reduction in noise level. The idling noise of circular saw blades is affected to a large extent by the geometry of the toothed rim, damping of blade trunk and circumferential speed. Cutting noise is predominantly related to damping of the tool and to wear. Investigations proved that a reduction in cutting speed, from the conventional 70 m/s to 50 m/s, results in a lessening of cutting noise. At the same time tool wear was reduced and edge quality improved.