Surface roughness evaluation in medium density fibreboard rip sawing

Wood/panel specific gravity is a factor that has to be evaluated in the machining process because it affects the cutting forces behavior, plays an important role in the tool wear mechanisms and it is closely related to the surface roughness of the manufactured product. In the case of medium density fibreboard (MDF), which compared to solid wood is a homogeneous wood product, it is recognized that the specific gravity varies regularly across its profile, and these variations generate an uneven surface quality at the edge of the panel when machined. Among the operational parameters affecting the quality of the new surface, the cutting process kinematics is one of the most important parameters, namely the cutting speed and the chip thickness. In MDF industrial rip sawing operations, climb cutting and conventional cutting are additional parameters that affect the cutting quality. The objective of this study was to assess the surface roughness across the MDF panel profile produced by the rip sawing operation and to study the effect of cutting speed, mean chip thickness and cutting direction. The findings lead to the conclusion that low levels of surface roughness are reached when the cutting speed is increased at even higher feed speeds, particularly at the edge of the board. High correlation coefficients were found between mean chip thickness and surface roughness for both cutting directions. Finally, the specific gravity variation within the profile of the panel explains very well the resulting surface roughness found.     

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。     

Einfluß der Planlaufabweichung von Kreissägeblattschneiden auf den Zerspanvorgang

Cutting experiments with melamine-coated particleboards show to what extent axial run-out of the edges of carbide tipped circular saw-blades affects tool wear, cutting forces and the roughness of the workpiece edge. For protruding edges the effect on wear was greater than for receding ones. The same was true for passive forces. Saw-blades with minor axial run-out of the edges gave better quality work pice edges (less roughness of the cut surface) and had consid-erably longer service periods than blades with greater axial run-out. A new sharpening method and a suitable device were developed for sharpening sawblade edges, independently of axial run-out of the blade body. By this method circular sawblades can be produced with extremely low axial run-out of the blade edges.     

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.     

Application of a novel technique for band sawing using a tip-inserted saw regarding surface profiles

One way of achieving a successful forest management leading to biodiversity conservation is to ensure that wood is processed in an efficient manner. The authors succeeded in developing a new technology for bandsawing using a tip-inserted saw. The material used for the tipped edge was High Speed Steel (HSS) of designation SHK 51 according to the Japan Industrial Standard (JIS). The efficiency of the tip-inserted saw was investigated considering its effectiveness in controlling tooth marks and washboarding patterns that sometimes occur during bandsawing. The surface profile of the workpiece generated after sawing with 700 mm and 1100 mm diameter bandmills of the laboratory and industrial type respectively were determined using a CCD laser displacement sensor of scanning length 250 mm and scanning speed of 3 mm/sec at a sampling rate of 50 Hz. Under a setup wheel rotation speed of 200 rpm and feed speed of 1 m/min, washboardings were induced during sawing with the tip-inserted saw of uniform pitch. Thereafter, a tip-inserted saw of random pitch was constructed without removing the saw from the pulley and cutting tests were performed under the same cutting conditions when washboardings were induced during sawing with the uniform pitch tipped-inserted saw. It was observed that the washboarding pattern disappeared completely. Thus the tip-inserted saw of random pitch was very effective in controlling the washboarding pattern. Comparisons of the surface profiles of the workpiece generated by sawing with uniform pitch tip-inserted and stellite-tipped saws under both laboratory and industrial conditions indicate that regardless of the type of bandmill used, the surface profile measured with the laser displacement sensor was smoother for tip-inserted saws than stellite-tipped saws.     

径切板数控双联圆锯机的设计

分析了原木径切板制材的几种方法,提出了圆锯梯形下锯法的锯切原理,论述了径切板数控双联圆锯机的总体设计方案、结构组成、锯切装置和原木夹紧装置的设计要点,解释了双联圆锯机的主要技术参数.     

Influence of the manner of excitation of a machining system on the stability of the process of periodic circular cutting of wood tissue

The article deals with dynamic analysis of the influence of the manner of excitation of a machining system on the stability of the process of periodic circular cutting of wood tissue at an invariable frequency of cutting, taking into account dynamic properties of the machining system. For stability analysis we used a dynamic model developed for this purpose (Bu?ar and Kopa? 1996). The manner of excitation of the machining system has been defined by the radial immersion of the tool and the workpiece, taking into consideration, in modelling the process of cutting, both internal and external modulation of the cutting or exciting force. The internal modulation is the result of the effect of the properties of the machined material which are given by specific cutting pressurek _s, while the external modulation is the consequence of the varying material flux which is affected by relative displacements between the workpiece and the tool. Relative displacements, which are the result of the manner of excitation and dynamic properties of the machining system, are also the cause of self-excitation occurence. The results of analyses point to it that the manner of excitation of a machining system with known dynamic properties is of the essence for the stability of the process of periodic circular cutting of wood tissue.     

Cutting energy and surface roughness in medium density fiberboard rip sawing

Medium density fiberboard (MDF) is a?wood based panel which main feature is the distribution of wood fibers, uniform and dense in the full panel thickness, allowing for very precise machining on the edges and in the faces of the board. However, and due to its manufacturing process, a?density profile is produced with external layers being heavier than the core of the panel. These differences generate a?variable surface quality across the panel when machined. The tool characteristics and the cutting process kinematics also determine the resulting surface roughness of the processed material. With regard to the cutting energy, there are important variations when machining conditions are modified, or when some tool characteristics are changed. The aim of this paper is to determine the cutting energy required to rip sawing MDF and to study its relationship with the resulting surface roughness across the panel profile when the density of the material changes. The findings lead to the conclusion that there is a?close relationship between cutting energy and surface roughness, being particularly sensitive to changes in specific gravity within the profile of the panel, and in particular to changes in cutting condition expressed as mean chip thickness.     

Dynamic model for the determination of instability of periodic circular cutting of wood tissue

Shown is a dynamic model of periodic circular cutting of oriented wood tissue in which both the properties of the material and the dynamic properties of the machining system have been considered. The cutting or exciting force is the result of internal and external modulation. The internal modulation is the result of the effect of the properties of the machined material which are given by specific cutting pressure k _s, while the external modulation is the consequence of the varying material flux which is affected by relative displacements between the workpiece and the tool. Relative displacements, which are the consequence of the manner of excitation and dynamic properties of the machining system, are also the cause of self-excitation occurrence. As in the process of cutting, the cutting or self-exciting force depends on relative displacements between the tool and the workpiece, the dynamic model developed is non-linear. By simulation of a dynamic model it is possible to analyse the process of cutting wood tissue in its entirety, and it can thus be employed to optimize the selection of tools and the processing parameters of machining.     

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。     

数控木工曲线带锯机的研制

介绍了研制开发的MJKS365型数控木工曲线带锯机的工作原理.采用锯机连同带锯条一起以带锯条工作边锯齿齿尖连线为中心作回转摆动的方法,实现带锯条始终沿着锯切曲线的切线方向进行锯切.并依此设计了结构形式和数控系统.     

Hertmetall-Kreissägeblätter im Arbeitseinsatz

Zusammenfassung Der Einsatz von Hartmentall-Kreiss?gebl?ttern in der holz- und kunststoffbearbeitenden Industrie dient vor allem der Rationalisierung des S?gevorganges. In der vorliegenden Arbeit werden zun?chst die haupts?chlichen Arbeitsweisen des S?gens und die Einflüsse auf die Schnittgüte beim Trennen dargestellt. Zu diesen Einflüssen z?hlen als wichtigste die Zahnform siwie die Zahnabmessungen und die Z?hnezahlen der S?gebl?tter. Entsprechende Werte sind in Tabellen angegeben. Auch die Schnitteife. die Schnittbreite, die Vorschub- und die Schnittgeschwindigkeit sowie der Schneidenüberstand beeinflussen den S?gevorgang. Für sie werden Arbeitsrichtwerte angegeben. Schlie?lich wird in Rechenbeispielen der Leistungsbedarf ermittelt und die algemeinen Betriebsbedingungen dargestellt, die ein einwandfreies Arbeiten mit, Hartmetall-Kreiss?gebl?ttern erm?glichen.

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The use of hardalloy-tipped circular saw blades

Summary The use of hardalloy-tipped circular saw blades in the wood working industry mainly serves as economic measure in the sawing process. This paper first of all describes the most important sawing methods and the influences on the quality of cut during trimming. As particularly important influences the shape of tooth as well as the tooth dimensions and the number of teeth of the saw blades should be noted. The respective data may be obtained from the tables. Also of influence on the sawing process are the depth of cut, the cutting width, the feed speed, the cutting speed as well as the protrusion of the edge. Their coefficient data are quoted. Finally, the power demand is determined in mathematical, examples and the general working conditions which render possible the exakt working with hardalloy-tipped circular saw blades are described.

     

PcBN刀具在硬态切削中的应用

从PcBN刀具的切削性能、切削力的特征、锯齿形切屑的形成机理、金属软化效应、已加工表面质量以及刀具磨损机制等方面介绍了PcBN刀具在硬态切削中的适应性研究方面的进展情况,以期引起重视．充分发挥PcBN刀具的潜在性能。     

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。     

力反馈对中超精密球形转子研磨方法

为了获取高质量的超精密球体对四轴球体研磨机进行了改进。由于金属波纹管联轴器兼有传递运动、施加压力和导向功能，在机器的浮动轴结构中采用了这种联轴器。在研磨轴布置了压力传感器获取轴向压力信号，实现各轴压力的实时监测与控制。改进后可以使球体工件更好地对准理想中心，有效地减小了形状误差，而分级控制策略提高了自动化加工效率。磨削实验表明加工球体的表面质量得到较大提高。     

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.

     

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.     

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.     

Planing of Norway spruce with very varied ring width

A way of defining a “machining ability” is proposed. Cutting forces: The samples from the slow grown spruce give well known results. In this case the cutting forces are linked with specific gravity by a linear relation. For the samples coming from the fast grown spruces (A), there is no significant relationship between the cutting forces and the specific gravity. These different behaviours are illustrated by the aspect of the chips produced by both batches of spruce. Dimensions scattering. Analysis shows clearly that distributions of dimension quality are similar for spruces A and B. That means there is no compression in the thickness of the samples (z axis). Surface, roughness: More than one roughness criterion is needed to describe surface quality. The 8 criteria used in this work describe the vertical distribution of the roughness measurements. For all the samples, best results are measured on A sample.     

带式夹送淡水鱼剖鱼机的研制

依据鲢鱼的结构特征和对产品品质的要求,研制了一款带式夹送淡水鱼剖鱼机,并以鲢鱼为试验对象进行了剖鱼试验。该剖鱼机由机架、夹送系统、剖切系统组成。夹送系统皮带间距、皮带转速、剖切系统刀盘高度等关键部件工艺参数均可调节,配套功率共为3.7kW,其中剖切系统电机1.5kW,夹送系统电机2.2kW。以(1.50±0.25)kg鲢鱼为剖切对象所进行的试验结果表明:皮带间距对进料、剖切、出料均有显著影响,皮带间距40 mm时,可以实现100%顺利进料、平稳剖切和顺利出料;刀盘高度则对剖切质量影响显著,从鱼头到鱼尾完整剖开鱼体要求刀盘高度不高于190mm,完整保留鱼鳔要求刀盘高度不低于210 mm,不破坏鱼胆要求刀盘高度不低于180 mm。皮带间距取40 mm,刀盘高度取180~190 mm时,剖鱼机运行稳定且剖切效果最优,处理速度可达1 200尾/h。